Disclaimer: I am not completely unaware of the intricacies of voting systems, but there’s a lot that I don’t know.

Once upon a time I was a fan of ranked choice voting, but I’ve decided that for a single-winner election we would be better off switching to a primary+runoff where the primary is done with approval voting, and the runoff (between the top 2 from the primary) in the usual way.  Understand, I am in no way a fan of the first-past-the-post status quo, I merely think that we ought to seriously consider another alternative.

There are three reasons.

First, complex ballots are a problem, and people can screw them up.  A ranked choice ballot is more complex and there are easy ways to get it “wrong” so that you no longer have a valid vote, and then what happens?  There’s also many more bubbles to mark — if 5 candidates, 20 choices, of which only 4 may be marked.  Approval voting, 5 candidates, 5 bubbles, you can (sensibly) mark as many as 4 or as few as 1.  Screwing up one bubble leaves the others still valid, whereas screwing up one bubble on a ranked choice ballot may invalidate the ranking.

Second, the process of tallying up the vote is complicated and difficult to explain.  I’ve seen the explanation, and I agree with how it works, but it is complicated and plenty of people will be confused by it, perhaps not trust it.  Approval voting is easier to explain; each candidate gets the number of people who thought they were “okay”, and the primary will be between “most ok” and “next most ok” from the approval vote.

The combination of these two problems means that sore losers may challenge elections, and it will be difficult to convincingly demonstrate that they are just more losers.  (Of course, Republican sore losers will challenge any result that does not go their way, but with a simpler system, they’ll look more ridiculous). More ballots will be spoiled, and recounts will be tricky and annoying.

Third, approval and 2-way runoff have the property that counting can be split by precinct, and then the sub-results combined.  Ranked choice doesn’t work that way; reasoning about partial results is far harder.

One thing that I think inclines people towards or against ranked-choice is different models of voter motivation.  One advantage of ranked choice is that expressing a secondary preference does not harm your first choice (or so I understand).  If I like Alice then Bob, then Carl, I just express that preference, my 2nd-choice vote for Bob does not harm Alice’s chance.  This is very important to some people.  In contrast, in approval voting, if I “approve” both Alice and Bob, that vote for Bob may reduce Alice’s chances; if voters are focused on a favorite candidate winning (“Alice or bust!”), this may lead them to try to do the sort of strategic voting that we hate in the current First-Past-The-Post system (“I really like Alice, and Bob and Carl are both okay, but I think a lot of other people like Bob so I’ll only vote for Alice, and Carl just in case”).  On the other hand, if your goal is just to get good candidates into the runoff, then you’ll vote for anyone who doesn’t suck.  And if you wish to merely vote against a particular candidate, approval voting makes that easy, just vote for everyone but the bad guy, where ranked choice might require more strategic thought.

There’s another alternative voting system that is more expressive than approval voting and shares some of its good properties, and dodges Arrow’s Impossibility Theorem.  Instead of approving or ranking candidates, voters assign “scores” to candidates, for example, numbers between 0 and 9, subject only to limits on the maximum and minimum scores.  This is called “score” or “range” voting, and its proponents are very enthusiastic.  Tabulating votes can be done in parallel, and it is harder to spoil a ballot, though the ballot is more complex than an approval ballot.  The difficulty, to me, of score voting is that it is hard to reason about what a range of scores means — if I prefer Alice to Bob to Carl, is that 9-8-7 or 9-5-1?  Do I have an easy way to measure my hypothetical satisfaction?  I suspect that it many cases it may devolve to 9/0 approval voting.  One advantage of score voting is that it can be done in a single election; one disadvantage is that it might be vulnerable to accusations of “complexity” or “voter confusion”, though not as much (in my opinion) as ranked choice voting.  Wikipedia calls these “cardinal voting systems”.

Hello all, you are probably unsurprised to hear this from me, but I like the new bike lanes on Concord Avenue. I ride on them at least 6 times a week (5 days to/from work, plus farm share from Farmer Tim on Sunday), and they reduce stress even for someone as accustomed to traffic as I am.

I was also pleasantly surprised at the quality of the pavement; there are a few imperfect spots, but it is not as bad as I had thought it might be, and I would not hesitate to recommend it to other people.

I’ve heard through the grapevine that people now parking closer to traffic feel that is not comfortable to get in and out of their cars, and why yes, I have biked in that same space many, many, many times, I can see how they might feel that way.  That is sort of the whole point of a protected bike lane, reduce exposure to traffic.  Drivers newly exposed to traffic may feel this rather keenly, but it is a constant risk to someone riding on a street on a bicycle.

One reason to have such a bike lane is that it reduces the overall person-minutes of traffic exposure; it is a net win for that problem. Here are some measurements and estimates that I hope demonstrate this.  I timed myself this evening traveling from Baker to Orchard, and it took 2 minutes. I also experimentally got in and out of a car parked in our driveway and walked around it, and I was easily away from the side of the car in 15 seconds either entering or exiting. That is, each person on a bike traveling that stretch of road is exposed to about 4 times as much passing traffic as someone entering or exiting a car (2 minutes versus 15 seconds to enter plus 15 seconds to exit). If I had to guess conservatively, I’d say that (in one direction) there’s at least 15 bikes per hour between 8am and 10am and again between 5pm and 7pm (60 bikes), plus (really guessing) at least 5 bikes per hour between 10am and 5pm (35 bikes), for a total of 95 bikes, for one direction. I base my rush hour estimate on seeing at least one bike moving in each direction almost every time I commute on Concord Avenue, and they are as much as 2 minutes away from me, and I don’t count because I am the observer, so bikes are 4 minutes apart at rush hour, or 15/hour. 95 bikes times 4 is 380 — if fewer than 380 cars park on one side (or the other) in a given day, then the protected bike lanes result in less traffic exposure. I counted parking spots from Baker to Orchard on the north side (which has more spots) and got 57.  380/57 is 6-and-2/3 — unless the average weekday parking traffic per spot is over 6-and-2/3, we’re better off (fewer people-minutes of traffic exposure) with protected bike lanes. I don’t think there’s that much traffic in those spots. I suspect that the average weekday cars per space is closer to 2, so I could be off quite a bit in my estimates and the protected lane would still be a net win.

This is also just raw traffic exposure, ignoring dooring risk, and assumes that someone parking their car gets in or out of their car without waiting for traffic to clear; time is time, they’re exposed for 15 seconds. Actual cautious-driver behavior reduces this risk whenever there’s any gaps in traffic (it’s easier to find a 15 second gap, than a 2-minute gap).  There are caveats and quid-pro-quos, but none of them results in winning arguments against a protected bike lane; for example, in the old configuration, if no cars are parked, then I would often ride through parking spaces (where the protected lane is now) to increase my distance from traffic — but if no cars are parked, people aren’t exposed to traffic parking their cars.  Or, if there is very high turnover per space, yes drivers are more exposed, but then the risk of dooring becomes high enough that it cannot be ignored.

I do sympathize with people who think parking is unpleasant, and that’s one of the reasons I ride a bike instead — I hate parking, too.  I’m not young, I’m not thin, it’s not a short commute, I do this year round, I keep waiting for more other people to realize that they could do the same.  A protected bike lane removes one of the frequent and otherwise intractable objections that many people have to riding a bike around here.

A friend of mine long ago told me that I forget that most people don’t know what I know, and don’t figure things out as quickly.  And even so, it took time for me to figure things out, I know of things that were right in front of my face for decades, and I did not notice them.  So, after over 40,000 commuting and errand miles on cargo bikes since 2006, and as someone who has more than one copy of Bicycling Science, as well as my own personal copy of Food, Energy, and Society, here’s some stuff about bikes that I’ve learned and other people appear to be less clear on.

Stopping power, turning ability, bike geometry

The physics behind the numbers below is discussed, in detail, in Bicycling Science.

A useful thing to know is that rubber on road has a sticking grip force that is about the same as the force against the road, for dry pavement.  That means that a vehicle that is low enough to the ground that it will not flip will have a maximum deceleration before it skids of 1g (g = earth’s gravitational pull), or 32 feet per second-squared (9.8 meters per second-squared, or 22mph per second).  That is, if you are in a car traveling 22mph, the quickest you can possibly stop is one second (your speed decreases by 22mph per second of 1g braking), and in that one second you will travel 16 feet (the formula for distance traveled is x = v0t + 0.5at2), t is 1, a v0 is 32 ft/s, a is -32ft/s2, so 16).

On a “normal” bicycle, two things limit this.  Because the rider is most of the mass and is positioned relatively high, before the front tire exceeds its grip on the pavement, the rider will instead rotate over the front of the bike onto the road.  This occurs at about 1/2 g. A corollary of this is that it’s not a great idea for a cyclist to tailgate a car; if the car stops hard, the cyclist is physically unable to stop as quickly without being flung onto the pavement or the back of the car.  The exceptions to this are bikes where the center of mass is further back; a tandem with two riders, or a box bike, or a long-tail cargo bike that is also well-loaded to the rear.  On the other hand, a penny-farthing or high-wheeler, where the rider is positioned almost on top of the front axle, has very limited ability to brake without flipping.

The other problem is that even on differently designed bicycles where the rider will not flip, because a bicycle rider uses their front wheel for steering, when it goes into a skid it becomes very likely that the bike (and its rider) will fall down.  This is not guaranteed, and with years of experience I have survived such skids once or twice, but the first time I had a front wheel skid I hit the ground so fast I was down and in pain before I realized what had happened; it’s much faster and more violent than a rear wheel skid.

A further problem is that stopping quickly requires a fair amount of arm force to keep you on the bike, and in the worst case you’ll just keep moving while the bike stops underneath you.

Rear-wheel braking is slower yet; because stopping shifts your center of force forward, it reduces the force on the rear wheel, which if it is the braking wheel, will have less road grip.  On a normal bicycle this limits rear wheel braking deceleration to about 0.25g, whether you do it with a caliper brake, coaster brake, or by jamming your legs on a fixie.

In theory (not to be confused with practice), a skilled rider with enough spare room on the road could turn their (normal) bicycle with a full g of centripetal acceleration in the same forward displacement needed to stop it (with 1/2 g of forward deceleration).  (Math: for centripetal acceleration, the radius of the circle is v2/acentripetal; for forward deceleration, the distance to zero velocity is 0.5v2/abraking; however because a normal bicycle can turn twice as hard as it can brake, the circle radius and stopping distance are equal.)  HOWEVER, in practice this would be stupidly risky, because it does not reduce your kinetic energy and if you fail (failure is always an option) the resulting crash will be far more dangerous.  This daring maneuver also requires much more clear road space than simply braking.  And, on a tandem or cargo bike of any sort, the longer bike’s improved braking ability beats its unimproved ability to turn.

Perception and reaction time

Bikes lack stopping power, but for most people on bicycles (upright bicycles, rider not wearing headphones, not seriously impaired hearing) a person on a bike is far more able to perceive what is going on around them.  They are (usually) seated higher, don’t have an additional layer of glass in front of their eyes, or supports for that glass obstructing their view, or bulky hood hiding who knows what, and don’t have the noisy engine or layers of acoustic insulation obscuring sounds around them.  And, because the front of a bicycle is much shorter than almost any car’s hood (excepting front-box cargo bikes) their riders are able to position themselves far forward and look around corners.

Reaction times for bicycle riders seem better (from videos of my own reactions) than the norm assumed for drivers.  I think this is mostly a result of better human factors in the brakes; to stop a car, a driver must lift their food from one pedal, move it over, and depress a different pedal, whereas a cyclist with hand brakes can maintain their fingers over brake levers in traffic, and activate the brakes in a single motion.  I’ve measured real-world on-bicycle reaction times as low as 0.6 second, and some perhaps as low as 0.5 second (which through the camera lens, looks superhuman).  0.9 second, which is about the estimated driver reaction time, is what I get when I am distracted — it looks fine on the video, but at the time it felt like I had made an enormous mistake.  The failure modes for panic stops in cars and bikes also differ; on a bike, there’s a risk of a header from braking too hard, on a car the risk is that your foot will miss the proper pedal and you will accelerate instead.

There’s an additional problem related to cognitive load; if you’re actually evaluating everything within your stopping distance that could go wrong, as your speed increases, that distance increases, and it increases at a greater rate than the speed increase.  A driver traveling 30 miles per hour has 2.5x their stopping distance at 15mph; to understand what’s in front of them, they need to know 2.5x as much “stuff” about their surroundings, and they need to update that knowledge at twice the rate.  The same thing applies to someone on a bicycle, but common case there is 20mph or below, not even 25mph, so this is less of a problem (people biking should be really careful at “high” speeds like 30mph, because we have so little experience at those speeds; my time over the last 16 years traveling 12-20mph is measured in months, my time above 25mph is measured in minutes.)

The combination of better reaction time but lower stopping deceleration means that up to about 20mph, hand-braked bicycles and cars have about the same stopping distance, with bikes slightly ahead at 17mph and slower.  However, because people on bikes have much better perception and less cognitive load, they’re more aware of what’s around them and can make more sense of it.  A corollary of this is that to a driver, a cyclists’ choices may appear “random”, but this is because the cyclist is (often) acting on information that the driver lacks.  Just for example, if I hear a car approaching an intersection from the left, I may stop without ever looking in that direction, even if the right is obviously clear.

There are other not-obvious-to-drivers effects at work.  When stopped at traffic lights, because they take up so little space, cyclists usually are stopped at the front, and over time, can collect a lot of information about signal timings, local road conditions, and local traffic patterns.  This can mean things like “the walk signal comes 3 seconds before the green” or “the light is long to allow pedestrians to cross, the side traffic usually clears after 5 seconds and then it is safe to run the light”.

 Two wheels versus three wheels

People who have problems with balance or coordination can’t necessarily use a bicycle, and can instead use a tricycle.  For lower speeds, the tricycle is more stable because the center of weight sits well within its wheels.  At high speeds, however, tricycles become riskier to turn because most tricycles cannot tilt, and because they cannot tilt, they risk flipping.  This is not universally true; there are tilting tricycles, very-low-to-the-ground recumbent tricycles, and experienced riders can throw their weight around on the tricycle to counteract this effect, but these are not common case.

So, basically, three wheels is more stable at low speeds and easy turns, less stable at higher speeds and with rapid turns.

“Motor” efficiency

Bicycles are efficient for carrying one or two passengers because bicycles have small weight and move relatively slowly (both compared to cars), but viewed as a motor, we humans are only about 25% efficient; 75% of the food that we eat for physical energy, we turn into heat, and the food that we eat took energy to produce. Because humans are such inefficient motors, and modern batteries, motors, and their controls, are quite efficient, it is entirely possible for an e-bike to be the more efficient choice, depending on details:

  • Humans have varying diet; the more carnivorous someone is, the greater the energy cost of their diet (generally, there are further details, but meat tends energetically expensive).  But, contra that, what matters is the marginal calories, not the average calories.  When you exercise more, you may find yourself craving carbs more than usual, not lobster.
  • An e-bike, being easier to ride, will tend to generate more travel and thus consume more energy.  However, if that extra travel would have occurred in a car, then it is still a win.  An e-bike makes it easier to ride more quickly (up to 20 mph in the US), which is somewhat less efficient than riding at typical commuting speeds (12-15mph seems typical without e-assist).  However, if the alternative to a rapid trip by e-bike is a trip in a car, then again, it is still a net win.  Notice how in both cases, the unfavorable comparison is to a bicycle trip that might be purely hypothetical, whereas, if the actual other trip is in a car, the e-bike is far and away the energy-saving choice.

Another under-appreciated corollary of the wastefulness of the human engine is that we get hot and need the airflow that a bicycle provides.  Climbing hills is famously hot because our energy (and heat) output go up, while the speed of the cooling wind goes down.  Stationary bicycles tend to require fans.  And pedal-powered electricity generation gadgets are usually a bad idea; yes we get the exercise, but we also get very hot, will get extra-sweaty, and may require a fan for ventilation, and the fan is not energy-free.

A happy corollary of our wasteful human engines is that in cool weather it’s not that hard to stay plenty warm.  Our extremities still need protection from the wind (so, toes, fingers, ears) but everything else tends warm, after we have physically “warmed up” to the exertion.


This is a little odd, but one thing people miss is that when you bike there is a lot of airflow.  Yesterday I biked in 95F-ish temperatures, about 40-50% humidity, and as long as I was rolling, actual physical exertion in that heat was still comfortable.  Rolling along at 12mph, or 18 feet per second, I sweep through about 10 square feet of air (crudely, 2 feet by 5 feet), for 180 cubic feet per second of ventilation, or 10,500 cubic feet per minute.  That’s about 5 20-inch box fans on high, all aimed at me.  At the same time, in the winter, because of this airflow, one of the most important ways to stay warm is to block the wind.

Double-counting bicycle time.

Because humans are not the finest motors, and because some (tasty!) food has a high energy cost, in some cases the end-to-end miles-per-gallon of a bicycle can be as bad as some fossil-fueled automobiles.  However, up to at least 100 miles per week, we get to double-count time/distance on a bicycle as exercise; time spent on the bicycle is time not spent at the gym, and calories burned on the bicycle are calories not burned at the gym.  So for example, five days each week, I get about 30 minutes of exercise before and after work, and then in zero time spent and zero energy consumed, arrive at work.  (To be fair, that is a lot of exercise, but it’s not wasted; there were measurable changes at my annual physical, worse from the low-commute Covid year, and then recovery to the better place in the next year.)  Energy expended at the gym also incurs a ventilation cost; to cool you down, gyms tend to be air conditioned and often include fans, where each fan consumes 50-100 watts.

And, the same as when you drive, you can also listen to podcasts or books on tape while you bike to work.

Typical speeds

People sometimes make wild estimates of bicycle speeds.  Cyclists who can cruise at 25mph are not common; well-trained cyclists can, but most people are not well-trained cyclists.  Even cruising at 20mph is not that common; I could, as a teenager, but it took a lot of practice, and I can’t do that now.  Sprints are faster, but similarly limited.  E-bikes come with various limits; the US federal law specifies two speed levels for assist, 20mph (still a bicycle) and 28mph (a “type 3” e-bike).  California state law uses these same rules, I think that this is the general plan for new e-bike legislation, especially the 20mph part.  But, for federal law purposes, if the assist can propel you faster than 28mph, then it is not a bicycle, at all.

Cargo capacity

Most people have a poor intuition for how much you can or cannot carry on a bicycle or a trailer.  Far and away the most important factor is the interaction of loads and hills; the greater the load, the smaller the hill that you will be able to manage.  Very low gears make hill-climbing with larger loads possible, but every rider has a minimum speed at which it becomes very hard for them to balance a bicycle, and there are physical limits on drivetrains.  On a cargo tricycle, however, balance is not a problem, only the torque limits of the drivetrain.

A second problem is managing the ability to brake; default bicycle brakes are sized for a default bicycle load.  Larger disk brakes and drum brakes help with this; managing downhill speed also helps with this.

On flat ground, the main limit is the rider’s ability to handle the load at very low speeds.  As the load gets heavier, more time is spent at low speeds, and the harder the load is to rebalance.  In practice I can pretty easily start and balance a load that weighs about as much as I do (over 200lbs), but I have also seen a video of someone riding a cargo bike loaded with 500lbs of bananas, and they needed help to get started.

Using a trailer avoids the balance problems, though the hill problems remain, and braking can be more difficult depending on how weight is distributed on the bicycle and trailer.  

Weird rules

Your intuition about what is or is not a “bicycle” may not agree with the law, which in turn depends on where you are.

The rules about what is a legal bicycle are a little odd, sometimes devolved to the states, and tend to differ in important ways from Europe.  So, at the US federal level, a “bicycle” is defined by its power and number of wheels; if it has no assist and 1, 2, 3, or 4 wheels, it is a “bicycle”.  If it has up to 750 watts of inhuman power assist, its assist is limited to 28mph, and 3 or fewer wheels, then it is also a “bicycle”.  There appears to be no US federal limit on “bicycle” width or weight.  But, if it has an e-assist propelling it faster than 28mph, then that is not a bike, that is not an e-bike, legally, that is some other device.

However, at the state level, there are a variety of rules and regulations, with a variety of e-assist power and speed limits.  California has rules that conform to the federal standards, with additional use requirements on so-called “type 3” e-bikes that have assist past 20mph.  As of this writing Massachusetts treats them as mopeds, though that may change within a month. New York State has a 36-inch width limit on cargo bicycles, with a bill proposed to increase that to either 55 or 48 inches, but that bill also includes a lower speed limit (12mph) and insurance requirement for e-cargo bikes.

Rules in the EU are more detailed and still evolving. Older rules limited assist for cargo bikes to 250 watts, which is completely inadequate for actual cargo in hilly places.  Four-wheeled e-bikes and e-cargo-bikes are legal.  The new rules allow more assist, but also have detailed remarks about brakes and bicycle durability.  As of that cited document, EU rules were silent on width, but Germany’s DIN has proposed regulations — 1m width and 250kg for 2-wheels, 2m width and 300kg for 3 or 4 wheels.

How to bike in Cambridge and Somerville (and perhaps other places)

Goals are safety, low stress, harmony with pedestrians and other micro mobility users.  This is informed by my experience biking through Belmont, Cambridge and Somerville daily for the last seven years, and biking through Belmont, Arlington, Lexington, and Burlington for nine years before that, recently exceeding 40,000 miles of commuting and errands.  I’ve also been biking long enough not just to have made mistakes, but to see patterns in my mistakes.  I collect a lot of video, note the sketchy bits, and sometimes review them.

I intended this to somehow not be as heavy-handed as I know it is, but this afternoon I was sitting on my bike on the sidewalk next to a bike lane, and as a pedestrian stepped into it to get to their parked car, the oncoming bike dealt with this by yelling “head up heads up heads up” instead of, say, slowing down.  This is exactly wrong, for reasons detailed below.  This whole thing has been bouncing around in my head for a while.

And, also, this is not the “best way” to increase safety and comfort, this is merely what you can do on your own.  Better regulations and better road design are both better choices than solo safety, but solo safety  doesn’t need focus groups or community meetings to approve it.

Edit: A second opinion, from a local Twitter friend who I hope to someday meet IRL. Scan down past my reply on Twitter for commentary. Some of the remarks will be interspersed below, in italics, either for emphasis or missing perspective.  One general problem is that the discussion of panic stops and stopping distance is not right, it could be better, but neither of us quite knows how. One particular issue is that “panic” stop is old-biker jargon; it means a really fast stop, which is a useful skill. Another issue is that the math is distracting, and the choice of numbers is not well justified. The TLDR summary of that flawed section could be: don’t ride too fast, learn to stop quickly, react sooner, not later, be aware that you can go over the handlebars if you stop too fast, so definitely wear a helmet when you practice stopping.  And, I didn’t say it because it’s as obvious as the nose on my face, never tailgate a car.  Bikes have a reaction time advantage, but cars have a braking ability advantage, and if they stop for something you can’t see (or out of malice), you have no reaction time advantage. Probably deserves its own discussion.

Existing traffic law is a poor guide

I don’t mean that you should ignore traffic law, and you certainly have to be aware of laws, but only obeying traffic laws will leave you exposed to various unsafe situations, and in some cases breaking traffic laws can lower your risk, principally from turning traffic, especially trucks.  Too much focus on the law causes you to think about blame, not mitigation, and any time spent analyzing a situation from a legal point of view (“is that pedestrian jaywalking?  If their foot isn’t in the road yet, am I really required to stop?”) is time spent not thinking about how to reduce risk.  No you cannot multi-task as well as single-task, the goal is to make the safest choice the habitual choice, and legal analysis gets in the way of that.  If you’re thinking about safety, your first thoughts should not include “what is the traffic law?”

For more on the ineffectiveness of blame, see Jesse Singer’s book There Are No Accidents and also the discussion of maritime versus airline safety in Charles Perrow’s Normal Accidents.

Practice safety and prevention

And by “practice”, I don’t mean, “be constantly stressed about”, but instead, cultivate good habits, make your usual behavior be the safer behavior, and make your snap reactions be the safer ones.  You’ll make mistakes sometimes anyways, but you’ll make fewer mistakes.  (I made a mistake today, I apologized a whole darn lot to the pedestrian that I did not hit.)

  • Look for “I’m about to ride where I can’t see what’s coming” situations, and be prepared to stop quickly and completely.  Properly designed infrastructure ought to make these rare, but, ha-ha, this is a guide to biking in Cambridge and Somerville.  It’s common for us to have loading zones with trucks in them completely blocking the view of a crosswalk or intersection.  Someone might step or drive out from behind that truck (I have video).
  • Learn to pass behind; whether cars, other bikes, or people, they all tend to start or keep moving forward more often than moving backward, passing behind reduces the chance of a bad interaction, and removes the need for a negotiation about who goes first or speeds up or slows down.  It’s just simpler.  Another reason:
    “The passing behind advice: good, but I also prefer keeping a bad driver in front of me vs me in front of them; if they’ve done one dumb thing when I could see, I assume they do dozens more dumb things every hour. If I’m behind them then they’ll have a harder time affecting me.”
  • Train yourself to react to emergencies by braking first, and practice braking so your panic stops don’t turn into headers.  Upright posture helps with fewer headers, so does a heavy bicycle, especially if it is loaded to the rear.  Braking even a fraction of a second early can make a big difference; an extra half second at half a g (a best-case hard front wheel brake) can cut your speed by 8 feet per second, or over 1/3 at 15mph (15 mph/22fps -> 10 mph/14fps). The goal is not to be tense about this, but just to turn it into a habit, so that your snap reaction is the safer one.  Swerving can also work but swerving requires that you not swerve into something else — this is more complicated that braking.
  • When in doubt, slow down. It’s a mistake to try to “zip past” a sketchy arrangement of cars and pedestrians.  Doing that just adds to the sketchiness, adding speed makes crashes hurt more.  This is a hard habit to break.
  • Don’t treat your bell as an emergency safety device.  Brake first.  Don’t try to convince yourself that you can do both just as well as one, no, you cannot.  Bells are low-bandwidth, useless for signaling drivers (their cars make them deaf), and pedestrians aren’t required to be listening, able to hear you, or paying attention.  Braking is one reaction time away, bell-ringing means the response is at best two reaction times away.
    “Also triple OMG yes about bells. I think bells are good for a quiet path when you’re like 100 feet away. If you’re close enough to talk, do that. Jeez. Instead dudes (almost always dudes) think it’s a “GTFO” signal.”
  • Don’t expect other people to do more than obey the law.  Don’t delude yourself with expectations of what other people “should” do (should control their dog “better”; should not wear earbuds; should wear reflective clothing at night on a shared-use path; should pay more attention to their toddler).  Those things are not even the law, why would you expect people to obey not-laws when they break actual laws often enough?
  • Slow and wide for pedestrians everywhere. In a bicycle-pedestrian crash, the person on the bike is at greater risk, but it’s them that brought all the energy to the crash, not the pedestrian.  Pedestrians are inherently safe, even more so than bicycles.

 Don’t optimize for top speed

This is not obvious if we just react to how we feel about being passed, especially close-passed, but if you are merely bumped by a passing car or truck and lose control, higher speed is not on your side.  You can also see this by looking at relative trip risk between motorcycles and bicycles; the per-trip risk of death on a motorcycle is TWENTY-FIVE TIMES HIGHER, despite the louder pipes, despite the brighter always-on headlights, despite the greater mass and stability of the motorcycle, despite the better and in-most-states legally-required helmet.  There is a speed somewhere between typical bicycle speed and typical motorcycle speed at which adding speed makes things more dangerous, not safer.  It might not be a very high speed, maybe as low as 25mph, maybe a little less.  I think it is telling that European E-bikes are assist-limited to 15mph; the Europeans are much better at road safety than we are, and they chose 15mph, not 20mph.

Higher speeds hurt in several ways:

  • Drivers aren’t expecting bicycle speeds above 15-20mph; they will be surprised, perhaps angry, perhaps unsafe.  You will have a better experience at a slightly lower speed.
  • Crashes get much worse between 15, 20, and 25mph.
  • Stopping distances increase dramatically with speed, even bicycle speeds.  My best-case stop at 15mph (0.6s reaction time, 0.5g braking) is 28 feet; at 23mph, it’s about about double that.  Braking more sedately (0.25g, a skidding rear wheel), 15mph results in a 43 foot stop, 20mph needs 71 feet, 23mph needs 91, and 25mph, 106.
  • That stopping distance is the minimum you need to scan for surprises; you can do a much better job of that when it’s 30 feet, than 60 feet.
  • Resist the urge to attain maximum speed down a hill.  Instead, bust your ass on the way up (on a commute, that produces the maximum time savings for a given amount of sweat) and rest and recover coasting downhill. But beware “workout brain” clouding your judgement after a hard hill climb. (Yes, this is a real thing.) 

“The part about speed is good, the analogy to motos is great and you should press the point about ebikes more IMO.

I disagree that drivers aren’t expecting bikes to go above 15-20mph, I think it’s more like 10-15 just based on interactions. ¯\_(ツ)_/¯”

Identify and avoid bad roads and dangerous vehicles

  • Multilane roads are a bad idea.  Drivers are more distracted because there is more going on, some of them will use the second lane to drive fast and/or accelerate unpredictably.
  • Door zone bike lanes in non-residential areas are a bad idea;
    Door zone bike lanes in permit-parking-only are less risky;
    Pay attention to folded-in mirrors (good), lit brake lights (bad), Uber/Lyft stickers (bad), and taxis (bad) and cars with New York “T&LC” limo plates (very bad);
    Riding fast in the door zone is a bad idea.
  • Trucks with large exposed wheels are deadly.  If you don’t feel comfortable with one approaching, leave the road.  Don’t depend on the driver, their truck is not designed for your visibility or your safety, they may not see you (and that’s certainly what they’ll claim if they hit you, and the police will believe them).  Yes, the whole situation is completely appalling, European regulations make big trucks somewhat safer, but in this country we have other priorities.

If you got this far, thank you for your patience.

A few years ago I started playing with a laser cutter in a “maker space”, and the thing that I have had the most luck with was chain guards for my bicycles, to help keep my pants slightly cleaner.  I made one out of mirrored acrylic which looks Very Flashy, but the acrylic is not that durable.

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During Covid, I lost access to the maker space, and needed a new chain guard for one off my bikes, so I went and ordered one in 3mm acetal from Sculpteo, and it has worked very well.

I don’t recall if I sent them a PDF or a SVG, but it was one of the two.

Anyhow, my chainring was creaking, some of the chainring bolts were working loose, so this seemed like a good time to take it all apart, tighten things up, and take some pictures.  Obviously the chainring needs some parts to hold it together, and these are shown here.

First, mounted on the bike.  The gap for the crank arm makes life very, very easy, compared to the aluminum ones that usually come with bicycles.  

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This is my spare copy (I ordered two, shipping for two was as high as shipping for one).  Notice all the little spacers in the waste section in the center; those will be useful later.

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Here is the old one, removed, with screws and washers still in place, and all the spacers in the box below.

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To reinstall, use tape to hold the screws and washers in place, then put a pair of spacers (each is 3mm) on the backside.

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Here I’ve tilted it the other way so you can see the spacers.

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Insert the long skinny screws through the center holes in the chainring bolts, and spin the little nuts on the backside so the screws won’t come out, remove the tape, and crank them down pretty tight (because acetal is tough, unlike acrylic).

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To the Belmont Select Board,

I am writing to support the proposed parking-protected bicycle lanes on Concord Avenue. I believe these will make it safer and more comfortable for most people to bike on Concord Avenue and attract more people, especially students, to use a bike instead of arriving at the schools by car. I have biked on Concord every working day, year-round for the last seven years, so I know the road well and especially its risks from a biking point-of-view.

Parking protected lanes would increase safety in at least two different ways: removing risks from swerves (either bike into car or car into bike), and dooring risk. Some dooring risk remains, but the left (driver’s side) door is the one most frequently opened from a parked car, so riding on the right side of a parked car is safer. Riding on the right side also means that in the event of an abrupt door opening, all the other obstacles are stationary and will never be a large truck with exposed deadly rear wheels.

Obviously, having surer separation from traffic makes the ride more comfortable. With luck, more middle and high school kids will use these lanes to bike to/from the middle and high schools instead of driving or bothering their parents for a drop-off by car, thus reducing traffic jams during the school rush.

These new lanes will inconvenience some people. Turning onto Concord from a side street will be more difficult because it will be somewhat harder to see oncoming traffic. Cyclists whose primary goal is speed may find themselves less able to pass other, slower, cyclists (in Cambridge and Somerville, this is just how things are at rush hour, so I have ample experience as both delay-er and delay-ee). These problems, however, are of a different and lesser category than personal physical safety.

We should also recognize that some of these abutter convenience compromises are themselves the result of other compromises; if we did not care so much about minimizing the number of lost parking spaces, we might instead construct a bidirectional protected lane (using Jersey barriers, perhaps) on the north side of Concord Ave along Clay Pit pond and the high school. This would not only leave the south-side abutter experience unchanged, it would also provide easier passing for higher-speed cyclists, remove turning risks from the south-side streets (either right-hooks from Concord onto the side street, or T-bones from the side street onto Concord), eliminate the right-side door-zone risk, and provide a guaranteed-available route for emergency vehicles (wide bidirectional bike lanes are used for this purpose around the world, including even in Cambridge, I have video). To be blunt, a whole lot of advantages, including safety advantages, were traded away for the purpose of preserving parking. We like parking a whole darn lot here in Belmont, otherwise we’d make different choices.

One place where the current plan is particularly lacking, and may want future improvement, is on the stretch of Concord approaching the Post Office and underpass. There, a bidirectional north-side lane would be a lovely safety improvement, but I don’t know how to reconcile that with the obvious need for short-term parking, especially handicapped access parking. It is, however, the most dangerous and least comfortable stretch of Concord (the very same short-term parking that is so necessary, also creates a dooring hazard, and the underpass is an abomination from the point-of-view of comfortable, safe biking). I have some hope that the Alexander Avenue tunnel under the railroad tracks, when completed, will provide a suitable alternative for safe, low-stress bicycle access to the Winn Brook neighborhood and Belmont Center from the high and middle schools.

Assuming we create these protected lanes, one detail that would help is to check the pavement for flaws and irregulaties, and correct those. I’ve recently looked at the road where the protected lane will be, and what I could see looked generally okay, but there’s a few spots that could be improved. Potholes are a surprisingly common cause of bicycle crashes, especially for less-experienced riders.

David Chase

So, I ride a cargo bike most of the time, have for about 15 years and 38,000 miles, I sometimes forget that lots of people only have experience with “normal” bikes (or worse, only with a car), and just work with that knowledge.  And I end up explaining this stuff, or parts of it, over and over again to people who think they understand what a “bicycle” is and what its “limits” are.

Read the rest of this entry »

I tried to take pictures of each step along the way.  The goal here is to make a durable, “washable” (soak in boiling water, or alcohol; I don’t think detergent is good) mask that filters very well and also breathes pretty easily, seals well, will not collapse if you breathe hard, and muffles your voice somewhat less.  I tried making one of these with no fabric, just filter material, and that is not strong enough to last; the interior layer is necessary (and feels nicer on your face).  The filter media I use here filters well — it looks good on paper, and when the west coast smoke blew into Boston, it stopped the smoke smell (it does not stop smaller smelly molecules).  For reference, from that paper, here’s the graph of filtering effectiveness and breathing resistance (which is high).  It’s the pink lines at the top, just under never-washed N95:

Mask material reuse

The difference between this material, and medical N95, is that those use electrostatic charge, which is magically good till it wears off because you washed it (note that this chart quits at half a micron, so it is not the whole story).  Not using magic electrostatic properties means that the filtering survives exposure to alcohol, but also that the breathing resistance is much higher.  Nonetheless, I manage, most other people should as well.

The mask is shaped like a duck bill, beware, and there’s a tradeoff between area (ease of breathing) and volume (rebreathing of CO2).  The pattern itself is parameterized, so that you can adjust its size somewhat for your own personal face and your own personal preferences for ease of breathing vs rebreathing CO2 (we have varying lung sizes) vs ridiculous appearance; I put a program on the web to do this; it creates the pattern in two halves, which you print on card stock, cut out, and tape together (as seen below).  I’ll update it from time to time; notice how the pattern below printed “elastic” in the wrong place (fixed), labels one of the darts wrong, and I really wish it had a QR code that would let someone reproduce the mask without retyping parameters.

This is the 4th iteration of a design that started with one from the UF School of Anesthesiology.


  • Cummins Filtration EX 101.  This comes in packs of 50.  I can send smaller quantities to friends and family, the rest of you have your own friends and family.
  • Heat shrink tubing for capturing wire ends in the nose wire, and for holding the coffee stirrer nose brace together.
    2:1 shrink ratio, 90 degrees C activation, 1/8”, 3/16”, 1/4” (I use NTE clear from Digikey).  You can use tape for the brace joints, and if you have some other way of making a nose wire, you don’t need this.
  • 5.5” Coffee stirrers (Amazon link) for the nose brace.
  • Wire for nose wire (I use 19-gauge copper wire that I rescued from the side of the road after a lawn mower ran over a phone wire bundle).  I did once try 19-gauge stainless wire from the hardware store, it is not comfortable.
  • Cord/shoelace and cord lock for neck strap.
  • Elastic for head band.
  • Fabric — I use linen or hemp for the interior, whatever for the exterior.  Goal is both should breathe easily (the filter does the filter work), interior should be strong enough to deal with cords and braces, exterior (which is actually optional) should protect the filter from abrasion, perhaps have an appearance.  So while you can use old T-shirt for the exterior, it’s probably wrong for the interior because it is too stretchy.

Photos of steps (high-res album version):

Nose wire first.  This is 9.5 inches of copper wire, alternately use 2 pieces 4.5 and 5.5 inches long with the longer wrapped around the ends of the shorter.  To bind it all together, use heat shrink tubing, fold in a piece of fabric, then apply an iron, blast a few times with steam.  It will stick slightly to the fabric, which is why you wrap it in fabric because that is better than sticking to the iron or the ironing board.

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After doing the ends, also.

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Filter media and pattern.

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Pattern just fits the filter media, this is by design.  For the filter, don’t bother with any flaps or tabs, and don’t do the darts yet either.

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Foreshadowing: this is the ultimate destination of the nose wire.

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Pattern traced.

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Pattern cut, precisely around the face, with slop around chin and nose, to be trimmed later.

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Pattern on the interior layer, which gets all the tabs, flaps, and alignment marks for the elastic and cords.

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Cut, again with some slop.  The flaps will fold down, and then iron to make it easier to sew.

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Exterior layer, which is a used tie-dye T-shirt.  No marking for cord attachment or tabs. Cut this with a fair amount of slop.

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And cut:

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Here’s an extra bit of more T-shirt to go inside the nose-wire flap, to help cushion the nose.

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Sewing the nose wire flap.  This is the only place where pins are appropriate, once the filter is in the mix, use clips instead because holes in the filter are to be avoided as much as possible. I have access to nice clips because my wife sews very well and my mother-in-law is a fiber artist (it was her that sent me the original pattern from UF) but bulldog clips get the job done and I have also used those.

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Sew along the bottom to leave a channel.  This will get narrower when the filter and exterior are sewed to this.

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Trim away the excess.  It doesn’t need to be super pretty, nobody will see this.  The nose wire goes inside, just shown here on the outside to show how it will be positioned.

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And with the pockets sewed.  These will also be sewed across the bottom, later.

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Recipe for stacking the layers.  This part is important, I copied it from older instructions for another pattern.  Steps will appear below.  The filter “outside” has more dimple-y dimples, bright light helps for telling them apart.

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First put the interior together, using clips to get the cords positioned right.

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Align the exterior layer on top; it’s good to get the patterns aligned for later, but this one is mostly for show, and excess will be trimmed soon.  One problem with too much extra fabric is it gets in the way of aligning the filter (one top) and the interior layer (own the bottom), which is what really matters.

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Carefully position the filter.  Goal is that its face edge (the part that curves up, around, and down from left to right) is well-aligned with the interior layer at the bottom.  Apply lots of clips to keep everything from shifting.

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One big stitch from lower left around the top to lower right.  I take my time.  It just now occurred to me, if I had no machine, could I sew this by hand, and I think the answer is “yes”.  It would be tedious, but it is entirely at the edge and I think you could whip stitch it, just fold the exterior up and on top and bind it all together.  I might start in the middle and then go to one edge, then the other.  The pockets and nose flap would be more work, but you can use more fabric there and take your time, that’s just sewing fabric.

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Use fingers to keep everything moving together, don’t want cords to shift.

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Done, from the top of the stack. (Links to high-res)

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Done, from the bottom of the stack. (Links to high-res)

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Prepare to flip interior around.

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Flipped, looking at interior and cords.

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NOW use the pattern to put the darts on the mask.  Align the pattern with the filter, which is hidden under the exterior in this photo.,

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I sew it somewhat more generously than the mark, probably ought to reflect that in the pattern.  Note that the clean side of the sewn dart goes against your face, for better comfort and better seal.  Design of this mask, most people won’t see the underside of your chin anyhow.

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Both darts done.

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This is the relatively tricky part and is probably subject to some further improvement.  The two chin edges need to be brought together, and then sewed.  I’ve left the pattern un-cut in the nose because there is always some imprecision here and this lets me even things up at the nose.  The clip here marks where the sewing stops.

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Finish the chin with a stitch across the darts and the center.

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After sewing the chin, need to sew the nose.  The mark on the pattern shows where.

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After sewing across the nose, clip off the excess.

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Next need to make the nose brace.  This is pretty much by eyeball, and I got the short one in the nose too long the first time.  I cut the coffee stirrers to length with some wire clippers, then use sandpaper to take off the sharp parts.

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To join the coffee stirrers together I use 1/4” heat shrink tubing.  I’ve also used gaffers tape, probably fabric adhesive tape would also work.  Again, wrap in scrap fabric and use a steam iron to shrink.

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I use two layer of heat shrink tubing — this is the completed brace.

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To fit, anchor the ends but do not fit the nose.  Put the not-in-nose angle in the chin, then push into place.  If this seems impossible, shorten as necessary.  If you need to shorten the center, either pull it apart or razor off the tubing.

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Brace in position.

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On my face. This is a lot of mask, I am trying to figure out how to fit a restraining thread through the middle of the bill to reduce its volume, that will still allow me to remove/replace the brace if I want to,  To wash this thing, take out the nose wire and brace, and either soak in boiling water or alcohol.  I tried a washing machine once, and to me it seemed to increase the breathing resistance until I washed it again in boiling water.  I’ve used one of these (not this one, but very similar design) to ride a bicycle 6 miles home from work, when we had the nasty smoke blow in from across the country.  I did not ride 100%, but I rode fast enough.  I also used a smaller one for a few hours on an airplane — it would not be adequate for exercise, but worked fine for sitting.

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No I didn’t write this because of the IPCC report, I don’t write that fast, been working on it for a while.

Something that has become more and more clear to me over the last few years is that there’s no single silver bullet for decreasing greenhouse gas emissions from transportation (aviation, shipping, rail, and particularly cars and trucks), which is now the largest US source of GHG emissions.  Partly this is because we’ve spent decades making ourselves dependent on fossil fuels, and partly this is because we can only change things so fast even if we want to.  And, because we’ve dithered for so long (with the obfuscating assistance of the fossil fuel industry and their useful political idiots), we don’t have much choice but to do everything we can, immediately, to cut emissions. If you think, “maybe GHGs are not a problem, I’m sure we’ll adapt”, this is not for you, stop reading, go away, you’re an idiot, no I will not approve your comments.  This is instead, do not be so focused on your own favorite silver bullet that you dismiss other things that would help, because anything that is roughly cost-effective would help, and we need all the help.

So, where are we now?  Right now, the median vehicle trip is only 5 miles (my calculation, from ORNL data), but that is only about the 30th percentile commute, which for a lot of people is a a 5-days-per-week round trip.  And short trips don’t cover a lot of miles; the average length of all trips (not just commutes) is 10 miles, but half the miles traveled occur in trips of up to 19 miles (this is not intuitive, I made a fake distribution in a spreadsheet so I could verify I had not made an error).  And the trips up to 5 miles only (cumulatively) account for about one-eighth of all miles traveled in cars and trucks.  So, bicycles and micromobility by themselves are not enough.  On the other hand, biking works for a whole lot of people, right now, all weather, e-bikes solve the hill problem and help with the range problem, and biking and micro-mobility could do a lot to improve use of long-haul transit, and reducing car use in dense places (cities) does a lot to make increased density not just palatable, but even attractive.

We’re producing electric cars, yes, but right now they’re only 2% of all new cars in the US (that’s new cars, not all cars), and the average car on the road is 12 years old; cars sold today will be with us for a while.  If we miraculously transformed all our cars to be electric overnight, we’d also need to make the electrical grid about 15% larger than it is now — not the GHG-free electrical supply, but the total supply, generated all ways, delaying the phase-out of existing dirty generation. The non-electric cars that we drive also tend to be ludicrously bloated; that’s no help at all.

We could move closer to our work and to shopping, but moving is a pain (says a friend, “three moves equals one fire”) and the first two decades of my life I lived someplace undergoing 3% population growth every year, largely in (literal) green-field development and it severely burdened the government to keep up (in particular, to keep up with school construction; “portables”, double sessions and 45-15 scheduling were all used to deal with the problem), so there are limits to how quickly people can move around and how fast we can build infrastructure to add people to an existing city or suburb, assuming that everything else aligns to make it possible.  On the other hand, we actually did this — 3% growth per year for 20 years, it happened, over a whole Florida county (Pinellas, decades ending 1970 and 1980, see also Pasco, and Hillsborough).

It’s also worth comparing the things we think are “hard”, with what’s truly hard.  Long-haul air travel without liquid fuels?  That’s really hard.  Ocean shipping at existing scale and speed without liquid fuels?  Also hard.  And among the liquid fuels, hydrocarbons are superior; alcohol could work, but it’s less energy per gallon or kilogram when burned, never mind that biofuel alcohol production has a lot of fossil fuel inputs (these could be improved, but that’s only at the experimental stage right now)  All the other substitute fuels have similar problems — burning hydrogen itself produces no long-lived greenhouse gases, but producing hydrogen requires energy, which comes from where?  And carbon capture?  Not proven at scale, and that also uses energy, who’s going to pay for that?  And where do we put it, to be sure it will stay put?  And yes we should keep studying these things, they look really interesting, some of them will turn into wins, but they haven’t yet, we need to diversify our risks, and we don’t have time to wait.

The distinction between what we can do now — things that are proven to scale, that are done elsewhere already, that were even done here in the past — versus things that we might be able to do in the future, is important, because we need to make real reductions now, not promised reductions in a future that will arrive as slowly as our dragging feet can manage.  The problem with global warming is that it does not reverse quickly; we’re emitting CO2 far faster than the climate can come into equilibrium (oceans absorb an almost incomprehensible amount of heat) and it persists in the atmosphere for hundreds of years.  If through some miracle we zeroed out our greenhouse gas emissions tomorrow, it would still take decades (centuries?) for the earth’s temperature and all its weird-weather effects to come into equilibrium; however, any reduction in emissions now is still good because otherwise the rate of change comes even faster and the endpoint is far worse.  

So, what have we got that we can do now?  And how do we help it happen?

Not driving

Not driving, how does that happen?  Buses, trains, subways, bicycles, scooters, skateboards and walking all worked well in the past, work in other places right now, and work for many people here already.  People use them in combination, i.e., “multimodal”. New technology, for better lighting, better tires, better batteries, better materials, and better motor controls has already made these better than they were in the past. There’s no particular reason to believe that not-driving should be rare.  

It’s probably worth describing some of the parameters of these other modes, because to read what other people say, it is clear that many people don’t know how they work.

(Begin digression)

On a plain bicycle, a typical speed is in the range of 12-15mph.  Some people can cruise at 20mph, but that’s not usual case.  Anyone cruising (not sprinting) at 25mph is in exceptionally good shape.  Only top athletes cruise at 30mph.  Increasing speed comes with sweat and safety tradeoffs; higher speeds generate passing conflicts with other riders, surprise drivers (if bikes and cars share space), and yield much more unpleasant crashes.  Someone who bikes 6 miles to work at 20mph will want a shower when they arrive; they’re typically drenched in sweat.  Cruising at 12mph means that 6 miles takes 30 minutes without stops, which is generally regarded as a comfortable limit on commute length and results in much less sweat, yet still provides plenty of exercise. For congested automobile traffic on surface streets, 12mph is quite competitive, given that a bicycle can filter up to intersections instead of waiting in line (multiple bicycles also clear intersections far more quickly than cars do per “lane”, even given the reduced size of a bicycle lane).  Solo crashes at lower speeds are also much safer.  Lower speeds are safer for pedestrians; though bicycles are far safer for pedestrians than cars are, pedestrians-fatality crashes at or below 15mph are even rarer.

E-bikes come in several flavors; throttle and pedal assist, and regulated at 20mph, regulated at 28mph, and (illegally) not regulated.  Typical e-bikes come with a 250W assist, which is “you’re now very fit” at the push of a button.  The legal limit in the US is 750W, which is quite a lot of power (more than the best athletes produce continuously) and there are bikes on the road with more than that; sometimes for speed, but the ones that I know of (I know of 2) use it for hill-climbing with cargo.  There’s wacky variation among state laws, but above describes California and federal regulations (which apply to use and sale, respectively).   20mph cuts a 6-mile commute to 18 minutes, and with much less sweat.  For my commute (through a Boston suburb and Cambridge) an e-bike would handily beat driving at rush hour, and would be competitive even off-peak, but commute speed is not my only priority (I also care about exercise, have repair skills that don’t include batteries and motors, and charging at work is a hassle).  One important thing that e-bikes do is flatten hills; it may be that the shortest route traverses a hill, or the safest route traverses a hill, and on a regular bike you might choose to avoid the hill because hills are work.  But on an e-bike, no problem.

The big win for multi-modal commutes (where the default multiple modes are “walking” and “transit”) is that the alternatives are notably faster than walking.  A 10 minute walk at 3mph is half a mile.  For a bicycle, assuming a minute spent locking up, the remaining 9 minute ride at 12mph is 1.8 miles.  For a train or subway station, that increased speed puts 13 times as much area within 10 minutes of the station, so crudely, 13 times as many people can reach the station without using a car, which would add to congestion near the station and also requires much more space for parking than a bicycle does.  A skateboard is slower (9 mph) but needs no locking if you carry it with you onto the train, so an extra minute, resulting in 9 times the area that can reach the station in 10 minutes.  A skateboard, if you are capable of using one (I’m not, at least not yet) is also supremely reliable; no pneumatic tires to puncture, no chain to come off, no brakes to fail.

For multi-modal commutes, plain bicycles are typically for first-mile(s) or last-mile(s); they’re good for either, but are more of a pain to take with you on a bus or train.  Buses often have racks on the front, but if lots of people were doing bike-bus-bike commutes (where the bike travels on the front of the bus), those racks would tend to be full and you might have to wait for a bus with an empty slot, which adds unreliability.  Some trains (Caltrain, e.g.) allow bicycles at rush hour, but when you compare the human occupancy of a “bike car” with a regular car, a rider + bike take 3 times as much space, and the increased difficulty of boarding and leaving the train carrying a bicycle risks increasing dwell times at stations. Level boarding platforms would help with this — roll on/off is much easier than carrying a bike up/down steps; this is an example of how doing “all the things” can interact favorably, because we should be doing level boarding for ADA and faster boarding in general.  Most trains and subways, however, do not allow plain bicycles at rush hour, because that would cut their overall capacity and they often run full (this is definitely true for BART and MBTA).  Folding bicycles typically receive an exception, but these are sort of an all-around compromise; the nicest ones are ok bikes, but not the best bikes, the lightest is 22lbs but over 30lbs is common, so they’re a noticeable hunk of “luggage”, and even folded they take up a bit of space.  E-bikes are useful for larger amounts of first/last miles, or those that include hills, but are much worse for bike-transit-bike unless the transit is roll-on and roll-off, because e-bikes are notably heavier than plain bicycles.

A skateboard tends slower than a bicycle, but is darn near optimal for multimodal use.  They’re light and compact, and you can carry them on a bus or train anytime, and typically use them right up to the moment you step onto the train/bus, crowds and local regulations permitting.  (Local regulations may not permit, because local regulators look down on the sort of riff-raff who would use a skateboard for transportation).

E-assist scooters, skateboards, mono wheels, and hoverboards are all very, very interesting. By default these can travel at least 20mph (unclear if they’re legally regulated or not) and are also relatively easy to carry on/off transit, depending somewhat on details.  E-skateboards are probably the easiest; hoverboards and mono wheels, in my limited experience (picking them up at a demo) are somewhat more lumpy, though more compact than a folding bicycle. Traveling at 18mph on something that you take with you on the bus or train means that the 10-minute area around a train station is now 36 times larger than what you could reach walking 3 mph.  Scooters require less skill, but are heavier (27lbs, versus 17 for an e-skateboard) and a little bulkier even when they fold, though the folding scooter I saw had a nice design for carrying.

For cargo delivery, especially urban cargo delivery, e-assist “bicycles” (actual bicycles, tricycles, and quadricycles) work well for small loads.  There are tradeoffs between loading time, time spent stuck in traffic, time spent traveling back and forth for new loads, and contention for loading dock space, which can be an issue for trucks, but much less so for bicycle delivery.

There are weather issues with all of these choices, but if the goal is not-driving, a fraction of the cost of a car can still buy both a bicycle AND an e-scooter, where the bike is better for cold weather (exertion makes heat, studded snow tires deal with ice and snow) and the e-scooter is better for heat and rain (less exertion; mostly stationary posture makes a rain poncho work better, less sweaty).

Trains and subways are notable because rail can carry a boggling quantity of people.  One subway line in Boston can carry (and does carry, at non-pandemic rush hour) as many people per hour in a single direction as 10 lanes of car traffic at maximum throughput. For longer-haul commuters, commuter rail carries 42% of the total rush hour traffic into Boston.

(End digression)

Quite a lot of what we need for other modes is attention paid to the same sort of convenience that causes us to default to cars today.  So, buses and trains, if they only come once an hour, that’s not convenient — so don’t do that, arrange for them to come more frequently.  Yes, that will cost money.  Waiting for transit, what if it is raining, what keeps the weather off?  So waiting areas should have a roof, and a bit of shelter from wind, too.  When it snows, we plow roads for cars, but we don’t plow sidewalks, and often road-plowing results in sidewalks being blocked at every street intersection; if we expect people to not-drive, better make it reliably physically possible.  Buses get delayed in traffic; when multiplied by all the people on the bus, that’s a huge inconvenience, so the bus should get its own lane and be able to trigger green lights at intersections. Biking, is there a safe place to lock-up a nice bicycle?

  • Build densely.  We did this in the past, we could do it again.  Not only does this shorten car trips, it also makes alternatives feasible.  But it seems unlikely that we could add density (people) faster than 3% per year.  The goal therefore should be to make whatever growth we can work as well as possible; site it close to transit stations, site it close to bike routes that connect to nearby destinations.  Don’t create dense housing in the middle of nowhere, even if that land is cheaper.  In some cases there are problems with municipal funding — it’s common to fund the  bulk of K-12 education from property taxes, so adding people puts pressure on a town’s budget — so fix those taxes, it’s not like that’s an inherently good way to pay for schools, it’s just a thing we happen to do (and it helps preserve the effects of redlining, so it’s kinda racist, too). There are other good reasons to make this funding change.
  • Make transit nicer (a non-comprehensive list of examples):
    1. Improve subway signaling so that trains can run closer together (this will save time and make them less crowded)
    2. Buses obtain a double benefit from bus lanes; not only is the bus ride less delayed, but the buses can run more frequently (or fewer buses can provide the same level of service).  For example, if a bus lane converts a circular 30 minute route into a 20 minute route, then it takes only 2 buses to come once every 10 minutes, instead of 3.
    3. At intersections, buses should be able to request an early green so that they are least-delayed, for the same reasons.
    4. There’s a level of crowding that causes many people to avoid transit; if there is crowding, great, transit is popular, but the goal is to get more people on it, not just minimize per-rider costs, so ADD MORE TRANSIT till the crowding is reduced.  If the existing service cannot be expanded (trains are maximum length, running at minimum interval, still crowded) then add alternatives — redundant bus and bike routes for short haul, better support for carpooling for long haul.
    5. Elevators should work, and should also be easy to find and access.
    6. Clean stairwells more aggressively (so that they don’t smell).
    7. Bus stops (and train stops!) should be sheltered from the weather.
    8. Trains should use level boarding, because that is faster, easier, better for disabled people, and eases the option of bikes on trains.
    9. Trains should use electrical power (not batteries, that is not yet proven for trains at scale) because that is quieter, cleaner, and provides faster acceleration from stops which saves time.
    10. Trains should come frequently, and where possible trains and buses should have properly synchronized transfers (frequent service takes a lot of the sting out of poorly coordinated transfers, but minutes spent waiting or walking add up fast).  We have a lot of rails in place already around some large cities, we just don’t use them enough.
    11. Transit should not shut down at midnight; there are people who need it at all hours.
    12. Transit stations should have abundant, safe, and convenient sheltered bicycle parking, and perhaps also lockers for scooters and skateboards; not everyone wants to carry those with them onto the train.
    13. Train tracks should be improved so that the ride is smooth, and people riding the train can easily read or work while they ride, if they wish to.
  • Make “micro mobility” nicer.  I have many, many suggestions here, because I ride a bicycle daily to work and am well aware of all the little friction points.  Someone with daily transit experience (I had that once…) can probably flesh out my suggestions above.  But on to the bicycles and little e-things:
    1. There really, truly, needs to be safer places to ride.  That probably won’t happen until a larger number of people are biking/etc, but if you want to get people out of cars, either driving has to become a lot less pleasant (that will be ever so popular) or else not-driving has to become a lot more pleasant.  And this right here is the number one item.  Safe, separated, relatively direct and non-squirrelly bicycle routes connecting popular places.  And allow all the little e-things to use them, too — seems obvious, but some places (e.g., Massachusetts) have laws that technically ban e-assist from bike paths.
    2. Uniform sensible standards for all the e-things, so the markets are bigger.  That means, the same power limits and speed limits and where-you-can-ride and who-can-ride and what-you-must-wear rules in all the states must match.  California has good-enough rules, every state should adopt California’s standards, no, your state is not special.  Your safety objections are foolish, if you cared about safety, you’d be all over item #1, #3, #4, and #5, your state is not special, your city is not special (yes the European speed limit is better, but 20mph is not terrible).
    3. Trucks should have side guards.  This is the rule for some US municipal truck fleets, and is the rule in much of Europe.  Sideguards reduce bicycle (and pedestrian) overruns, which are deadly and horrible.
    4. Trucks (large and small, including pickup trucks) should be designed for improved visibility.  It’s been done in Europe, we could do it here.  
    5. Curbs should be rounded over.  Sharp-edged granite curbs are a gratuitous hazard in any crash (they’re also heck on car tires).  Either the sharp edge can be rounded off, or the granite can be replaced with concrete, which works fine with snowplows in Minneapolis and Chicago (you can look at curbs on Google Streetview, and I wrote to both highway departments to ask about durability and cost and they said it is fine).
    6. One-way streets by default should include a counterflow option for bicycles/etc.  Streets are often made 1-way to prevent car and truck cut-throughs in quiet neighborhoods, but bicycles and other small things are quiet and safe so need not be excluded, and benefit themselves from the safe, quiet cut-through.
    7. Bicycle parking should be abundant, easy to find, easy to use, and should include provision for oddly-shaped bicycles (tricycles, for people who lack balance; cargo bikes, for people who need to transport children and other cargo; recumbents, for people with back issues).  Some bikes are heavier than their riders can lift into upper racks; some bicycles have wide tires.  Some popular rack designs are actually terrible; those should be avoided.
    8. Bicycle parking should be sheltered from the weather, and where theft is a problem, should include anti-theft measures. For example, at the MBTA Pedal&Park bicycle parking, access requires a registered commuter card, the cages are monitored with video cameras, they are sited so that anyone walking by can see inside, and there’s a cardboard policeman at the end because studies show that helps a little (and the cost is low).
    9. At intersections, “Idaho Stop” should be the rule for bikes etc.  This is “treat stop lights like stop signs, treat stop signs like yield signs, and of course that always includes yielding to pedestrians”.
    10. At intersections, bikes etc should be allowed to proceed on the LPI (early walk signal) and on all-ways pedestrian signals, again yielding to pedestrians.
    11. Lights along bicycle commute arteries should be synchronized to bicycle speeds, not car speeds.  This will save time and also reduce sprinting at yellow lights, which is not the safest thing for either cyclists or pedestrians.
    12. Bike/etc lanes and paths should be smooth.  That means preparing off-road paths well enough that tree roots don’t tear them up in a few short years, that means any piece of a road re-designated for bicycle/etc use should have its pavement checked and fixed (the default is that it is awful).
    13. Bike/etc paths and lanes (especially the lanes) should be clean and (especially) clear of glass and other tire-damaging debris.
    14. At minimum lanes should wide enough for people to comfortably ride side-by-side.  Off peak, people often like to ride together, at rush hour people need to pass, and some bikes are wider than others.
    15. Adopt German lighting rules; requiring and standardizing lights means that they’re cheaper, ubiquitous, and annoy pedestrians and other cyclists much, much less.
  • Make “walking” nicer.  Here, walking also includes rolling, in wheelchairs and mobility scooters. And, again, my knowledge here is incomplete, this is just a start.
    1. Streets and roads should have sidewalks, and those sidewalks should be comfortably separated from the road.
    2. Roads should have crosswalks at useful intervals.  Pedestrian overpasses are not preferred because climbing stairs is work and anti-wheeled-thing and climbing ramps tends to add distance, and adding distance for the slowest mode is bad.
    3. Intersections should be designed to enhance pedestrian throughput and safety.  For example, right-turn-on-red should not be allowed any place with much pedestrian traffic (or near parks and schools where children are likely to be using the road).  Slip lanes should be avoided because they encourage hasty turns.
    4. In urban areas with lots of pedestrian traffic, sidewalks should be adequately wide for that traffic.
    5. Sidewalks should not be the default repository for random clutter and road signs; there should be a clear and unobstructed path.
    6. Where it snows, sidewalks should be plowed first.  Crosswalks should not be obstructed by snow piles.
    7. Adjacent roads should be puddle-free so that pedestrians do not get sprayed when it rains; or, there should be barriers to prevent this (a bike lane protected by parked cars is an adequate barrier; or, a wide bike lane).
    8. Urban sidewalks should have awnings so that people on foot are shielded from the worst of the weather.
    9. Crosswalks must drain properly, so that people walking step in many fewer puddles (and would you want to handle a wheelchair wheel after it had been dunked in who-knows-what?)
    10. Trucks should have many fewer blind spots, and the high front grills that are popular now in the US have practically nothing to do with actual truck utility, and should be banned.  There’s no need to design new trucks, because these regulations exist in other parts of the world (e.g., Europe) and their designs could be used here instead.
    11. Laws against jaywalking should be revised.  Some other countries do have similar laws, but they’re weaker (typically applying only “within 50m of a crosswalk/intersection”) and our laws haven’t resulted in greater pedestrian safety.  In practice their main use is to give cops an excuse to harass black people.

If we can’t stop driving, we can still drive smaller cars less, and maybe make them electric.

Not driving is an effective way of reducing GHG emissions from driving, but right this moment, many commutes are impractically long, shortening those commutes takes time and money, useful transit doesn’t reach all people, and there’s no replacement ready for those disabled people who get around in cars now (there should be, but we haven’t gotten around to designing it, so instead, they get cars).  So, given that some of us are really stuck using cars, people need to change how they use them to reduce their impact (and they’ll need to keep doing this for decades, until their car is electric and the electrical grid is mostly fossil-fuel-free):

  • Reduce car trips.
    • car pool.  People did this in the past, people still do it today to help take advantage of HOV lanes.  There are places, now, where people do “casual carpooling” (aka “slugging”) for this.  The win is larger for longer trips because it’s easier to amortize the time to gather passengers, and long trips account for many miles.  This seems like something where an “app” should help; not one done for profit by windfall-seeking tech, but by (contracted by) a transit system.
    • use (grocery) delivery services, carefully.  Don’t use one that just replaces point-to-point car trips with someone else’s, and don’t replace a single trip per week with many smaller ones.  Do use those that bundle several deliveries into a single trip, or do use those that don’t use a car (especially, not a hydrocarbon-fueled car).
    • combine trips (e.g., buy groceries on the way home from work).  Maybe you think you’re already doing this, but if we can do more, we should.
    • don’t drive the short trips; people may not be car-free, but perhaps they can find an alternative for the trips that are short.
  • Shorten car trips.
    • live closer to work.  This is hard, partly because we have social (tax) policies designed to encourage home purchase instead of home rental, and that makes it harder to move.  This is also hard because typical zoning restricts density, which limits the amount of housing that is actually near work. But if the need or opportunity to move appears, favor a shorter commute — 20 miles is 33% less than 30 miles, that’s a savings.
    • use zoning to cluster “work” locations closer to where people already live rather than out in the boonies, so that transit and carpooling are more likely to be effective, and also so that a change in jobs is less likely to result in a huge change in commute.
  • Don’t drive fast.  For energy conservation purposes, this is more about highway speeds, though there are also important safety reasons for not driving “fast” around pedestrians.
  • Use electric cars.  Even with our still-plenty-of-fossil-fuel electrical supply, electric cars are more efficient, overall this is still a win.  But at our current rate of not-e-car replacement, this will take decades.  Nonetheless, for a long commute, try to buy an electric car sooner, not later.  Yes they are expensive.
  • Use smaller cars.  For gasoline-powered cars, obviously, smaller cars get better mileage, better mileage means reduced emissions.  But if it is an electric car, smaller cars have smaller motors and smaller batteries; actually scaling up the electric car fleet will bump into various production constraints (Lithium? Copper?), and the smaller electric cars are, the more we can build before those limits hit.  Note that these are rate-of-production constraints, not resource limits; in the same way that we can only move so many people into a city per year, we can only grow production so fast.  When we hit (temporary) limits, we’ll get price spikes, better to stretch our production capacity into the largest number of cars instead of into the largest cars.
  • Politically, stop inconveniencing other modes.  For example, stop defending street parking from replacement with bike lanes or bus lanes, and stop opposing street designs that prioritize pedestrians.  Don’t oppose camera enforcement of speed limits near schools or in urban areas.  All the other modes must become nicer and safer if we expect people to use those instead of driving; the alternatives to carrots for other modes, is sticks for driving.

These are things to do, permanently, until the electrical supply is green enough and all the cars and trucks are electric.  And yes, this will involve some tradeoffs, some of them unpleasant, but for cars and trucks, our progress in reducing GHG emissions thus far is terrible.  We’ve made a bunch of dumb choices in the recent decades, those choices will cost us now.  We embiggened our cars and trucks unnecessarily, we made rules against building housing close to where many people work.  We decided that the highest use of a good fraction of our urban streets was car storage.  These were mistakes, and now we have to reverse them as fast as we practically can.

And yes, I really think we have to do all this stuff, and quickly.  Not just “we have a schedule” or “we’re waiting on proposals from a task force”.  Do them.  Now.  Sooner really is better.  If it requires new laws, pass the laws.

I have no idea if my comments are any good or actually help, but I figured I would try.  I hope, a little, to get a toe-hold in their allegedly metrics-driven brains.


I read all the comments from Toole Design (FHWA-2020-0001-0853, tracking number kn4-yvok-yobh), and agree with them entirely.

A few that I thought were especially on point included:

Placement of crossing signals; these must be accessible from a wheelchair even after typical snow plowing. See attached picture for a bad example (this is a button-requested-signaled-crosswalk across Fresh Pond Parkway in Cambridge, MA). For that particular button, it is also quite close to a road full of sometimes-fast traffic, which can be nervous-making to drivers if a cyclist approaches quickly, and nervous-making to parents with children who wish to cross.

IMG 20190121 182309

Counterflow bicycle lanes; I agree entirely, these should not be unnecessarily restricted. There are some that I use every day on low-traffic roads that are not parking protected, and they are completely fine. If it were up to me, every single road that was “one-way” for the purpose of thwarting cut-through automobile traffic would be two-way for bicycles because of their reduced noise, pollution, and danger to other road users.

I agree with their remarks about way-finding signs. Times are appropriate; in particular, fast riders not only know that they are fast riders, they know how much faster than usual they are, and can deal with estimates for the “average” or “median” bicycling time. (I default to 15% faster than the Google Maps bicycle estimates; this is a thing I know. I can shave off another 15% if I try very hard.)

In urban areas (my commute crosses Cambridge, MA, errands often take me into Somerville) the 85th percentile rule is completely inappropriate. The most basic flaw is that it assumes that which does not exist, “free flowing traffic”. Actual rush hour traffic speeds are roughly the same as the median bicycle speed, or slower.

Furthermore, in the previous year (2020), we conducted a natural experiment on all types of roads to see what would happen to crash rates when we remove cars from the road, allowing traffic to flow more freely at the speeds more often chosen by drivers. The outcome was not favorable; in Massachusetts, the number of fatalities did not fall in proportion to the reduction in traffic (see https://www.bostonglobe.com/2021/02/08/metro/driving-decreased-mass-last-year-not-traffic-deaths/ ). This strongly suggests that prioritizing driver speed will reduce safety, and that the “free flowing” part of the 85th percentile rule is especially suspect.

Regarding urban areas again, whenever there is any consideration for “traffic flow”, it must include all road users (pedestrians, cyclists, drivers, scooters, skateboarders — I see all of these in Cambridge) and mass transit users must be weighted individually; i.e., it is not “one bus” but rather “50 passengers”. This is a bare minimum; there are issues of equity and access that I am not really qualified to comment on but I know they exist. There are roads in Cambridge where the bus traffic at rush hour, counting people, exceeds the car traffic (Mt. Auburn Street). This was used to justify a restricted lane for buses, which improved bus speeds and (I heard, and it would be expected for improved bus service) led to an even larger number of people using the bus. There are intersections (Inman Square) where the summer rush hour bicycle traffic is 30+% of the total (this was estimated by counting cars and counting bicycles; for a 45-second green, that’s about 22 cars, and 11 bikes means 33%; this is relatively common at summer rush, and I’ve seen as many as 20 — and it’s not that welcoming an intersection.) Winter traffic is lower, but this is a case where lack of safety (inadequate separation from traffic; lanes narrowed by snow piles) causes a mode shift; walking or waiting at a bus stop are both actually colder than riding a bicycle (source; my daily bicycle commute, and getting uncomfortably chilled walking to lunch when I forget to bring a jacket for walking. I have been doing this for years, and have had the experience multiple times.)