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

June 26, 2022

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.

One Response to “How to bike in Cambridge and Somerville (and perhaps other places)”

  1. Mike Kupfer Says:

    This is a good set of recommendations for biking *anywhere*.


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