Ask R. Moses: When are bike lanes helpful and when are they not?

Today's Question:

My friend lives on a street in a new neighborhood that is under development. The street is wide, solely residential, has sidewalks and a 25 mph speed limit. All new streets that are more like through streets in our area are built with bike lanes. My friend thinks her street should be painted with bike lanes. I think that the street has plenty of room for bikes, and that, given the low speed and low traffic, bike lanes aren’t needed. Is it better to paint bike lanes if there’s room in all cases?
— Bike Curious

R. Moses' Answer:

You describe the street as “wide.” How wide are we talking here? If the street is wide enough to induce high traffic speeds that would endanger bicyclists, my first recommendation would be: build it narrower. Barring that though, here are a couple of options that could increase the safety of an overly wide residential street—for people on bikes and everyone else:

  1. Paint bike lanes. Yes, it might be the right choice. It can help visually narrow the travel lanes, which may in turn help to reduce speeds. It also sends a reminder to drivers to expect other uses on the street. This is not the best response, but may be better than nothing. 
  2. Encourage on-street parking. Many residents on streets where cars go too fast will purposefully park on the street as a very effective way to narrow the available pavement for vehicle traffic, which typically slows things down a bit. This may not be compatible with bike lanes, as the parked cars might either block the bike lane, or create a hazard when car doors open into the bike lane (though this would probably be pretty rare on a low volume residential street). It is hard to know without any dimensions. If there are any parking restrictions on these streets, they should be eliminated (except of course where necessary, i.e. near hydrants). 
  3. Do some traffic calming. Putting in design interventions like mid-block chokers or curb extensions can beautify the street while making it safer. Perhaps these could be incorporated into the design of these new streets, or at least the ones that are not yet built. Here are some resources to help you get started with traffic calming.

If, on the other hand, the street is not wide enough to invite speeding cars in the first place, I would say your inclination to avoid painting bike lanes is spot on.

I’ll refer you back to my response to a question from last year on center lane striping. In it, I discussed the way that striping—whatever form it takes—denotes “my” territory from “your” territory. Unstriped areas like quiet residential streets are generally understood to be common spaces while striped areas can invite more aggressive driving and a sense of entitlement about who is allowed in what area. This can go both ways when we’re talking about bike lanes: it means that bikers have a space designated as theirs that drivers should (theoretically) not enter. But it also means that drivers have a space denoted as theirs, which may induce them to drive more quickly and disregard the other users around them.

In conclusion, if this wide street is likely to induce speeding, then some traffic calming efforts—which may include bike lanes—would help, like your friend suggested. If, on the other hand you can ensure that the street only invites slow traffic, then striping in unnecessary and could even be harmful.

How would you respond to this question? Jump in with your answers in the comments.

Note: R. Moses is not meant to be professional engineering advice nor should be relied upon as such. Consult your own technical professional before proceeding with your own project. 


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