Cyclists are notorious for running stop signs and there’s probably nothing else we do that raises as much ire among motorists and provides as much fuel for the anti-bike contingent. It can be extremely dangerous, and it undoubtedly breeds an environment of mistrust between motorists and cyclists. Given the fact that most cyclists are law abiding citizens in every other regard, why do so many choose to roll through stop signs and red lights (myself included)?
Joel Fajans (bicycle commuter and physics professor at UC Berkeley) and Melanie Curry (bicycle commuter and managing editor of ACCESS Magazine) think they know why. In their essay Why Bicyclists Hate Stop Signs, they point to the excess energy required to make frequent stops and starts as the culprit:
With only 100 watts’ worth (compared to 100,000 watts generated by a 150-horsepower car engine), bicyclists must husband their power. Accelerating from stops is strenuous, particularly since most cyclists feel a compulsion to regain their former speed quickly. They also have to pedal hard to get the bike moving forward fast enough to avoid falling down while rapidly upshifting to get back up to speed.
For example, on a street with a stop sign every 300 feet, calculations predict that the average speed of a 150-pound rider putting out 100 watts of power will diminish by about forty percent. If the bicyclist wants to maintain her average speed of 12.5 mph while still coming to a complete stop at each sign, she has to increase her output power to almost 500 watts. This is well beyond the ability of all but the most fit cyclists.
Fajans and Curry put their theory to the test on California Street in Berkeley, one of the city’s designated “bicycle boulevards” that has 21 stop signs (!) over a 2.25 mile stretch. By comparing California Street with nearby Sacramento Street—which has few stop signs—they were able to measure a 30-39% difference in average speed due to the required frequent stopping and starting on California Street:
One of us (Joel Fajans) found that keeping exertion constant, he could ride on Sacramento at an average speed of 14.2 miles per hour without straining. At the same level of exertion, his speed fell to 10.9 mph on California if he stopped completely at every sign. Thus Sacramento was about 30 percent faster than California. By increasing his exertion to a fairly high level, his average speeds increased to 19 mph on Sacramento and 13.7 mph on California, so Sacramento was then 39 percent faster. While a drop of a few miles per hour may not seem like much to a car driver, think of it this way: the equivalent in a car would be a drop from 60 to 45 mph. Because the extra effort required on California is so frustrating, both physically and psychologically, many cyclists prefer Sacramento to California, despite safety concerns. They ride California, the official bike route, only when traffic on Sacramento gets too scary.
I observed this exact thing when I was in Berkeley last year. During the rush hour commute, I counted far more bicycles on the busier, more dangerous thoroughfares than on the designated bicycle boulevards. I can only imagine it’s because of the large number of stop signs on the quieter BBs.
Fajans and Curry suggest that the issue is mostly a result of car-centric traffic planners not truly understanding the needs of cyclists:
Car drivers say they are confused by the presence of bicycles on the road, and some wish the two-wheelers would just go away. Bicyclists know that cars cause most of their safety concerns . Traffic planners need to find ways to help bikes and cars coexist safely. A good place to begin is by taking the special concerns of bicyclists seriously, and not assuming that they will be served by a system designed for cars. Reducing the number of stop signs on designated bike routes would make bicycle commuting considerably more attractive to potential and current riders. Allowing bicyclists to treat stop signs as yield signs, as some states do, could solve the problems in a different way.
Perhaps cities should buy bikes for their traffic engineers and require that they ride them to work periodically. There ’s probably no better way for them to learn what it’s like to ride a bike in traffic than actually to experience its joys and hazards.
I have to agree with the authors; their call for more sophisticated traffic planning, that takes into account the true issues cyclists face on the road, is right on the money.
Read the full article (PDF) →