Bike Lanes are Good Except They’re Not Except They Are

One of the cycling community’s most visible successes in recent years is the inclusion of bike lanes in all new arterial streets throughout the Valley. Because of the bike lane, if I have to choose between taking Union Hills and Bell, I take Union Hills every time. At the same time, I’d much rather ride on Fillmore than Union Hills and there aren’t any bike lanes downtown. The difference isn’t that there are or aren’t bike lanes, and it’s only minimally about the traffic volumes. It’s about the speed.

Major arterials in Phoenix have design speeds of 55 or 60 MPH. The FHWA gives a range of design speed for urban arterials at 30-60 MPH. Phoenix’s Street Planning and Design Guidelines illustrate that the six-lane major arterials (Design A and Design B) have a 60 MPH design speed. Considering design speed is much more relevant to any conversation than speed limit because people prove daily that they’ll drive how fast they feel comfortable driving. I consider myself a pretty strong cyclist, part of the “Strong and Fearless” group anyway, and I can travel pretty comfortably between 20 and 25 mph on flat ground. If I’m going 20 MPH and a vehicle is going 60 MPH, that’s a 40 MPH difference. What that mostly means to me is that if a motor vehicle is 500 feet behind me, the driver has roughly 8.5 seconds to see and respond to me, at which point I would be passed at about a 3-5 foot distance by a piece of metal traveling 40 MPH faster than me. I know we’ve all seen this chart already, but there’s a reason it’s used so much (Source: NHSTA Literature Review on Vehicle Travel Speeds and Pedestrian Injuries, Figure 1):


At a 40 MPH difference in speed between a pedestrian and a motor vehicle, the odds of receiving an incapacitating injury or being killed stands at 62.6%*. While relatively few collisions occur simply by a driver hitting a cyclist from behind, the implicit threat of catastrophic injury due to the high-speed difference deters many casual riders from taking that chance. Remember: this is the speed difference between design speed and a fast cyclist. Someone on a beach cruiser going 10 MPH has less than seven seconds of exposure to the motorist from 500 feet, and the 50 MPH speed difference increases the percentage of crashes resulting in death from 22% to 36%**.

Staying with that chart, the chance of incapacitating injury of a pedestrian hit by a motor vehicle increases most significantly between the <20 MPH range (20.5%) to the 21-25 MPH range (35.7%) while the risk of death approximately doubles with each 5 MPH of speed difference. Most casual bicyclists don’t know the statistics, but they intrinsically know that being too close to cars going too much faster than them is dangerous, and the greater the speed difference the more dangerous it is.

The great debate on whether a bike lane is actually safe, however, typically lies in the turning movements. Do bike lanes “hide” you from cars making turning movements; do they give the cyclist a false sense of safety so they let their guard down? In writing up this post I wasn’t able to find any research that would confirm or deny those arguments***, but from my own experience: it doesn’t matter. The two most dangerous movements I face every day are when I approach a car who suddenly turns right without a signal and being in the blind spot of the last car through an intersection when a vehicle traveling the opposite direction is turning left. I don’t have too many motorists pass me then suddenly turn right in front of me and cut me off, though that may be a bigger worry in an urban environment like Downtown Seattle where there is much more stimuli for a motorist to be aware of****. Sharing a 10-foot road would preclude the motorist being able to pass and subsequently cut a cyclist off, but a 14-foot road would allow the exact same movement with or without a marked bike lane. The left hook would be a worry in most instances regardless of road position except when cycling in the most left portion of the lane, something that is discouraged and probably could be argued to be in violation of the “as far right as practicable” verbiage in state law.

Ultimately, bike lanes do appear to encourage more cyclists (good), less sidewalk cycling (good), a defined space and predictable movements from cyclists (good). But they clearly have limitations on how much they help. I will advocate consistently and vociferously that there is no place for a 45 MPH speed limit / 60 MPH designed roadway in our cities. But, expecting that even the most progressive city won’t eliminate all these urban highways in my lifetime, identifying appropriate facilities for each road design would be a compromise worth discussing. Segregated bicycle facilities are at work in Chicago and DC and have been in play across the pond for decades, so we have best practices to guide us how to disallow motorists from making right turns on red lights, giving cyclists and pedestrians a jump start from a signal queue, or even their own dedicated signal to create a “green wave” for cyclists. Completely segregated facilities should be available on major arterials with design speeds at or above 45 MPH. Wider bike lanes, or a set of pavers separating cyclists from motor vehicle traffic would keep cyclists close enough to the roadway for motorists to see, a physical barrier to separate modes, and the space to reduce the physiological response you get from nearly getting hit are necessary for streets with a design speed between 35 and 45 MPH. From a comfort standpoint, standard bike lanes as we know them should be most prevalent on roadways with design speeds between 25 and 35 MPH. These are speeds at which motorists have an adequate amount of time to observe and respond to a cyclist, and motorists are moving slow enough to effectively reduce the fear factor for most cyclists. At or below 25 MPH it is not unreasonable to expect both types of vehicle to interact positively with one another with gentle reminders that all users are entitled to the roadway by using sharrows or signage.

With so much of our public budgets being poured into transportation and roadways, there is an argument to be made that cyclists (and by extension, pedestrians) should have the same equity in the public right of way. I’m not arguing for a monetary equivalent (can you imagine how many full-on cycle tracks we could build for the same $1.2 billion South Mountain Freeway budget?), but an access equivalent. With so much effort and time spent to reduce the number of motor vehicle collisions through segregation (medians, signals, additional lanes), why are cyclists left to be protected by three inches of white paint on the ground?

*For my argument, I’m choosing to use difference in speed rather than absolute speed because the difference in speed is the relative impact your body would feel if it were hit by a car; it doesn’t take into account the greater stopping distance by the vehicle if you’re trapped underneath or the velocity in which a cyclist would hit the ground or a fixed object as a result of the initial collision. I consider these events to be circumstantial and event specific.

**Of the cyclist; there aren’t too many deaths by people in cars when they hit a bike

***Lots of conflicting anecdotal internet pieces. Robert Hurst’s The Cyclist’s Manifesto really doesn’t care much for bike lanes, but it also largely ignores the young or especially vulnerable cyclist, and [I’m paraphrasing here] tells able-bodied would-be cyclists to suck it up and get over their fear. He may be right, but psychologically many people just don’t work that way.

****My own Seattle cycling experience is limited to the Burke-Gilman Trail (quite possibly America’s premier multi-use trail) and some smaller neighborhood streets through the U-District and Kirkland.

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