Bicycle lights

Happy Friday, everybody!

It seems like a lot of people are thinking of bike lights recently.

There are these cool active lightning bicycle tires. In Kansas City, local cycling advocates are handing out free bike lights. And the Chicago Department of Transportation created this bike lighting video as part of their series of bike safety videos (Via Chicago Bike Advocate):

Bikes For the Rest of Us “Bright Lights for the Rest of Us” repeats the claim that “taillights are even more essential than headlights.” This is an expression of the natural but irrational fear many of us have of getting hit from behind.

When bike light maker Light & Motion did market research last year for new and improved bike lights, they found 96% of surveyed cyclists fear the rear more than anything else.

96% of cyclists fear the rear
Graphic courtesy of Light & Motion.

70% of bicycle crashes are from the front. If I had to choose between front and back lights, I’d pick the front.

Think about this: a motorist approaching from behind has his headlights shining directly at you. Unless you’re a complete bike ninja with black clothes on a black bike and a black backpack, the motorist at least has a chance of seeing you. He has headlights to ensure he doesn’t run over stationary hazards on the road, so hopefully he’ll see moving objects as well. Even cars with broken taillights aren’t invisible to following traffic.

A motorist going through intersection, though, won’t see the cyclist approaching from the left or right on the cross street. The cyclist is coming from the side, exactly where the headlights are not shining.

This is probably the reasoning behind many state bike equipment laws in which headlights are required, but only a reflectors are mandated for the rear.

I’m counting angels on a pinhead here, of course. Realistically, cyclists should have front and tail lights, and I recommend side lighting as well. I like to go bright on the front, but I don’t sweat things too much on the taillight unless I plan on hitting high speed expressways or ride in poor weather. As long as I have reasonably fresh batteries and the light is aimed correctly, I’m good to go.


  1. All the data on bicycle-car collisions shows rear-end collisions are more common than head-on. Regardless, the most telling thing about the Light and Motion chart is the percentage of accidents occurring after 4 pm.

    BTW, I'd go w/ NHTSA data over market surveys. The one you refer to was probably conducted by the Leisure Trends Group – not by any means a safety organization.

  2. @Freewheel: I think you meant “head-on are more common than rear-end.” NHTSA doesn't generally track cyclist perceptions, and NHTSA accident stats data doesn't show collision “types” — for the graphic, this came from New York City traffic accident stats as well as meta data from the National Highway Institute. Stats from states and localities that also track bike collisions by “type” back up what the graphic from L&M shows. See, for example, Fort Collins Colorado analysis of crash data showing 8.5% of bike vs car are hit from behind. It's notable to mention that almost all fatalities are from hit by behind, but in Ft Collins, hit-from-behind is likely on a rural road at high speed. Like I mention in my post, you certainly should be well lit at the rear on those types of situations.

    The market survey data only shows customer perception, i.e. the 96% who fear the rear. This was from on-street survey of cyclists in downtown San Francisco and “core commuter markets” in Pacific Northwest and DC area.

  3. …and it's perhaps notable that L&M decided to address the market's perception of fear from the rear by creating very bright tail lights, but they also address the reality of from-the-side collisions by designing some decent side lighting into their bike lights.

  4. Jeez… cyclists should trust their instincts and I wouldn't belittle them or call them irrational or suggest that unless they're dressed in all-black like a ninja, all will be well.

    Most rear-end collisions occur at night, which is what my post is talking about. If rear-end collisions make up a smaller portion of the overall “collisions” pie, that would be because 97% or more of bicycle trips are made in broad daylight! If you want to read about some real-life tragedies, google “fatal rear-end cyclist collisions.” My post discusses a recent fatal rear-end collision that occurred in the D.C. area. Trust your instincts – use taillights!

  5. @Freewheel: There's honestly no belittling in calling all of us “irrational,” but I think it's important for us to recognize our irrationality. We're human. We're all — and I include myself in “all” — naturally jumpy with large loud objects approaching us from behind. These behaviors are built into us, but it doesn't mean our responses to threats are always rational. Read Bruce Schneier's “Beyond Fear,” Tom Vanderbilt's “Traffic,” or Dan Simon's “Invisible Gorilla.”

    And yes, I agree we should have tail lights, but I already mentioned that in the post.

  6. I'd rather have a taillight than a headlight, if I had to pick just one. The fear of getting hit from the rear doesn't come from just not being able to see a car come up behind you, but it's also because you're so close to the cars that are passing. If someone on the other side of the road, 30ft away, doesn't see me, there's less of a chance of them swerving into me as they reach for their cellphone or radio. Plus, since I can see them, I can judge what I want to do next according to what I see them doing.

  7. There's something to the concept of a very good front light providing visibility for drivers approaching from the rear. If the front light has significant “side spill” lighting up not just the road but surrounding objects in front and front/sides of the rider, it creates a pool of light that is visible at significant distance from all sides. From the rear, the rider will create a silhouette in that pool. I notice when I'm driving that often I'll see that pool in the distance before I'll notice the tail lights of a car – especially in dark areas.

    That being said, I have a ripping good tail light, too!

  8. The often cited major US study is Bicycle and Pedestrian Crash Types of the Early 1990's (FHWA-RD-95-163, all 9 MB of it available online at…). Of their 85 crash types, 5 (6 including “Type unknown”) are in the “Class D: Motorist overtaking bicyclist”. They compared their data to the 1977 Cross and Fisher study and for this class of crashes:

    1977 study, Total Fatal=166 of which 37.8% were motorist overtaking, Total Nonfatal=753 of which 10.5% were overtaking
    1990's study, Total Fatal=41 of which 29.3% were motorist overtaking, Total Nonfatal=2453 of which 9.8% were overtaking.
    Note that there is not statistically significant decrease in the proportion of fatal or nonfatal overtaking crashes from the 1977 study to the 1990's study. Also note this is a bad type of crash, e.g. 9.8% of crashes but 29.3% of fatalities.

    For more recent data, you can do your own quires of the online database of the North Carolina Dept of Transportation, Division of Bicycle and Pedestrian Transportation at The fraction of motorist overtaking crashes in this database increases over time in both rural and urban settings. In 2007 (latest data in the database) motorist overtaking crashes accounted for about 30% of rural crashes and 10% of urban crashes.

    Such crash compilations are helpful in knowing what type of crash to watch out for under what conditions (e.g. urban vs rural, day vs night, intersection vs no intersection etc.)

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