Bicycle Conspicuity in Low Light

There are several common crash scenarios involving bikes and motor vehicles.  In this article we will discuss rear-end crashes where a motor vehicle collides with the rear of a cyclist.

Generally speaking motor vehicles are traveling faster than bicycles.  As a faster-moving vehicle approaches and begins to overtake a slower vehicle it is the responsibility of the faster driver to go around the slower vehicle in a reasonably safe manner.  This seems to be common sense, and sounds easy to accomplish...provided that the driver even knows that there is a bike ahead, and how close the bike is to their car.

The majority of the information that we as drivers take in about the road ahead and how to navigate the hazards ahead is visual information.  As we approach something from behind we first need to: 1) realize that something is there, 2) figure out what it is and if its path is in conflict with our path, 3) come up with a plan for how to interact with whatever it is, and 4) start to do whatever our avoidance plan is.  We sometimes call this "perception/reaction."  And, while all this is happening we are still traveling closer to the thing ahead of us.

The first two components, being able to recognize that something is even out there in front of us, and figuring out what it is and if it is a threat to us, are critical for the rest of the perception/reaction process to occur with a positive outcome.

For us to appreciate that something is there it needs to contrast from its surroundings.  In bright daylight we can use color and texture to help distinguish an object ahead from its background.

In low light or dark conditions when texture and color do not visually work well we rely on motion and lighting to capture our attention, and to make an object ahead stand out from its background.  The nice fluorescent lime green cycling jersey that stands out from the grey roadway at noon on a sunny day is useless at night when our color vision is reduced.

So, cyclists add lights to the rear of their bikes to stand out.  Makes sense...or does it?  When a driver sees a small red light ahead they go into their database of images they have acquired in their driving experience, (when we drive and we look out ahead we are "pattern matching" for things or situations that may be a threat) and they come up with a perfect match: it is a pair of tail lamps on a car that is a long ways up ahead.  After all, when we view tail lamps from a distance they appear close together, and almost as one single light.

The apparent car that is a long way ahead is not a threat.  After all, the driver has been behind about a million cars before.  No big deal until the lights spread wider apart as this would signal that the driver is getting closer to the car ahead.

And about 1/2 second later the driver hits the cyclist from behind.  The driver will report to the police that they never saw the cyclist.  They may even tell the police that the cyclist didn't have any lights on the back of their bike.

The problem in this crash case was one of the cyclist's conspicuity.  Yes, they did add a red light to the rear of their bike.  But, the solid red light actually lured the approaching driver into a false belief, and caused the crash.  In the transportation world we say that the cyclist "violated the driver's expectations."  And, the driver is usually incorrectly blamed.

Let's look at the next level of lighting that a cyclist may add to their bike - a flashing red light.  What does a small flashing red light near the right side of the road look like to an approaching driver?  It looks like a car way ahead with its right turn signal flashing.  By this point I think that you know how this will turn out.

So how does a cyclist make themselves stand out from the normal visual landscape of the roadway ahead?  A recent and inexpensive lighting solution does exist: a random flashing bright red light.

Several manufacturers now make inexpensive red bike tail lamps that have random flashing patterns.  There are no normally-appearing random flashing pattern lights on the rear of motor vehicles.  This makes the random strobe pattern of the bike light stand out from its background and be conspicuous.

Granted, the approaching driver may not know exactly what is ahead, but they should realize that it is not something normal, and they need to move over to the left a bit.  And, in the end, that is usually the one single driver action that is needed to avoid a crash. 
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