Is a Rear Light Enough?

Here in Vancouver I frequently see cyclists riding after dark. Of these, far too many have no lights on their bikes, while of those who do have some form of lighting, the absence of a front light is very common. For those who choose to use only a rear light, two explanations come to mind: easy hardware and perceived safety.

First, easy hardware. The flashing red LED lights favoured in North America are widely available, inexpensive, easy to use, require only two AA batteries, and run for a remarkably long time on a single pair.

Second, perceived safety. It seems that many cyclists have as a primary fear that of being rear-ended by a car. The apparent priority of rear lighting presumably reduces that fear. Unfortunately, one of these explanations is not based on reality, and from my use of the word ``perceived'', you would be correct in guessing it's not the hardware.

A detailed study of accident statistics in the USA[CF76], found that rear end collisions were responsible for 10.5% of injuries and 37.8% of fatalities in cyclists. Now over 1/3 of fatalities is a significant factor, but cycling fatalities themselves are uncommon, under 1000 every year in the entire United States. Since 2/3 of these fatalities cite `cyclist unseen', a rear light is obviously important and should go a long way towards reducing this risk, but is it enough? Particularly at night, when the cyclist is typically already well illuminated from behind by the headlights of a potential rear-ending vehicle?

Another interesting category of accident is that where the motorist is approaching the cyclist in the opposite direction and turns left into the bike's path. This situation was responsible for 7.6% of accidents, though surprisingly not enough fatalities to register. In this case, a rear light helps not at all, and the cyclist is only marginally illuminated by the motorist's headlights. Looking at head-on collisions caused by either a wrong-way cyclist or motorist adds another 4.4% of injuries and 4.2% of fatalities.

Finally, there is the category of motorists riding into the cyclist's path from a side street or driveway. This was responsible for 18.7% of accidents and 2.4% of fatalities, and here neither the motorist's headlights, nor a cyclist's rear light would be of any use until it is already too late.

In recent years, cycling injuries have outweighed fatalites by in excess of 600 to 1, so while the dangers of rear-ending in the absense of a rear light are not to be ignored, they pale in comparison to the number of injuries potentially related to the absence of a front light.

References

CF76

Cross, K. and Fisher, G. ``A Study of Bicycle/Motor Vehicle Accidents: Identification of Problem Types and Countermeasure Approaches.'' National Highway Traffic Safety Administration, 1976.

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Is a Rear Light Enough?

Brian Edmonds <brian@gweep.ca> February 21, 1998