Busting a Common Myth About Speeding

As street safety advocates have repeatedly pointed out, speed kills: in particular, a pedestrian struck by a car going 40 miles per hour is far more likely to die than one struck by a car going 20 miles per hour.

But I’m not sure how many motorists realize this.  A common perspective was once stated by a relative of mine: “Speeding isn’t dangerous. What’s dangerous is when one person is going more slowly than everyone else.”  For example, when other drivers are going 60 miles per hour, and one person is going only 30 miles per hour, the fast drivers might be more likely to rear-end the slow driver, because they are expecting the slow driver to go at their speed.  Thus, fatalities are least likely when everyone is driving 60 miles per hour.

This argument might make sense in the context of a limited-access highway.  On such a highway, it is reasonable for a driver to expect all road users to be traveling at roughly the speed limit (or maybe even a little faster).   Moreover, a lower speed limit might have fairly modest safety benefits, because even a motorist struck by someone going slowly by highway standards (that is, 40 or 50 miles per hour) is still reasonably likely to die or be seriously injured.

By contrast, other types of streets are full of slow-moving, vulnerable road users: not just pedestrians and cyclists, but also cars that are slowly turning into a store or intersection, or cars stopped waiting for a light to change or waiting to yield to oncoming traffic.  In such a situation, it is not practical to expect everyone to go the same speed, and a reasonable driver would be aware of this fact.   It logically follows that on regular streets full of walkers and stopped cars, speed kills: that is, a street where drivers go 40 miles per hour is likely to be the site of far more death and injury than a street with slower traffic.