Speed kills

For those of a certain age, the phrase “speed kills” may have many connotations. But today, we’re talking about the (literal) impact of increased speed limits on pedestrian injuries and deaths.

A 2011 study by the AAA Foundation for Traffic Safety, looking back at prior similar studies with update data, concluded:

Results show that the average risk of severe injury for a pedestrian struck by a vehicle reaches 10% at an impact speed of 16 mph, 25% at 23 mph, 50% at 31 mph, 75% at 39 mph, and 90% at 46 mph. The average risk of death for a pedestrian reaches 10% at an impact speed of 23 mph, 25% at 32 mph, 50% at 42 mph, 75% at 50 mph, and 90% at 58 mph. Risks vary significantly by age. For example, the average risk of severe injury or death for a 70‐year‐old pedestrian struck by a car travelling at 25 mph is similar to the risk for a 30‐year‐old pedestrian struck at 35 mph. 

Why is that important? Because we regularly have drivers complain that lower speed limits are frustrating… I guess because it takes them two seconds longer to get down your average block. However, if that average block is also used by pedestrians and cyclists, a higher speed limit can bring a higher likelihood of injury or death.

That’s not factoring in how much over the speed limit most drivers typically drive… so if a 20 mph limit really means, say 25 mph, raising that even just 5 mph can double the likelihood of injury or death to pedestrians or cyclists. (That’s also not looking at vehicle design and its impact on injury, a topic for another day.)

So when you hear a clamor from motorists to raise speed limits even a moderate amount, remember that decision has consequences for people who walk or ride amidst those faster-moving vehicles. And if you ride or walk on those roadways, remember that the patience you show behind the wheel can be paid back when you’re a more vulnerable user of that thoroughfare.

Featured in BikeWalkLee newsletter from August, 2021