Summer 2004, p.2

Provocateur: “Safety in Numbers” Redefines Road Safety

The more bicyclists and pedestrians on the road, the more drivers become attentive to them.

The more bicyclists and pedestrians on the road, the more drivers become attentive to them.

A perennial obstacle to bike advocacy is the view that more people cycling means more crashes, injuries and fatalities.

Now, a mounting body of research1, conducted in a wide range of cities, intersections, and time periods, proves just the opposite: as cycling and walking increase, the chance that a given cyclist will be struck by a motor vehicle actually decreases.

The research suggests that the relationship between increased cycling and increased safety varies according to “PJ’s Law”2, named for Peter Jacobsen, the California engineer who documented it in an article in Injury Prevention. He found that doubling the number of cyclists on the road tends to bring about a 1/3 drop in the per-cyclist frequency of a crash with a motor vehicle. By the same token, tripling the rate of cycling cuts the crash rate in half.

So . . . want to make cycling twice as safe? Just triple the number of cyclists!

A wide-ranging group of researchers agree on the main cause for this “safety in numbers” phenomenon: as drivers become more accustomed to seeing cyclists on the road, they become more attentive and cautious overall. As well, with more cyclists there’s a better chance that the “vehicle” next to you is a bike instead of a car. A similar effect is seen for pedestrians: more walkers in a city or on a street means fewer injuries per pedestrian from vehicle crashes.

The implications of these findings are subversive to what police and other authorities consider to be effective traffic safety measures. Tactics like pedestrian barricades, helmet laws, punitive enforcement policies and “safety campaigns” that admonish cyclists and walkers--in sum measures that place the safety burden on walkers and cyclists--actually impede safety by discouraging and reducing the presence of walkers and cyclists. On the other hand, measures that serve to encourage people to bike and walk (e.g. financial incentives to walk and bike, plantings that provide shade, special paths, bike parking, road pricing) are now bona fide safety measures.

Most street-safety campaigns, including those by NYC DOT, place the burden on the potential accident victim, i.e. “Get out of the way of Traffic” or the pedestrian-focused, “Cars Hurt, Stay Alert”. While it’s important that cyclists and walkers understand risk and act accordingly, these types of campaigns convey a powerful negative message: that people are better off driving than being in harm’s way. Their end result may be to make cycling and walking more dangerous to the extent that they encourage people to stay at home or use cars.

Instead of “get out of the way” campaigns, it’s now most evident that we need messages that place the onus, and the discouragement potential, on drivers to increase their awareness of walkers and cyclists. Great Britain is showing the way with its true-to-life and shocking campaigns, “Kill your Speed, Not a Child” and “THINK, Slow Down”, which convey the consequences of driver inattention and aggressiveness. After two years of ads, the proportion of drivers to whom it is “extremely unacceptable” to drive 40 mph in a 30 mph zone increased by 15% over pre-campaign levels. During a one-year airing of the THINK!, Slow Down campaign, drivers exceeding the 30 mph limit fell by 10 percent.

Now there is strong evidence that to make the streets safer we need to support walkers and cyclists instead of maintaining a “blame the victim” mentality. Encouraging walking and cycling--while at the same time making drivers accountable for their conduct--is the way to make streets safer for everyone.

Thanks to Charlie Komanoff for his input on this article.

1 Jacobsen, P. (2003). Safety in numbers: more walkers and bicyclists, safer walking and bicycling. Injury Prevention 9, 205-209.

2 Komanoff, C. (2001). The risk compensation theory and bicycle helmets. Injury Prevention 7, 343-344.