Establishing Fault in Car-Bicycle Accidents

In 2009 (the last year for which there are statistics), there were 51,000 injuries from bicycle-vehicle accidents in the U.S.; 1,643 of those injuries occurred in Arizona. There were 630 bike accident fatalities nationwide, 25 of which were in Arizona, which was a 31 percent increase in bike rider deaths over the prior year.

When serious motor vehicle-bike accidents occur, the first thing the police and the insurance companies want to determine is who was at fault in causing the crash. Public transportation experts and bicycling advocates are asking the same question as they look for ways to reduce bicyclist injuries and deaths, but that’s not an easy question to answer.

The federal government has never done a study on this topic and individual cities and states do not do a good job of record keeping, so the data is spotty.

• A Washington, D.C., report in 2004 said bicycles were more often to blame.
• A Department of Public Safety report in Minnesota found that car drivers were at fault 51 percent of the time, with failure to yield the right of way being the most common cause.
• A study in Hawaii that looked at car-bicycle accidents from 1986 to 1991 found car drivers at fault more than 80 percent of the time.

In a National Public Radio story on car-bicycle accidents, Arizona bike blogger Ed Beighe researched Arizona accidents in 2009 and found that motor vehicle drivers were at fault 56 percent of the time. The most common type of accident for cars and bicycles was the motorist hitting the biker from behind. This is also the most common type of two-vehicle accident in Arizona.

Dedicated bike lanes are one strategy transportation planners use to decrease the frequency of motor vehicle-bike accidents by minimizing contact between the two. But do bicycle lanes really make a difference?

When bike safety researchers reviewed the limited data available, the evidence suggested that designated bike lanes and bike paths do indeed reduce the risk of bicycle accidents and injuries. New York City saw a 40 to 50 percent reduction in accidents as dedicated bike lanes were added.

Part of the reason for this reduction, said researcher P.L. Jacobsen, is that more people bike when bike lanes are available and there is safety in numbers. After all, the more bikers there are, the more drivers will see them.

But even with improved visibility, the safety of bikers depends upon car drivers understanding how to drive on streets with bike lanes. All too often, drivers will encroach on the bike lane, stopping in the bike lane when making a right turn or driving in the bike lane in advance of a turn a block later.

The evidence suggests that when cities undertake a comprehensive program of infrastructure development and public education – with a network of bike lanes and paths as well as the addition of street lighting and low-angled grades – bicycling rates increase and accident rates decline.