2.3: The Wrong Turn on Red

In the 1970s, many parts of the United States began to allow drivers to turn right at a red light. For many years prior, road designers and civil engineers argued that allowing right turns on a red light would be a safety hazard, causing many additional crashes and pedestrian deaths. But the 1973 oil crisis and its fallout spurred politicians to consider allowing right turn on red to save fuel wasted by commuters waiting at red lights.

Several studies were conducted to consider the safety impact of the change. For example, a consultant for the Virginia Department of Highways and Transportation conducted a before-and-after study of twenty intersections which began to allow right turns on red. Before the change there were \(308\) accidents at the intersections; after, there were \(337\) in a similar length of time. However, this difference was not statistically significant, and so the consultant concluded there was no safety impact.

Several subsequent studies had similar findings: small increases in the number of crashes, but not enough data to conclude these increases were significant. As one report concluded,

There is no reason to suspect that pedestrian accidents involving RT operations (right turns) have increased after the adoption of [right turn on red]…

Based on this data, more cities and states began to allow right turns at red lights. The problem, of course, is that these studies were underpowered. More pedestrians were being run over and more cars were involved in collisions, but nobody collected enough data to show this conclusively until several years later, when studies arrived clearly showing the results: significant increases in collisions and pedestrian accidents (sometimes up to \(100\)% increases).^{27, 48} The misinterpretation of underpowered studies cost lives.