An interesting article by our own Dr. Paul Hsieh, “Traffic Safety Signs May Be Hazardous To Your Health”, brings to light some fascinating research on the topic of road signs and their effect on accidents.
Traffic Safety Signs May Be Hazardous To Your Health
Paul Hsieh, Contributor, I cover health care and economics from a free-market perspective. Forbes.com
Apr 26, 2022,07:21pm EDT
Motorists are inundated with roadside signs while driving. These can include speed limit signs, construction warnings, directions to prominent landmarks, and safety warnings (e.g., “Icy Road Ahead”).
In an interesting paper published recently in Science, researchers Hall and Madsen make a strong case that certain roadside safety warning signs can backfire and actually increase — rather than decrease — the risk of fatal accidents.
As part of a roadside safety campaign, the state of Texas (like many states) regularly displays “dynamic message signs” indicating the number of recent traffic fatalities — e.g., “1669 DEATHS THIS YEAR ON TEXAS ROADS.” However, Texas displays these signs one week every month, providing a natural experiment as to how much those signs reduced accidents.
To their surprise, Hall and Madsen found that the signs did not reduce the number of accidents, but rather the opposite.
Over a period of several years, on the weeks the messages were displayed, car accidents rose by 4.5% on the stretches of road 10 km (6.2 miles) after the signs. This translated to 2,600 more accidents and 16 more deaths each year in Texas, with an estimated annual socioeconomic cost of $377 million.
The researchers also did extensive analysis to control for other confounding factors. For instance, they checked fatality rates for similar stretches of road upstream of the signs, as well as checking data on comparable weeks before the public safety campaign began. They also controlled for weather, holidays, and other factors.
Hall and Madsen argue that these signs caused more accidents due to a combination of increased cognitive overload on the drivers along with high “saliency” (attention-grabbing effect) of a starkly negative message.