New Study Suggests Roadside Safety Messages Backfire and Cause More Crashes

Policy-makers have been trying to reduce traffic accidents by implementing safety campaigns in the form of messages posted on roadside billboards and signs.

You may have seen one of these messages. One campaign, for instance, displayed the year-to-date number of statewide roadside fatalities on highway dynamic message signs in 28 states throughout the country.

According to a recent study, however, these signs did not work as intended. Instead of reducing the number of accidents on the road, they increased them.

So-Called Fatality Messages Increased the Number of Crashes

The study appeared in the scientific journal Science in April 2022. Researchers examined the effects of these “fatality messages” in the state of Texas.

The Texas Department of Transportation (TxDOT) showed these messages starting in August 2012 for one week each month. This setup allowed the scientists to measure the impact of the intervention since it occurred at the same time in the same place every month.

They measured data on 880 fatality messages and all crashes occurring in Texas between January 1, 2010, and December 31, 2017. They then estimated how the intervention affected crashes near these signs as well as statewide. They compared these results to those gathered during the weeks before TxDOT started displaying the messages.

The results showed that contrary to policymakers’ expectations, displaying the fatality messages increased the number of traffic crashes.

Safety Campaign Did Not Work as Expected

Here are the specific results of the study:

• During the safety campaign weeks, traffic crashes increased by 1.52 percent within 5 km of the signs, and 1.35 percent over the 10 km after the signs.

• The total effect of the messages over 10 km was determined to be a 4.5 percent increase.

• This increase compared to raising the speed limit by 3 to 5 miles per hour or reducing the number of highway troopers by 6 to 14 percent.

• The total number of statewide crashes during campaign weeks was also higher than during non-campaign weeks.

• The scientists’ calculations suggested that this campaign caused an additional 2,600 crashes and 16 fatalities per year in Texas alone, with a social cost of $377 million per year.

Why Were the Safety Campaigns So Ineffective?

As to why the campaign didn’t work as policymakers hoped, the scientists proposed a distraction theory. They determined that these “in-your-face,” “sobering,” negative messages seized too much attention, interfering with the drivers’ ability to respond to changes in traffic conditions.

In support of this theory, they found the following evidence:

• Displaying a higher fatality count caused more crashes than displaying a small one.

• Fatality messages were more harmful when displayed on more complex road segments.

• Fatality messages increased multi-vehicle crashes.

• The impact was largest close to the sign and decreased over longer distances.

The scientists concluded that their study highlighted five key lessons:

• Fatality message campaigns increase crashes and should be stopped.
• Safety campaigns aimed at changing drivers’ behavior can backfire. The message, delivery, and timing should be carefully designed so as not to overload drivers and cause distraction.
• Individuals don’t necessarily habituate to behavioral intentions, even after years of treatment.
• The effects of these safety interventions don’t necessarily persist after the campaigns stop.
• It’s important to measure an intervention’s effect because good intentions do not necessarily imply good outcomes.