Highway overhead distracted driving messages cause more accidents, study finds

The clever signs above highways reminding drivers to buckle up and of the perils of distracted driving might actually be causing more accidents than they’re helping, according to a new study.

A new study by University of Toronto and University of Minnesota professors evaluated the effect of displaying crash death totals on highway message boards. Versions of different fatality messages have been displayed in at least 27 U.S. states previously.

The study focused on Texas, where officials chose to display these messages only one week each month.

Researchers then compared crash data from before the campaign (from Jan. 2010 to July 2012) to after it started (Aug. 2012 to Dec. 2017), and examined the weekly differences within each month during the campaign. 

Results found that displaying a fatality message increased the number of crashes over the 10 km following the message boards by 4.5 percent – an increase comparable to raising the speed limit 3 to 5 mph, or reducing highway troopers by 6 to 14 percent, according to previous research.

The findings suggest fatality messages caused an additional 2,600 crashes and 16 deaths per year in Texas, costing $377 million each year.

It’s also suggested that the "in-your-face" messaging approach weighs down drivers’ "cognitive loads" – temporarily impacting their ability to respond to changes in traffic conditions.

The researchers found the bigger the number in the fatality message, the more harmful the effects. The number of additional crashes each month increased as the death toll rose throughout the year, with the most additional crashes occurring in January when the message stated the annual total. They also found that crashes increased in areas where drivers experienced higher cognitive loads, such as heavy traffic or driving past multiple message boards.

However, the researchers found there was a reduction in crashes when the displayed death tolls were low and when the message appeared where the highways were less complex. Madsen says this suggests that at times the messaging was not as taxing on drivers’ attention.

While the use of highway fatality messaging varies by state, Madsen says agencies should consider alternative ways to raise awareness.