(KNSI) — A new study shows displaying the highway crash-related death tolls on electronic billboards causes more crashes.

Officials chose to display these messages only one week each month. University of Toronto Assistant Professor Jonathan D. Hall and U of M Carlson School of Management Assistant Professor Joshua Madsen evaluated the effect of displaying crash death totals on highway message boards.

According to a research brief from the U of M, researchers compared crash data from before the campaign (Jan. 2010 – July 2012) to after it started (Aug. 2012 – Dec. 2017) and examined the weekly differences within each month during the campaign. They say there were more crashes during the week with fatality messaging than weeks without. The research mainly focused on the state of Texas, where they found fatality messages cause an additional 2,600 crashes and 16 deaths per year at an annual cost of $377 million.

It’s a common awareness campaign tactic, but they discovered that displaying a fatality message increased the number of crashes over a six mile stretch of road where the billboards were located by 4.5%. The effect was worse when the display was larger and too attention grabbing, which hampered drivers’ ability to respond to changing road conditions. Crashes increased in areas where drivers experienced higher cognitive loads, such as heavy traffic or driving past multiple message boards.

“Driving on a busy highway and having to navigate lane changes is more cognitively demanding than driving down a straight stretch of empty highway,” said Madsen. “People have limited attention. When a driver’s cognitive load is already maxed out, adding on an attention-grabbing, sobering reminder of highway deaths can become a dangerous distraction.”

However, the researchers found 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.

“Distracted driving is dangerous driving,” said Madsen. “Perhaps these campaigns can be reimagined to reach drivers in a safer way, such as when they are stopped at an intersection, so that their attention while driving remains focused on the roads.”

They also say the billboards are ineffective because people don’t respond or change their behavior because of a sign.

Versions of highway fatality messages have been displayed in at least 27 U.S. states.

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