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Abstract
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Highway fatalities increased in response to certain messages.
With 1.35 million people killed in road crashes worldwide each year (1), highway agencies search for ways to reduce traffic deaths and injuries, including encouraging safer driving behaviors. Electronic dynamic message signs (DMSs) (see the photo) are viewed as highly effective devices for communicating traffic safety messages directly to the driving public with the goal of improving road safety (2). However, the actual effects of such DMS messages on road safety have never been evaluated in a rigorous manner. On page 370 of this issue (3), research by Hall and Madsen suggests that, contrary to expectations, displaying traffic fatality numbers in traffic safety messages on DMSs is associated with an increase in crashes downstream.
Beginning in 2012, the Texas Department of Transportation (TxDOT) began posting traffic safety messages for 1 week per month on its statewide network of nearly 900 DMSs. Messages consisted of a traffic safety slogan (e.g., DON'T DRINK AND DRIVE) and the cumulative number of traffic fatalities that year on Texas roadways (XXX TRAFFIC DEATHS ON TEXAS ROADWAYS IN 2012). These messages were displayed when the signs were not used for conveying other transportation-related information about incidents, roadwork, or special events. The rest of the month, fatality information was not displayed.
Hall and Madsen compared crashes downstream of DMSs across the state during periods when traffic safety messages with fatality numbers were being displayed versus not being displayed. To control for other possible factors influencing their results, they also compared crashes on those same roadway segments before the fatality message campaign began and on roadway segments upstream of the DMSs. They concluded that the display of traffic safety messages with fatality numbers resulted in a 1.35% increase in traffic crashes up to 10 km downstream of the DMSs.
Hall and Madsen contend that these results suggest that messages with fatality numbers are overly salient to drivers. They do not discuss the valence of emotions that fatality messages induce, but instead focus on their salience in the working memory of drivers leading to cognitive distraction, which leads to driving errors. The finding seems inconsistent with other research that has found that the use of fatalities and other statistics in traffic safety campaigns is mostly ineffective in influencing driver attitudes or behaviors, in large part because of "optimism biases" held by most drivers regarding their abilities to operate a vehicle and avoid becoming involved in a fatal crash (4, 5). However, because the effect of the fatality messages was greater in urban areas, the issue may be one of excessive salience or of some cognitive overload. Given the greater baseline cognitive demand of multilane urban freeways compared with rural highways, the additional cognitive load induced by fatality messages may be enough to push some drivers beyond their attentional capacity. Such effects of attentional overload have been demonstrated in driving simulations, naturalistic driving studies, and closed-course evaluations...
Language: en |