New critique identifies troubling errors in FHWA’s report on driver distraction from digital signs

By Bill Holloway

It is common wisdom that driver distraction, whether due to texting, talking on the phone, or other causes, increases the risk of crashes. A 2006 Virginia Tech study found that 80 percent of crashes involved driver inattention in the three seconds preceding the event.

The federal government began allowing the construction of digital billboards along interstate highways in 2007, and as they have grown much more prevalent there has been a demand for research to determine whether digital signs and billboards present an unreasonable risk of distraction to drivers. In response to concerns over the potential effects of digital billboards on driver attention, FHWA conducted a study to answer the following questions:

  • Do digital signs attract drivers’ attention away from the forward roadway and other driving-relevant stimuli?
  • Do glances to digital signs occur that would suggest a decrease in safety?
  • Do drivers look at digital signs more than at standard billboards?

The study found that while drivers may look at digital signs slightly more than they look at standard billboards, this was not associated with a decrease in drivers’ attention to the roadway or an increase in unacceptably long glances away from the roadway. However, these results contradict studies that have been done elsewhere, including a 2009 study from Sweden that, along with related studies, prompted the country to ban all digital billboards along roadways.

Following the release of the FHWA study, Jerry Wachtel, an expert in the areas of highway safety and distracted driving, identified a number of discrepancies between the draft and final versions of the study, which he felt cast doubt on the study’s conclusions. In January 2015 he released an extensive peer-reviewed critique of the FHWA study that identified the following issues:

  • Use of unproven equipment to detect driver eye movements that resulted in data collection problems;
  • Failure to analyze glances from approaching drivers farther than 960 feet from billboards or very close to billboards on the right side of the road;
  • The brightness of the billboards studied by FHWA averaged only 1/16th the brightness of standard digital billboards, drastically reducing their ability to attract driver attention;
  • The issue of dwell-time, how quickly sign images or text changes, was not addressed; and
  • A variety of other discrepancies between the draft and final versions of the study regarding the number of signs analyzed, their locations, setbacks, and side of the road.

Wachtel worries that if these digital billboards continue “to go up and we later find that they contribute to accidents, it will be very hard or impossible to get them taken down.”

Jerrald Jung, Chairman of the Michigan Transportation Commission, said he “found the [FHWA] study unconvincing.” He took particular exception with the report’s contention that analyses of driver visual behavior, as measured by eye tracking systems, were the best way to evaluate the traffic safety impacts of digital signs.

FHWA officials have not responded Wachtel’s critique or to SSTI requests for comment.

Bill Holloway is a Transportation Policy Analyst at SSTI.