A major report has been issued that for the first time recommends policies to improve the safety of digital billboards by severely limiting appropriate locations for the signs and establishing new criteria governing sign behavior, including the frequency with which the brightly illuminated electronic images should be allowed to change.

Written by renowned human-factors expert Jerry Wachtel, the report, Safety Impacts of the Emerging Digital Display Technology for Outdoor Advertising Signs, was produced as a project of the National Cooperative Highway Research Program (NCHRP) of the American Association of State Highway and Transportation Officials (AASHTO).

Scenic America believes that state and local policies related to digital billboards should be based in the public interest, and not exclusively in the interests of the outdoor advertising industry, as has been the case in most localities until now. Decisions about sign locations, illumination levels, and the frequency with which advertising images rotate, are too often based on the desires of the billboard companies and are not rooted in concerns about aesthetic or traffic-safety impacts. This report gives state and local officials guidance on how to incorporate the public interest into policy decisions by laying out recommendations for sign behaviors and locations based on well-established human-factors principles and the evidence that has emerged from a large compendium of national and international research studies.

Among the report's recommendations for reducing the inherently distracting effects of these brightly illuminated, constantly changing signs, are:

• prohibitions on digital billboards in locations where there are large demands on the driver's attention, such as intersections, stretches of highways with on- and off-ramps, or other complex driving environments;
• requirements that no more than one digital billboard be visible at any time; and,
• standards for the frequency of image rotations that ensure that most drivers are only subjected to one message change.

Currently, for instance, most jurisdictions allow image changes every 4-10 seconds, depending on state and local laws. The report calls for image rotation rates to be be determined for each individual sign by a formula that divides the distance from which the sign is visible by the speed limit of the road. That means, for example, that on a highway where the speed limit is 60 mph and the sign is visible from a mile away, the image could change every 60 seconds; on a commercial street with a 40 mph limit and with the sign visible from a quarter mile, the image could rotate every 23 seconds.

A separate Federal Highway Administration research project on the safety of digital billboards is currently underway, with preliminary results expected at the end of this year and a formal report in early 2010.

The NCHRP report may be downloaded in PDF format here.