The new Tantala study -- the third in a series performed for the OAAA -- returned to Cuyahoga County, Ohio, which includes Cleveland and its surrounding suburbs. Tantala reviewed police records for 60,000 traffic accidents taking place in the county over an eight-year period, comparing accident rates from a four-year period before digital billboards were installed with the four-year period following their installation.

Tantala analyzed data documenting the location, time of day, and the direction and speed of the vehicles involved in each accident (including accidents on stretches of road where digital billboards are visible, as well as accidents elsewhere) and found there is no statistical correlation between accidents and visual exposure to digital billboards, by day or night. Rather, Tantala found that overall accident rates in the county have decreased over the last four years, even on stretches of road where digital billboards are visible.

This study reinforces Tantala's findings in its two previous studies of the issue. In April Tantala published the results of its analysis of police records documenting 18,000 traffic accidents that took place in the area of Rochester, N.Y., over a five-year period, which also showed no statistical correlation between digital billboards and accidents. Two years before that Tantala completed its first study of accident rates in the Cleveland metro area for the OAAA.

Around the same time as the first Tantala study, Virginia Tech completed a survey about the effects of signs on drivers. Conducted by the Center for Automotive Safety Research at Virginia Tech's Transportation Institute, the study observed measures like eye-glance patterns, speed maintenance and lane-keeping, and found no substantial changes in behavior patterns in the presence of digital signage.

Traffic safety has been a hot topic in the ongoing public debate over digital billboards, with opponents claiming the displays' bright lights and motion distract drivers and cause accidents. However, the last couple years have also seen increasing opposition on purely aesthetic and economic grounds: some neighborhood associations in Los Angeles, for example, say digital billboards are unsightly and lower property values.

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