This research report shows that dynamic speed feedback signs (DSFS’s), which display an approaching vehicle speed to the driver, are effective in reducing vehicle speeds. Researchers performed a comprehensive, quantitative review of DSFSs in different contexts. The resulting literature review and statistical meta-analysis provide data that show statistically significant speed reductions across a range of circumstances.
This report looked at vehicle speeds not only when and where signs were activated, but also in locations downstream of the actual sign, as well as the effect after the signs have been deactivated. In all cases, vehicle speeds went down, leading researchers to conclude that DSFSs can be effective tools in saving lives.
A two-page Traffic Tech summary can be found at https://rosap.ntl.bts.gov/view/dot/57510. The full report, Effectiveness of Dynamic Speed Feedback Signs, Vol. 1: Literature Review and Meta-Analysis, and the Vol. 2: Appendices and Annotated Bibliography is available for download at: https://rosap.ntl.bts.gov.