National Traffic Speeds Survey I: 2007

NHTSA - Behavioral Safety Researchhttps://doi.org/10.21949/15257332012PDFTech ReportHuey, R.De Leonardis, D.Shapiro, G.Freedman, M.Westat, Inc.United States. National Highway Traffic Safety Administration. Office of Behavioral Safety ResearchUnited States. National Highway Traffic Safety AdministrationUnited StatesTraffic regulationsSpeed limitsSpeedingDriver errorsHuman factors in accidentsTraffic safetyDOT HS 811 663DTNH22-02-D-65121TASK ORDER 6Tremont, Paul J.; Collier, Geoff; Atkins, RandolphFinal; Nov. 2006-July 2008.A field survey was conducted during spring and summer 2007 to measure travel speeds and prepare nationallyrepresentative speed estimates for all types of motor vehicles on freeways, arterial highways, and collector roads across the United States. Over 10 million vehicle speeds were measured at more than 700 sites included in the geographic cluster sample of 20 primary sampling units (PSUs). Each PSU was a city, county, or group of two or three counties representing combinations of regions of the United States, level of urbanization, and type of topography (flat, hilly, mountainous). Speeds were acquired on randomly drawn road segments on limited access highways, major and minor arterial roads, and collector roads. Speed measurement sites were selected in road segments with low, medium or high degrees of horizontal and vertical curvature or gradient. Overall, speeds of free-flow traffic on freeways averaged 64.7 mph and were approximately 11 mph higher than on major arterials, which at 53.6 mph were in turn about 7 mph higher than the mean speed of 46.9 mph on minor arterials and collector roads. Most traffic exceeded the speed limits. Nearly half of traffic on limited access roads and about 60% of traffic on arterials and collectors exceeded the speed limit. About 15% of traffic exceeded the speed limit by 10 mph or more on freeways, arterials and collector roads. Speeds of passenger vehicle size classes were generally higher than for medium trucks. Often, speeds of large trucks were higher than medium trucks, and in some circumstances, large truck speeds were higher than passenger vehicles.129