Speed zoning on the basis of the 85th percentile speed in rapidly developing urban fringe areas usually results in the posting of 55 mph speed limits. Although these areas have some urban-like characteristics, no differentiation in speed limits is made between highways in these areas and those in rural locations. Speed zoning below the 85th percentile may be beneficial to drivers in rapidly developing areas, indicating that the area requires additional attention and caution. Presented in this paper are the results of field studies conducted at six urban fringe highway sites in Texas where speed limits were currently 55 mph and rapid urban development was occurring. Speed zones of 45 mph were installed at these sites even though the 85th percentile speed did not warrant the lower speed zones. Spot speed, speed profile, and accident data were collected before and after the speed zones were implemented. No significant changes occurred in speeds, speed distributions, or speed-changing activity at the sites. Likewise, accident rates remained unchanged. It appears that the lower speed zones were not effective in improving safety at these sites.