John Hourdos, Director, MN Traffic Observatory, Civil Engineering
Engineers throughout Minnesota and the rest of the United States receive many requests for residential street warning signs, which are installed to provide drivers with advance warning of potential hazards or conflicts between vehicles and pedestrians. Examples include signs with the standard playground symbol or special word messages such as "Children at Play." The main objective of this study was to estimate the speed impact of these occasional hazard (playground) warning (OHPW) signs along residential streets. Three types of data were collected at each of three study sites approximately one month before and one week to one month after the installation of a pair of OHPW signs. Vehicle speed data were collected with a pneumatic tube device, and manual observations were recorded, focusing on the magnitude and location of the on-street parking and park and/or playground activities occurring at the study sites. Linear regression analysis was used to estimate the change in mean vehicle speed associated with the presence of the OHPW signs while controlling for the effects due to activity levels on the streets and the playgrounds. At one site the OHPW sign had no discernible effect on mean vehicle speeds, while at the other two sites mean vehicle speeds decreased by 1.5 mph and 0.9 mph following installation of the OHPW signs.