Design Factors That Affect Driver Speed on Suburban Arterials (1769-3)

Driver behavior is affected by many roadway factors. This project investigated which geometric, roadside, and traffic control device variables have an effect on driver behavior on major suburban arterials. Traffic signals and traffic volume were considered within the study site selection and data collection criteria and, therefore, are not included in the analysis. Regression techniques were used to determine how selected variables affect speed at the midpoints of straight sections and horizontal curves. When all variables are considered, the only significant variable for straight sections was posted speed limit. In addition to posted speed, deflection angle and access density classes influence speed on curve sections. Because 85th percentile speed is frequently used to set the posted speed limit, one may expect that one value would be able to predict the other, as is shown in this analysis. Another series of analyses was performed without using posted speed limit so as to provide information on predicting operating speed when not considering posted speed limit. Without speed limit, only lane width is a significant variable for straight sections. For curve sites without speed limit, the impact of median presence now becomes significant along with roadside development.