The purpose of this research was to develop a model for estimating roundabout delay as a function of the influencing traffic and geometric factors. Fourteen roundabouts were selected from different cities in Jordan. Circulating volume, entry volume, and entry delay were measured during peak and off-peak periods using video cameras. Data on geometric design elements including circulating width, entry width, and roundabout diameter were measured through field survey. An empirical approach was used to develop a delay model as a function of the influencing factors based on a time interval of 15 min. The analysis indicated that geometric variables have significant effects on the roundabout entry delay. The entry width has the greatest influence, whereas the circulating width has the least influence. A comparison between delay models produced using different time intervals showed that, as time interval increases, R 2 increases. The SIDRA delay model was validated using the field delay data, and it was found that it overestimates the delay, especially at high delay ranges. The M/M/1 (random arrivals, random services, and a single service channel) queuing delay model was also validated using the field delay data, and it was found that it estimates delay with high variability, especially for high delay ranges.
