AbstractWhen drivers are approaching a signalized intersection at the onset of ayellow change interval, they must decide whether to stop or cross theintersection. This can be a difficult decision when the vehicle is locatedwithin the dilemma zone and the result is sometimes a rear-end crash due to asudden stop. Dilemma zone is defined as an area close to an intersection inwhich a vehicle can neither stop safely before the intersection nor clear theintersection without speeding before the red signal comes on. This research studiesthe driver behavior during the amber onset in the signalized intersection.One signalized intersection was selected in Damascus city to collect data forthis purpose. Data was collected using video recording technique. Data wereabstracted, processed and analyzed using programs developed for this purpose. Thestudy examined 226 drivers on the amber onset, 42.47% of them were found to beconflicted by the dilemma zone phenomenon. 51.25% of them conflicted withaccelerating, 42.5% who stopped abruptly, and 6.25% who passed during the redsignal.Key words: dilemma zone, amber onset, clearing distance, stopping distance