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Traffic signals at intersections have a significant effect on traffic emissions. They interrupt traffic flow and create additional acceleration and deceleration driving modes. Therefore, the objective of this paper is to perform the optimization process of vehicle delay and exhaust emissions at isolated signalized intersections. Three-leg intersection located in Kafr El-Sheikh City, Egypt was selected in this study. Field delay times were estimated based on vehicle speed and acceleration profiles using GPS device. On-road measurements of vehicle speeds and emissions were collected simultaneously for all movements of all approaches at the selected intersection. The micro-simulation software VISSIM was used to model and analyze the selected intersection. The model was calibrated and validated using the collected data. Signal timing model was developed for the selected intersection and used for optimization of delay time and vehicle emissions. It was found that the changing of signal timing was effective in improving the operational and environmental performance of the traffic signal under study. Also, the results indicated that when the traffic flow rate is higher, the optimal cycle time corresponding to the performance index function increases. Optimization of the delay times and exhaust emissions gives traffic engineers the option of minimizing vehicle emissions in the designing of the signalized intersections or timing a signal system. [ABSTRACT FROM AUTHOR]