In vehicle actuated traffic signal control, placement of queuing detectors at intersection approaches is an important issue. In many previous studies in the literature and HCM, this issue is not discussed in clearly.. In my opinion, traffic volumes and vehicles speeds must be taken into account while the detectors are placed at intersection approaches. Although I have studied on this issue for a long time, I have faced with some problems about the placement of detectors. I should note that the placement of detectors affect the performance of intersection (positive or negative). If anyone illimunate or give information to me about this issue, I will so grateful for him/her. I am waiting for your valuable comments and suggestions.