Abstract: By using the safety laser scanner and the speed control module, the active safety system installed on the suspended rail transit inspection vehicle can detect obstacles within 1.5 m of the inspection vehicle and alert the driver to decelerate. If the obstacle is within 1.2 m, the system will send out a danger signal to the PLC (programmable logic controller) and automatically control the motor braking. A simulation result shows that in case of unexpected conditions while in normal patrol, the vehicle can stop after about 0.34 seconds and glide only 0.8 m. The system has passed safety test smoothly when tested on the hanging monorail experimental line of Qingdao Sifang Locomotive and Vehicle Co., Ltd., the result verifies the accuracy and reliability of the active safety system. Since the system can avoid possible accidents effectively, it meets the requirements of safe operation for patrol vehicles.