Vehicle loading over-length will influence the passing ability and driving safety.In order to measure the vehicle loading length

a measurement system is researched based on IR light curtain

ultrasonic distance measurement sensor

photoelectric switch sensors and single-chip microcomputer.The software program of the system and hardware system are designed and debugged

the simulation platform of freeway entrance and exit is built up.The system is tested on the simulation platform.The experimental results show that the measurement system has high precision.The system can measure the vehicle loading length accurately in the condition of vehicle queuing because of using double benchmark trigger mechanism.The system can be applied to freeway entrance and exit and can cooperate with other geometry size measurement system and weighing system to realize the vehicle over-limit comprehensive inspection.