Patent ID: 6925377

Claim:
A tunnel monitoring system for monitoring vehicles in a tunnel having at least one vehicle traffic lane, wherein the monitoring system includes vehicle locating sensors installed in the longitudinal direction of at least one lane ( 2 , 4 ) and distributed along the tunnel; an evaluation unit ( 16 ) to which sensor signals of the locating sensors can be transmitted; and an emitting unit downstream of the evaluation unit ( 16 ) by means of which evaluation results can be displayed; said monitoring system comprising: a plurality of ultrasonic sensors ( 7 , 9 , 10 ) disposed along the length of said tunnel having an emitting and receiving zones ( 11 , 12 ) directed over an area of at least one vehicle lane ( 2 , 4 ) so that when a vehicle ( 3 , 5 ) is present in the emitting and receiving zone ( 11 , 12 ) of an ultrasonic sensor ( 7 , 9 , 10 ), said ultrasonic sensor generates and transmits a sensor signal ( 7 a ); said emitting and receiving zones ( 11 , 12 ) of ultrasonic sensors ( 7 , 9 , 10 ) following each other in the longitudinal direction of the tunnel ( 1 ) adjoin each other at vehicle detection zones that are shorter than a usual vehicle in the longitudinal direction of vehicle travel; an evaluation unit ( 16 ) for receiving said sensor signals from said ultrasonic sensor; and a vehicle running time measuring module included in said evaluation unit using a first sensor signal from a first ultrasonic sensor ( 7 , 9 , 10 ) and a second sensor signal from a second ultrasonic sensor to determine the vehicle running time between said zones of said first and second sensors; and a speed measuring module included in said evaluation unit for determining the vehicle speed from the running time and the known distance between said sensors.