A tunnel monitoring system for monitoring vehicles traveling through a tunnel
having
at least one vehicle traffic lane is disclosed comprising a plurality of ultrasonic
sensors arranged in series in a longitudinal direction of the tunnel. The sensors
have a detection zone covering a portion of the traffic lane for detecting the
presence of a vehicle in the detection zone, and the ultrasonic sensors generate
a vehicle sensor signal upon detecting a vehicle in the detection zone and a sensor
identification signal identifying which sensor the sensor signal is transmitted
from. The detection zones are projected and arranged in relation to the traffic
lane to provide a generally continuous detection of the vehicles traveling though
the tunnel. An evaluation unit receives the vehicle sensor signals and the sensor
identification signals for monitoring traffic in the tunnel.
