Multiple Lane Automatic Vehicle Classification (AVC) System
The TDS multiple lane classification system combines two overhead mounted laser scanners per lane to automatically classify vehicles into user defined categories (autos, trucks, buses, motorcycles, etc.). The TDS laser scanner based automatic vehicle profiling system also utilizes pattern recognition for class differentiation.
Data from the overhead profiling scanner is used to form a matrix depiction of the vehicle as seen from the overhead position of the lane position laser scanner. The vehicle detection process is initiated when careful examination of the laser scanner outputs indicates the presence of a vehicle. During periods when no vehicle is being detected the processor periodically polls the lane position laser scanner looking for any indication of a vehicle presence. When the profiling laser is penetrated, the processor uses velocity information from the lane position scanner to determine the position of the vehicle relative to the initial location point set by the profiling scanner. Based upon this position, the profiling scanner is polled at regular predefined distance intervals (as opposed to time). A complete set of data points is transmitted from the laser scanner to the signal/data processor at each sample distance. From this information a vehicle profile is generated. This process continues until the laser scanner no longer contains any indications of a vehicle. At that point the vehicle profile is terminated. The length of the vehicle is determined from the number of individual data sets that are recorded.
Vehicle Length and Height Performance
The expected accuracy of the height reported for a vehicle is +/- 6 inches for vehicle features that are a minimum of 6 inches wide as viewed from the perspective of the vertical laser scanner position.
The expected length accuracy distribution is:
- Vehicle Length less than 20 feet : 95% within 1.5 feet
- Vehicle Length 20 to 50 feet : 95% within 2.5 feet
- Vehicle Length 50 feet to 100 feet : 95% within 5% of actual length
The addition of a fiber treadle to the system design provides for the determination of axles along with their distances from the front edge of the vehicle. A treadle based dual tire detector can also be added to the system in the event that dual tires play a role in the classification scheme.
The average speed of the vehicle through the profiling zone is also determined. The system can also be equipped with front and and/or license plate capture equipment for identification of vehicles for enforcement purposes.
Actual Profile - Laser Automatic Vehicle Classifier System