The official project name is "A Real-Time Laser-Based Portotype Detection System for Measurement of Delineatons of Moving Vehicles". The laser project for short. The laser project is part of the California PATH (Partners for Advanced Transit and Highways) Program.
Figure 1: Fieldtesting View of the Laser-Based Detection System
Figure 2: Top View of the Laser-Based Detection System
The laser project is a non-intrusive means of detecting when a particular vehicle enters and exits a section of a highway. The Laser-Based Detection System (LBDS) does this by creating a profile of the entering vehicle. Using this vehicle specific profile, another LBDS further down the highway can then recognize the same vehicle as it passes under it. The LBDS can also utilize the profile of a vehicle to determine the vehicle type and calculate the vehicle's speed.
Currently, when the speed of a vehicle is determined, it is at a point. The measurement is usally made by two loops placed 20-feet apart. Along a given link of road multipule loop systems are place to measure the speed at various locations. These point measurements are then extrapolated to lines depicting the speed of the vehicles along the link. The drawback to this form of measurement is when the speed changes dramtically between two loop systems. This system of measurement gives no information on what each vehicle is doing. There is not a way to tell how long each vehicle takes to move from point a to point b. The only information known is how fast at given points vehicles are moving. An example of the problem is if at one point the speed is 50-mph and at the next point the speed is also 50-mph the extraplation along the link would show that the speed does not change along the link. When what could be happing between the two points is a slow down of traffic that dramaticall increased the time to move between the points. For reasons like this a different system is needed to measure the flow of traffic along a link.
In order to solve this problem a speed measurement system needs to be able to tell when a paticular vehicle enters and exits a link. This information could be acquired through reading the license plates of the vehicles. The problem here is this invades the publics privicy. The laser project is is a nonintrusive means to acquire this data. It is able to make a profile of a vehicle as it passes under the detector. Utilizing this profile, the vehicle can be reidentified for traffic information purposes without any intrusion of the public's privacy.
Figure 3: Boxed Laser-Based Detection System