An article today from the Washington Post describes a new infrared system for applications in High Occupancy Toll (HOT) lanes. It explains that
The lanes are billed as the salvation of the suffering commuter. Solo drivers will be able to buy their way around congestion, while carpoolers will ride free. But the lanes' success hinges on finding a way to differentiate between paying and nonpaying customers without stopping every vehicle to count heads.The system automagically detects the number of passengers in passing vehicles by bouncing infrared waves off of their skin. This marks a departure from computer vision-based approaches for detection in similar circumstances (for example, automated pedestrian detection).