London traffic lights are all equipped with PCATS — pedestrian countdown at traffic signal. It’s the timeout signal that shows how many seconds you have left t

London traffic lights are all equipped with PCATS — pedestrian countdown at traffic signal. It’s the timeout signal that shows how many seconds you have left to cross the road. The implementation is very hacker friendly. The PCATS counter is literally bolted onto the side of the existing lights and learns the pattern of the system to which it is attached by monitoring its behavior. There is basically all but an air gap between the counter and the lights themselves, and the counter is making an informed guess. They start their installation-lives having no idea how much time will be left. As such, each counter is equipped with a 4 bit error display to indicate its status — out of sync, could not sync, faulty lights, etc. Keep your eyes peeled for little LEDs telling you something about the internal status of the system. Example: https://uk.yunextraffic.com/portfolio/traffic-signal-control-solutions/signals/pcats-pedestrian-countdown-at-traffic-signals/ https://uk.yunextraffic.com/portfolio/traffic-signal-control... Error codes shown here, on page 7: https://content.tfl.gov.uk/PCaTS-Note-4-Technical-Specification-v03h.pdf https://content.tfl.gov.uk/PCaTS-Note-4-Technical-Specificat...