by traffic-light-man on Wed Mar 20, 2013 6:04 am
The PEEK heads, as far as I know are manufactured from 100% Polypropelene.
The detection systems using the Above Ground Detectors are for the purposes that Lewis pointed out.
There is a Vehicular AGD, however sometimes detection loops are used instead.
There are two pedestrian detectors, one to cancel the call if the pedestrian walks away and the other to hold the signals at all-red if there is still a pedestrian on the crossing after the pedestrian green phase has ended.
There is a range of technology used in AGDs now, including Microwave, Video and Doppler.