An improved Mark III system from the Centre for Transport Studies in Leeds is described. It consists of field recording equipment, laboratory transcription equipment and a computer system. Parameters to be recorded are: class of vehicle, lane, direction, speed and distance time. For the timing an electronic method is employed, based on pulse width modulation. Some parts of the equipment are described in detail, e.g. the oscillator used as the primary timing reference, the transcription of the magnetic tape, the computer programs. Commentary on the traffic can be included on standard forms or verbally on a track of the tape. The system can be used simultaneously on three-lane dual motorways. The computer print-out can give: speed frequency distributions, vehicle distance frequency distributions, frequency distributions describing the behaviour of vehicles in platoons, and overtaking frequency distributions.
Abstract