This report describes the coding system used since the beginning of 1995 for vehicle classification. The codes are part of PREC95, a programme for processing and analysing data from automatic traffic surveys. PREC95 is in turn part of a larger traffic measurement system, TA, which has been developed at the Swedish National Road and Transport Research Institute (VTI). The purpose of this work has been to review, check and document the coding system for vehicle types which is used in the TA system. The decision basis for coding has largely been taken from: (1) vehicle register data on vehicle type and axle distance; (2) traffic measurement data on speeds and axle distances; and (3) video filming with simultaneous recording of traffic measurement data. An important change introduced in the coding system is that the upper limit for axle distances of cars and light trucks has been increased from 330 to 348 cm. This may affect comparisons with earlier traffic measurements. Other changes in the system consist mainly of minor corrections of limits between different types of heavy vehicle. As a result of the changes in the coding system, the traffic measurement system now provides a more accurate description of the traffic passing a measuring point. The work has also led to a somewhat clearer picture of the system's shortcomings. (A)
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