The Directorate-General for Public Works and Water Management maintains a speed measuring system on motorways to gain insight in the extent to which the speed limits on motorways are complied with. The speed reports use a special selection of locations in the measuring system. These locations there must have an undisturbed traffic flow which leaves the driver 'free' to choose his own speed.
The measuring system maintained by the Directorate-General for Public Works and Water Management has been operational since 1983 and consists of approximately 100 locations. Measuring loops detect the number of vehicles, their lengths and their speeds.
The vehicle type is determined based on its length. Until the first quarter of 2002 the following categories and sizes were used:
New categories and sizes are used since the second quarter of 2002:
This does not seem to have had an effect on the average speed (AVV, 2001)