At about 80 sites in the rural road network spread throughout the country, continuous measurements are made of traffic flow and spot speed of vehicles during the year. Occasionally, the measuring equipment fails to work, for example because the rubber hoses registering vehicle passages have been cut off by snow ploughs, resulting in a loss of measuring data. Since the intention of the measurements is to obtain data for the whole year, there is a need to provide periods deficient in measurements with data of acceptable quality, i.e. by data substitution. At present, the National Road Administration performs data substitution for traffic flows but not speeds. The aim of the project is to: (1) Examine the extent to which the present routines for substitution of traffic flow data can be improved if attention is also paid to road conditions at the time data were lost; and (2) Study the possiblities and benefit of building up routines for substituting speed data. Based on the analysis performed in the project, the following conclusions can be drawn: (1) In data substitution for traffic flows, it is not justifiable to extend the National Road Administration's standard routines so that attention is also paid to the road conditions prevailing at the time data were lost; and (2) In data substitution for vehicle speeds, it is not justifiable to introduce routines so that attention is also paid to the road conditions prevailing at the time data were lost. It is, however, justifiable in the highest degree to increase the quality of the measurement data. Inspection of the measuring equipment should therefore be intensified in a first stage to prevent data losses longer than seven consecutive days. (A)
Samenvatting