A simple method for estimating journey times and costs directly from maps is described together with the results of a validation experiment involving travel over all types and classes of urban and rural roads both in and out of peak hours. The results are used in conjunction with a computer simulation of a road network, involving 2,300 km of classified and unclassified roads in and around the county of Berkshire, to show that the method can be used to select minimum cost routes, and that the selected routes will not differ from the true optimum by more than about 0.2 per cent averaged over all trips, regardless of journey length. Formulae are obtained which relate the inaccuracy, or excess, of optimum routes selected by the model to the magnitude of error in time or cost estimates on individual road sections, and the effect of junction delays is quantitatively discussed. It is shown that the model should be applicable, without calibration or modification, for all areas of the country. (Author/publisher)
Abstract