Car Travel Time Variability on Links of a Radial Route in London: Methodology, Surveys and Data Processing

Abstract

This working paper is one of a series of three describing research on travel time variability of car drivers using a north London corridor. The objectives of the work described in this report were to determine the amount of variability experienced within short time periods and between time periods, and to explain these variations in terms of simultaneously-recorded traffic factors. This report describes the methodology used, the surveys carried out and the data processing procedures. Data were collected on twelve contiguous links on the A41 between 0730 and 1030 on weekdays in spring and again in summer. Link travel-time distributions for cars were obtained by registration-plate matching using hand-held electronic data loggers. The methods of treatment of spurious matches and outliers, resulting respectively from chance matching of partial registration numbers and from stopping or diverting vehicles, are described. The reasons for selecting particular explanatory traffic variables are presented, together with a description of the methods of data collection. The results of these surveys and their analysis are contained in ITS Working Paper 279. The methodology, data collection procedure and analysis of journey time variability experienced by a panel of car commuters using the same corridor are contained in ITS Working Paper 277