Car Travel Time Variability on Links of a Radial Route in London: Results

This working paper describes the results of a study of the variability of travel times and its causes on links of a secti.on of the A41 radial route in north London in the spring and summer of 1987. The objectives were to estimate the extent of variability of travel times of private car users and to explain the observed variability by means of models incorporating a range of traffic factors, including traffic flow, and incorporating seasonal differences. In general the spring was slower and showed more travel time variation between time periods than the summer. slower and more variable links in the spring tended to behave similarly in the summer. The models produced explained around two thirds of the travel time variation between periods, but the explanatory power and explanatory variables differed between links. Blocking of the downstream exit from links was the single variable which was significant in affecting traffic times on most links

Travel Time Variability of a Group of Car Commuters in North London

This working paper describes a study of the variability of journey times of a panel of fifteen commuters using one north London radial corridor, over a total of seven weeks in the spring and summer of 1987. The objectives were to gain preliminary information on the extent of journey time variability and on the commuters* perception of and responses to the variability they experienced. The procedure for selecting the panel and contacting them is described, together with the data collection method, which consisted principally of panellists using tape recorders in their cars to record the time at which fixed points along the route were passed on each day's journey to work. Early or late arrival and its consequences in relation to the day's tasks were recorded at the destination. Analyses are presented of the distributions of times of complete and partial journeys, of the relationship between journey duration and variability and of the effects of diversion in response to perceived traffic conditions. The safety margins needed to ensure given percentages of punctual arrivals were estimated and contrasted with those from previous studies. Further analyses are presented indicating the general unimportance of punctuality for these panellists, the effects of significant lateness when it did occur, and of the panellists' ability to predict their arrival times in advance. A study of highway link travel time variability and its causes was also carried out for cars at the a same time in the same corridor. The methodology, surveys and data processing of this parallel study are set out in ITS Working - Paper 278, and the results and analysis in ITS Working Paper 279

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

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

Road Pricing: The Potential for Comparative Monitoring. A Report to the London Planning Advisory Committee.

This study was designed to review the proposals for road user charging in the Randstad, Stockholm, Oslo and Singapore, to determine the intentions for monitoring of each of these proposed schemes, to assess the implications for the development of policy in London, and to identify any opportunities for obtaining experience which would help in clarifying the uncertainties associated with proposals for road pricing in London. The study reviewed the objectives and operational requirements for road pricing in London and the criticisms levelled against such proposals. On this basis it developed a series of requirements for monitoring and information gathering to help clarify the outstanding uncertainties. These were used as a check list for a series of discussions with those responsible for proposals in the case study cities. Discussions indicated that the proposals in most cities had changed markedly in the period since the study was commissioned. These changes, and the resulting nature of the proposals, meant that only the proposals for Stockholm were sufficiently similar to those in London to justify collaborative monitoring. The report recommends that such collaboration be developed. However, both the Randstad and Oslo schemes offer the opportunity for obtaining information on actual or predicted user response, while the Singapore proposals will provide valuable experience of new technology. It is recommended that all of these are pursued. The discussions highlighted several lessons of direct relevance to the development of policy in London. In particular it is seen as important to keep the specification of the measures simple; to pursue extensive consultation with those who might be affected and with all political parties and government bodies who might be involved in policy decisions; to provide clear guidance on the anticipated uses of the revenue: and to develop a system which is implemented flexibly, so that problems can be remedied as they arise. In this context, the role of assessment and monitoring is limited. It should not be used to delay decisions; however, once a commitment is made to proceed, experience from elsewhere will be of value in informing the consultations. A carefully designed monitoring programme will be important in assessing and enhancing a scheme once implemented. It is recommended that the monitoring programme should be based on the requirements identified in this report