In a signal-controlled road network, the average delay incurred by traffic is a function of the network cycle time and signal settings, and the traffic pattern in the network. Techniques exist for calculating signal timings to minimise average delay in the network for a particular choice of network cycle time and for a given traffic pattern. No allowance is made in these calculations, however, for likely consequent changes in the traffic pattern brought about by drivers endeavouring to minimise their journey time through the network. Techniques also exist for assigning traffic to routes through the network in such a way that each individual driver minimises his travel-time, provided that the travel-time on each link of the network is a suitable increasing function of the flow of traffic on that link. In the case of a signal-controlled network, these functions will depend in the first instance on the given signal settings at the particular downstream junction, and suitable expressions exist for the particular case of random arrivals of traffic at the junction. In general, however, and especially if a network of quite short links is being considered, the flow of traffic on a link is not random, because of platooning at the upstream junction. Use has been made of a general procedure for estimating the relationships between travel-time and traffic flow for all the links of a signal-controlled road network for any given signal timings in a form suitable for use in assignment calculations. The techniques of traffic control and traffic assignment have then been combined to enable the calculation of mutually consistent signal timings and traffic assignment by means of an iterative procedure. There will usually be, in principle, many solutions to such calculations for a given network and given origin-destination movements, and a case is described in which two quite distinct solutions have been found for a small realistic network, using as a starting point in each instance some preconceived initial assignment of traffic. If such distinct traffic patterns can be induced in practice, by implementing the corresponding signal timings, there will be scope for choosing between them on grounds such as safety and environment as well as delay to traffic. /Author/TRRL/

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    Newcastle-Upon-Tyne University, England

    Transport Operations, Claremont Tower, NE1 7RU
    Newcastle-Upon-Tyne, Northumberland,   England 
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  • Publication Date: 1977-1


  • English

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  • Accession Number: 00164261
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Report/Paper Numbers: Monograph
  • Files: ITRD, TRIS
  • Created Date: Jan 30 1978 12:00AM