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Abstract: Macroscopic fundamental diagrams (MFD) of traffic for some networks have been shown to have similar shape to those for single links. They have erroneously been used to help estimate the level of travel in congested networks. We argue that supply curves, which track vehicles in their passage through congested networks, are needed for this purpose, and that they differ from the performance curves generated from MFD. We use a microsimulation model, DRACULA and two networks, one synthesizing the network for Cambridge, England, and one of the city of York, England, to explore the nature of performance curves and supply curves under differing patterns of demand. We show that supply curves differ from performance curves once the onset of congestion is reached, and that the incorrect use of performance curves to estimate demand can thus seriously underestimate traffic levels, the costs of congestion, and the value of congestion relief measures. We also show that network aggregated supply curves are sensitive to the temporal distribution of demand and, potentially, to the spatial distribution of demand. The shape of the supply curve also differs between origin–destination movements within a given network. We argue that supply curves for higher levels of demand cannot be observed in normal traffic conditions, and specify ways in which they can be determined from microsimulation and, potentially, by extrapolating observed data. We discuss the implications of these findings for conventional modelling of network management policies, and for these policies themselves. [Copyright &y& Elsevier]

The article discusses key issues concerning the prospects for organizational change in the transportation industry of London, England, in 1982. Key issues discussed include foreign models that are cited as solutions to London's unsatisfactory transport planning arrangements, the key stipulations of the House of Commons Committee on Transport's recommendations aimed at resolving the inadequacies of the city's transport planning and the issues' implications for transportation policy and public administration.

The article discusses the report published by the Select Committee on Transport about the organization and financing of transportation in London, England. The proposed arrangements fall short of what the Select Committee on Transport had in mind in preparing its report and the Transport Bill make things even worse. Of the 12 principles, only two are implemented as a result of the proposals for the city and these are the integrated transport and land use planning and the representation of the national interest.