Delays and Diversions of Major Motorway Roadworks
P Hanson, FaberMaunsell, UK
QUADRO is used in the UK to assess the costs of maintenance and road construction.
In addition to the direct construction costs, a substantial proportion of the costs are the delays incurred by drivers. In reviewing the programme of major motorway widening the Highways Agency noted that the assessments involved a considerable extrapolation from the 1980s calibration evidence upon which the model is currently based and that the results were very sensitive to the input assumptions. Recognising the need better to decide whether and how to develop and maintain the motorway network, the Highways Agency commissioned research to address these issues.
The objective of this research project is to develop an improved understanding of the effects of major motorway roadworks and then to provide advice on the best methods for assessing delays and diversions. This investigation is based on new empirical evidence on traffic conditions on busy motorway sections and how these are affected by roadworks operations.
A variety of sites were selected for study covering a range of traffic and local network conditions. New empirical information has been surveyed to understand the effects of on road users.
The investigation has explored demand-related responses, including trip diversion, retiming and suppression. Work has also been undertaken to review the accuracy of current and alternative methods of deriving travel time predictions.
Drawing on this investigation, it is intended that interim guidance, or ?best practice? advice, should be provided on how to apply the results of this investigation more accurately to estimate the delay-related costs of major motorway roadworks.
This paper summarises the results of the two year research programme undertaken to investigate these issues. In particular, the paper will discuss:
* the difficulties of developing robust measures of delays and diversions resulting from roadworks; this has involved evaluation of a range of data sources, which in terms of measuring speeds has included distance based (Automatic Number Plate Reading Cameras, time based (GPS equipped floating vehicle data), and fixed point (traffic master and MIDAS detectors);
* the impacts of roadworks on driver behaviour, drawing both on empirical observations of traffic flow changes and evaluating these in the light of individual survey responses; and
* the predictive deficiencies of standard assignment algorithms in predicting routing behaviour during roadworks, and how these may be addressed.
Association for European Transport