In 1995, the first Design, Build, Finance and Operate (DBFO) contracts were introduced for construction of privatised parts of the UK road network. In an attempt to match private contractors' income to road use, a significant proportion of payments to them is directly based on total traffic flow over the scheme. This `shadow tolling' revenue is important, and also needs to have fair payments. This paper addresses the challenge faced by industry in supplying suitable shadow tolling systems, and the solutions developed to provide fully compliant tolling systems well ahead of the required schedule. Vendors providing traffic counting equipment for shadow tolling on DBFO schemes have had to conduct considerable research and development (R&D) to provide a package meeting the strict technical requirements specified by the UK Government. Problems discussed in the paper include: (1) measurement of traffic with a low proportion of heavy goods vehicles (HGVs); (2) congested traffic; (3) straddling, contraflow, and traffic management; (4) the ADR-4000 traffic count analysis system, which uses the Idris algorithm for classifying and counting vehicles; and (5) a new verification method involving automatic vehicle identification, calibration for length measurement, and estimation of classification accuracy.
Abstract