Progressive deterioration in the operational performance of the large conventional roundabout at the A40/A4020/A412/M40 intersection in Denham resulted in the design by Buckinghamshire County Council of a new two-way circulatory (or ring) system. The system came into operation in December 1982 and was intended to eliminate the previously heavy peak-hour queueing and to improve safety by reducing speeds within the junction. This article describes the results of surveys carried out to assess the traffic performance of the Denham Junction before and after the conversion. The surveys were designed to provide measures of traffic flow patterns, total queueing delay, delay per arriving vehicle and geometric delay for use in the calculation of system benefits. Overall at least 27000 vehicle-minutes of queueing delay were estimated to be saved on an average weekday as a result of the conversion, representing an annual cost saving of 36700 pounds sterling at 1983 prices. There was some indication that accidents after the conversion have been less severe but it was too early to draw firm conclusions since the scheme had been in operation for only just over a year. (TRRL)

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  • Corporate Authors:

    Printerhall Limited

    29 Newmart Street
    London W1P 3PE,   England 
  • Authors:
    • Wright, P T
    • SEMMENS, M C
  • Publication Date: 1984-9

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Filing Info

  • Accession Number: 00392965
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD, TRIS
  • Created Date: May 31 1985 12:00AM