In this report a method for the economic assessment of climbing lanes on motorways and all-purpose dual carriageways is identified. The method is based on the use of speed/flow equations derived from data collected at a number of sites with gradients in excess of 3%. The equations differ from standard cost benefit analysis (COBA) speed/flow curves in that they apply to sustained uphill gradients only. COBA curves apply to stretches of road which may comprise a number of uphill and downhill sections. Using the above equations, a series of COBA simulation runs was carried out to assess the benefits of providing a climbing lane along 2 km analysis lengths of two and three lane motorways and all-purpose dual carriageways, under a variety of flow and gradient conditions. Assuming a discounted construction cost of 155,000 pounds per km for a climbing lane, the results indicate that on new two lane roads, a climbing lane would be justified at annual average daily traffic (AADT) (one-way) of 19,000 veh/day for a gradient of 3% and 10% goods vehicle content. If the gradient was 6%, however, the climbing lane would be justified at one way AADT of about 13,000 veh/day. For three lane roads, the corresponding figures would be 24,000 veh/day for 3% gradient, and 15,000 veh/day for 6% gradient. All the above figures refer to low growth conditions. On existing roads, the benefits would be reduced somewhat by construction delay costs, which would require a site-specific queues and delays at roadworks (QUADRO) analysis. Current standards indicate that a climbing lane should only be considered on gradients which exceed 2% for a distance of at least 500 m. As this study has concentrated on gradients in the range 3% to 6%, it is recommended that the economic assessment described above should only be applied to gradients which exceed 3% over a distance of 500 m. The recommended analysis procedure is outlined in the report. For related work see IRRD 822646.

  • Availability:
  • Corporate Authors:

    Transport and Road Research Laboratory (TRRL)

    Wokingham, Berkshire  United Kingdom 
  • Authors:
    • Lee, B H
    • Sriskandan, G
  • Publication Date: 1990


  • English

Media Info

  • Features: References;
  • Pagination: 19 p.
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00609872
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Report/Paper Numbers: CR 143
  • Files: ITRD, TRIS
  • Created Date: Jun 30 1991 12:00AM