The capacity of signalized intersections is sometimes increased by adding an auxiliary lane for use by through traffic. The effectiveness of an auxiliary lane depends on the amount of traffic using it. Equal distribution of traffic between a continuous and an auxiliary through lane would result in the greatest total capacity of this lane pair, but traffic, land use, and geometric factors are usually such that this does not occur. The 1985 Highway Capacity Manual does not address this situation. A concept of captive and choice lane users was used in modeling auxiliary lane use for intersection configurations with a single continuous through lane and an auxiliary lane beginning upstream of the intersection and extending downstream of it. Stepwise multiple regression was performed on data collected at sites in Tennessee to determine, from a candidate list of factors, those that significantly affect choice use of the auxiliary lane. These factors were found to be (a) through flow rate, (b) right turns off of the facility in the last 500 ft (152 m) of the auxiliary lane, (c) downstream auxiliary lane length, and (d) urban area size. For the sites studied, it was found that traffic distribution between lanes for intersection configurations with a single continuous through and an auxiliary lane is much different from the value given in the Highway Capacity Manual for two continuous through lanes.


  • English

Media Info

  • Features: Figures; References; Tables;
  • Pagination: p. 50-57
  • Monograph Title: Traffic operations: highway capacity
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00713574
  • Record Type: Publication
  • ISBN: 0309061237
  • Files: TRIS, TRB, ATRI
  • Created Date: Nov 21 1995 12:00AM