Simulation-Based Support for Design and Evaluation of Auxiliary Through Lanes at Signalized Intersections

Auxiliary through lanes (ATL) at signals have long been viewed by traffic engineers as a cost-effective means to increase intersection and corridor capacity on arterials, particularly when right-of-way constraints do not permit the development of full road widening. Experience has shown, however that the ATL, tends to be poorly utilized and therefore does not generate the advertised supplemental capacity sorely needed at the signal. The evidence of ATL under-utilization is well-documented in the literature and raises concerns that investments in such designs may not yield the expected operational improvements. This research, under the auspices of NCHRP 3-98, describes an approach to quantify the motivation for ATL under-utilization, and therefore explains the reason behind the strong empirical evidence. Given the myriad of variables that can impact utilization and performance, a simulation-based approach was selected. From simulation results, the team identified the ATL utilization levels in terms of percentage of all approaching through traffic that minimized delays to ATL users (only). These were mostly in the 10-35% level for a two-through lane approach including the auxiliary lane, a far cry from equal or near equal lane utilization. On the other hand, if the objective (of the traffic engineer) is to minimize all vehicle delays, the corresponding ATL utilization was found to be in the range of 35-50%. While still preliminary, these results pose a dilemma to designers who may expect utilization to be driven by improved design while in fact it may be governed by individual utility maximization of ATL users.


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: 21p
  • Monograph Title: TRB 89th Annual Meeting Compendium of Papers DVD

Subject/Index Terms

Filing Info

  • Accession Number: 01152392
  • Record Type: Publication
  • Report/Paper Numbers: 10-1271
  • Files: TRIS, TRB
  • Created Date: Jan 25 2010 10:33AM