Effect of Average Passing Zone Length on Spanish Two-Lane Highways Traffic Performance

The U.S. Highway Capacity Manual (HCM 2010) methodology is used in Spain to evaluate traffic operation and quality of service. Recently, the procedure for two-lane highways was adapted to Spanish conditions. The methodology is largely based on simulations from TWOPAS, which was calibrated and validated with Spanish field data, including the number of passes. However, neither the U.S. nor Spanish procedures consider the possible effect of average passing zone length on traffic performance. The objective of this research is to evaluate the effect of average passing zone length on two- lane highway operation and incorporate it in the analysis methodology, if significant. The TWOPAS microsimulation program was calibrated and validated. Then, it was applied to different scenarios varying the average passing zone length (250 to 5,000 m), directional traffic flow rate, and directional split. Only scenarios with 50% of no-passing zones over the length of the study segment were analyzed. Average passing zone length had a profound effect on traffic performance: percent time spent following (PTSF) could be increased up to 28% between long and short average passing zone lengths (PZL). Very short passing zones (250 m) did not contribute to operational efficiency; and the effect was stabilized for PZL longer than 2,500 m. In fact, increasing PZL from 1,000 to 5,000 m improved PTSF by only about 5% and average travel speed (ATS) about 2 km/h. The HCM 2010 evaluation procedure estimated fairly good ATS and PSTF on balanced flows and passing zones longer than 1,250 m. In other cases, the error between the HCM estimates and the simulation results was up to 22% and similar to scenarios with 100 % of no passing zones. Therefore, some adjustments to ATS and PTSF depending on PZL should be included. The results could be used to better estimate traffic operation on Spanish two-lane highways and should be added to current methodologies.

• Supplemental Notes:
  • This paper was sponsored by TRB committee AHB40 Standing Committee on Highway Capacity and Quality of Service.
• Corporate Authors:

  Transportation Research Board

  500 Fifth Street, NW
  Washington, DC  United States  20001
• Authors:
  • Moreno, Ana Tsui
  • LLorca, Carlos
  • Washburn, Scott
  • Bessa Jr, Jose E
  • Garcia, Alfredo
• Conference:
  • Transportation Research Board 95th Annual Meeting
  • Location: Washington DC, United States
  • Date: 2016-1-10 to 2016-1-14
• Date: 2016

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; References; Tables;
• Pagination: 17p
• Monograph Title: TRB 95th Annual Meeting Compendium of Papers

Subject/Index Terms

• TRT Terms: Average travel speed; Length; Level of service; Microsimulation; Passing zones; Two lane highways
• Identifier Terms: Highway Capacity Manual
• Uncontrolled Terms: Percent time spent following
• Geographic Terms: Spain
• Subject Areas: Highways; Operations and Traffic Management; Planning and Forecasting; I72: Traffic and Transport Planning; I73: Traffic Control;

Filing Info

• Accession Number: 01590251
• Record Type: Publication
• Report/Paper Numbers: 16-0169
• Files: TRIS, TRB, ATRI
• Created Date: Feb 16 2016 2:35PM