Evaluating the Impact of Length Variation on Double-Lane Roundabout with an Additional Lane Design

Roundabouts when compared to signalized intersections lack research on means of improving their operations due to increased traffic flow. Signalized intersections usually go through several modifications to improve safety and performance from time to time due to new developments or simple increases in traffic flow. In case of a roundabout, what modification measures can be applied to improve performance? The roundabout entry has been found to have the most significant effect on operation, and this paper evaluates several modification measures that can be applied to the entry of a roundabout to improve operation. In this research, a hypothetical four-leg, double-lane roundabout with additional lane design at the entry is analyzed. The additional lane lengths are varied at the entry in order to study the effect of different additional lane lengths on roundabout operation. Similar length variations are applied to an existing roundabout with known data after calibration and validation. Results indicate that shorter lengths are more effective in reducing delay and improving performance. Findings from this study are intended to provide transportation professionals quantitative means of improving existing roundabout operational performance and also help design future roundabouts with appropriate additional lane lengths that yield better performance. While the design of an additional lane differs from a flared entry, findings from this study can also be applied to flare lengths if they are designed to operate in a similar fashion as additional lane entry.

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• Supplemental Notes:
  • This paper was sponsored by TRB committee ANB75 Roundabouts.
• Corporate Authors:

  Transportation Research Board

  500 Fifth Street, NW
  Washington, DC  United States  20001
• Authors:
  • Hammond, Samuel
  • Hunter, Christopher
  • 0000-0002-9665-9306
  • Chang, Kevin
  • 0000-0002-7675-6598
• Conference:
  • Transportation Research Board 94th Annual Meeting
  • Location: Washington DC, United States
  • Date: 2015-1-11 to 2015-1-15
• Date: 2015

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; References; Tables;
• Pagination: 12p
• Monograph Title: TRB 94th Annual Meeting Compendium of Papers

Subject/Index Terms

• TRT Terms: Approach lanes; Design capacity; Geometric design; Length; Measures of effectiveness; Roundabouts; Traffic delays; Traffic lanes
• Identifier Terms: VISSIM (Computer model)
• Geographic Terms: Brattleboro (Vermont)
• Subject Areas: Design; Highways; Operations and Traffic Management; I21: Planning of Transport Infrastructure;

Filing Info

• Accession Number: 01558163
• Record Type: Publication
• Report/Paper Numbers: 15-5636
• Files: PRP, TRIS, TRB, ATRI
• Created Date: Mar 30 2015 9:33AM