01473840

Component

Simulated delay performance of single-lane roundabouts with an adjacent slip lane (bypass) for right turns is evaluated under varying bus and truck traffic percentages and two slip lane exit types (free-flow and yield). A microsimulation assessment considers experimental balanced flow scenarios with different right-turning bus and truck traffic percentages (low, moderate, and high) and with a proposed dedicated lane, compared to no slip lane. Simulated slip lane right-turning traffic volumes range from 50 to 500 vehicles per hour. Results indicate that average delay of a roundabout with slip lane and under varying bus or truck traffic has confirmed a non-linear relationship with slip lane volumes and is sensitive to changing bus or truck traffic percentages, before oversaturation occurs. As expected, results indicate that a free-flow slip lane exit type significantly reduces total roundabout average delay, compared to having no slip lane with bus or truck traffic. Yield slip lane exit types also reduce roundabout total average delay with bus or truck traffic but to a lesser degree. With a free-flow slip lane exit type designated as a dedicated bus lane, overall average roundabout delay was reduced 12% (the estimated 95% confidence interval of reduction estimated between -19% and -5%). With a dedicated truck slip lane, overall average roundabout delay was reduced 9% (the estimated 95% confidence interval of reduction estimated between -16% and -2%). A dedicated bus slip lane shows a more significant improvement of delay than a dedicated truck slip lane, for a single-lane roundabout. Key words: Roundabout, slip lane, average delay, dedicated bus or truck lane, VISSIM.

This paper was sponsored by TRB committee ANB75 Roundabouts

01470560

13-0151

English

15p

2013

Transportation Research Board 92nd Annual Meeting

Digital/other

Figures; References; Tables

Approach lanes; Buses; Microsimulation; Roundabouts; Traffic delays; Traffic flow; Trucks

VISSIM (Computer model)

Highways; Operations and Traffic Management; I70: Traffic and Transport; I73: Traffic Control

Transportation Research Board Annual Meeting 2013 Paper #13-0151

TRIS, TRB, ATRI

Feb 5 2013 12:11PM