01025615

English

http://pubsindex.trb.org/orderform.html

Transportation Research Board Annual Meeting 2006 Paper #06-1343

At congested roundabouts approaches, vehicles that join a queue must come to a stop and possibly undergo several stop and go cycles until reaching the yield line of the circulating traffic. As a result, emissions may increase, because of the existence of excessive delays, queuing and speed change cycles for the approaching traffic. The main objective of this research is to quantify traffic and emission impacts for single lane roundabouts in urban corridors. Based on experimental measurements of traffic and using the "Vehicle Specific Power" methodology, the impact of traffic and emission performance of roundabouts is presented. The approach attempts to explain the interaction between roundabout system operational variables (entry volume, conflicting volume and roundabout geometry) and the resulting traffic performance and vehicle emissions. The experimental data for calibrating the numerical traffic model were gathered from two single lane roundabouts located in Lisbon (Portugal) and Raleigh (North Carolina, USA). Using the congestion-appropriate speed profiles of vehicles on roundabout approaches, the emissions calculation methodology is used to quantify the relationships between vehicle dynamics and emissions. The main findings of the present work are: the characterization of three synthetic speed profiles that occur at a roundabout approach, the distribution of these profiles based on congestion levels, and the correlation between queue length and the number of stop and go cycles. Two different types of stop and go driving cycles for vehicles joining the queue at a roundabout were identified: short and long. The length of each cycle depends on the expected queue length at the roundabout and the frequency of each cycle directly impacts the level of vehicle emissions. KEYWORDS: Emissions; Roundabout; Speed profiles; Stop and go; Traffic

BTRIS, HRIS

06-1343

CD-ROM

17p

01020180

2006

Transportation Research Board 85th Annual Meeting

Figures (7) ; References (27) ; Tables (3)

Air pollution; Methodology; Pollutants; Roundabouts; Speed; Traffic models

Design; Energy; Environment; Highways; Operations and Traffic Management; I15: Environment

Jun 8 2006 11:26AM