Are Roundabouts Environmentally Friendly? An Evaluation for Uniform Approach Demands
With an increased prevalence of roundabouts in the United States, including roundabouts in the design alternatives can be beneficial from an efficiency, safety, and environmental standpoint. Studies have compared roundabouts with other intersection control strategies; however they are restricted to specific cases. These studies have suggested that when using environmental measures of effectiveness roundabouts can have few emissions and lower fuel consumption levels when compared to unsignalized intersections and can be better for lower demands than signalized intersections. However, some studies have not found this to be the case In this study a generalized intersection with four single lane approaches with equal demand on all approaches was modeled to determine the control with the least fuel consumption, carbon dioxide, carbon monoxide, hydrocarbons and nitrogen oxide emissions. This study demonstrates that fuel consumption and CO2 emissions depend upon turn demand and overall demand. Roundabouts can reduce fuel consumption and CO2 emissions when left turn demands are lower than 30% of the overall demand or when left turn demand is less than 50% of the overall demand and right turn demand is greater than 10%. For most demands and turning ratios, roundabouts can also improve CO, HC and NOx emissions over traffic signal, two-way stop, and all-way stop control alternatives.
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Supplemental Notes:
- This paper was sponsored by TRB committee ADC20 Transportation and Air Quality
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Corporate Authors:
500 Fifth Street, NW
Washington, DC United States 20001 -
Authors:
- Jackson, Meredith
- Rakha, Hesham A
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Conference:
- Transportation Research Board 91st Annual Meeting
- Location: Washington DC, United States
- Date: 2012-1-22 to 2012-1-26
- Date: 2012
Language
- English
Media Info
- Media Type: Digital/other
- Features: Figures; References;
- Pagination: 22p
- Monograph Title: TRB 91st Annual Meeting Compendium of Papers DVD
Subject/Index Terms
- TRT Terms: Environmental impacts; Exhaust gases; Fuel consumption; Highway design; Intersections; Pollutants; Roundabouts
- Subject Areas: Design; Energy; Environment; Highways; I15: Environment; I21: Planning of Transport Infrastructure;
Filing Info
- Accession Number: 01366623
- Record Type: Publication
- Report/Paper Numbers: 12-0789
- Files: PRP, TRIS, TRB
- Created Date: Mar 30 2012 7:19AM