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Performance Evaluation of Roundabouts for Traffic Delay and Crash Reductions in Oxford

Performance Evaluation of Roundabouts for Traffic Delay and Crash Reductions in Oxford. Mississippi department of transportation State Study 213. Waheed Uddin, PhD., P.E. Professor and Director, CAIT Center for Advanced Infrastructure Technology Department of Civil Engineering

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Performance Evaluation of Roundabouts for Traffic Delay and Crash Reductions in Oxford

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  1. Performance Evaluation of Roundabouts for Traffic Delay and Crash Reductions in Oxford Mississippi department of transportation State Study 213 Waheed Uddin, PhD., P.E. Professor and Director, CAIT Center for Advanced Infrastructure Technology Department of Civil Engineering The University of Mississippi http://www.olemiss.edu/projects/cait/Index.html

  2. Project Overview • Task 1 ─ Collect and Review Pre-roundabout Data • Historical traffic and historical crash data – Provided by MDOT • Prior studies –Traffic and Planning Studies (Completed by Neel-Schaffer on behalf of MDOT) • Plans - (Provided by MDOT) • Task 2 ─ Collect and Analyze Post-roundabout Data • Current available traffic and crash data – Provided by MDOT • On-site traffic data collection – completed by engineering students • Traffic analysis of current traffic data – completed by Graduate student • Task 3 ─ Conduct Road Users’ and Public Survey • Anonymous on-site and telephone surveys • Task 4 ─ Submit and Present Interim Report • Task 5 ─ Finalize Data Collection, Complete Analysis, and Evaluate Results • Task 6 ─ Final Report The overall goal of this study is to assess the performance of a double roundabout interchange at the South Lamer Boulevard Exit on Highway 6 with respect to traffic flow, capacity, safety improvements, benefit/cost, and public opinion.

  3. Prior to the roundabout construction the interchange experienced extreme delay, was a safety concern, and was projected to exceed capacity limitation by 2016. Highway 6 and South Lamar Avenue Interchange The signalized and stop controlled intersections were replaced with a double roundabout interchange, a full roundabout on one side and a teardrop shape on the other. Planned roundabouts on South Lamar Blvd. (courtesy of James Sullivan, MDOT) Current roundabout on South Lamar Blvd. (Google Earth)

  4. Traffic DataIntersection of Hwy 6 Ramps and South Lamar Avenue Collected by The University of Mississippi Engineering Students Dates of Collection: October 12 – 17, 2009 Collection time: 7:00 AM to 7:00 PM Collection intervals: 15 minute Vehicle Class Distribution: Motorcycle, Truck, Bus, Passenger Car

  5. Traffic Analysis Resultsfrom microsimulation software Delay and Speed Results Queuing Results

  6. Emission Rates by Speed and LOS for Light-Duty Vehicles and Trucks g/veh/mi Environmental Impacts of Roundabouts Decrease in vehicular emissions and fuel consumption by reducing idling time at intersection Vehicles stopping at traffic signals and stop signs emit more CO2 when compared to vehicles at roundabouts as the delay and queuing are greater When vehicles are idle in a queue they emit about 7 times as much CO as vehicles traveling at 10 mph. The emissions from a stopped vehicle are about 4.5 times greater than a vehicle moving at 5 mph [environmental impacts of modern roundabouts] * Emission values based on traffic data and speeds from Microsimulation Software.

  7. What Makes Roundabouts Safer? Stop Controlled Intersection Roundabout 7 Contact Points 25 Contact Points • Less Contact Points • Lower Travel Speeds • Geometry • Calmer Drive

  8. Crash data for Highway 6 and South Lamar Interchange AM and PM Crash Data Crash Reduction Pre- and Post- Roundabout Post- Roundabout Daytime crashes were significantly reduced in the first year of the roundabout opening to traffic. The t-test concludes that the installment of the roundabouts do have a significant effect on the number of crashes reduced.

  9. Public Opinion Survey Locations of collection: On-site at two convenience stores adjacent to the roundabouts Random telephone and e-mail surveys Factors: Age Familiarity Favorability Results showed overwhelming approval of the roundabouts and support construction of more roundabouts. Respondents commented…to install improved signage including flashing lights and additional pavement markings, especially at the south roundabout.

  10. Performance Analysis of Roundabouts • Since the replacement of the signal controlled interchange with the roundabout interchange: • Driver delay has reduced by 24%. • Driver idling time has reduced by 77%. • Driver fuel wastage has reduced by 56%. • Travel time through the interchange has increased by 67%, saving drivers approximately $806,018 annually*. • Crashes and crash related injuries have been significantly reduced savings an annual comprehensive cost of $86,008 U.S. dollars. • Drivers favor the roundabouts over the signalized intersections at this location. *Annual total of all vehicles through the interchange.

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