Design and Application of Mini- Roundabout in the U.S.

Transcription

1 Design and Application of Mini- Roundabout in the U.S. ITE MID-COLONIAL DISTRICT & MID-ATLANTIC SECTION 2014 ANNUAL MEETING Session 2B: Roundabouts Not Another YORK in the Road 10:45 to 12:00, May 19, 2014 Wei Zhang, Ph.D., P.E. Program Manager, Intersection Safety R&D Federal Highway Administration 6300 Georgetown Pike, McLean, VA Tel: (202)

2 Outline Mini-roundabout concept Operating principles and design philosophy Status of FHWA Mini-roundabout Evaluation Selected Mini-Roundabout Projects Operational/Safety problems solved by mini-roundabout Q & A

3 Mini-roundabout A single lane modern roundabout with ICD of 50 ft - 90 ft. Distinct feature is a traversable central island (and other raised elements) to accommodate large vehicles.

4 These are not mini-roundabouts

5 Design Philosophy Design the elements for 97% of the vehicles that are known to use the intersection daily Make raised elements traversable by the 1-3% large vehicles that occasionally use the intersection Huge savings in R/W and construction costs when compared to regular sized modern roundabouts

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7 Advantages of Mini-roundabout Fit into existing intersection ROW More than twice the capacity of AWSC High operating efficiency and safety Lower cost

8 FHWA Evaluation Status 12 sites completed as of December, 2013 Takoma Park, MD (2 sites, $25,000 total) Baltimore, MD (2 sites) Lake Stevens, WA (2 sites, $20,000 total) Snohomish Co., WA (1 site, $367,000) Bel Air, MD (1 site, $172,000 + $20,000 LED lights) Elmira, NY (2 sites, $97,500 total) Jefferson, GA (1 site, $63,353) Atlanta, GA (1 site) Recruiting 5-7 sites for evaluation

9 Mini-Roundabout at S Tollgate Rd and W Macphail Rd Bel Air, MD

10 Source: Jeff Stratmeyer, Harford CO, MD

11 Relocating This Pole May Cost $400,000 Source: Jeff Stratmeyer, Harford CO, MD

12 Law Department: No Source: Jeff Stratmeyer, Harford CO, MD

13 Source: Jeff Stratmeyer, Harford CO, MD

14 Completed Project Project cost: $175,000 (including 3 LED lights) Project duration: 3 weeks

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16 Potentially Serving Capacity = 1328 VPH 15: MPH 83.25F Dry 15: MPH 81.5F Dry 16: MPH 81.5F Dry 16: MPH 80.25F Dry 16: MPH 79.25F Dry 16: MPH 78F Dry 17: MPH 77F Dry ***17: MPH 75.5F Dry 17: MPH 75F Dry 17: MPH 74F Dry 18: MPH 74F Dry 18: MPH 73F Dry 18: MPH 72F Dry 18: MPH 72F Dry Max 15-minute Counts Potential Traffic Served: 1328 VPH

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19 Results Reduced potential for serious accidents Before, 85% vehicles >= 38 mph and right angle conflicts accidents: 1 PDO, 1 minor injury, 1 incapacitating injury accidents: 1 PDO, 1 minor injury PDO After, 90% vehicles at <=15 mph and side swipe conflicts PDOs PDO Improved safety for pedestrians and bicyclists.

20 Mini-roundabout at SR 11 and SR 124 Jackson County, GA Problem: About 50 cars recurring queue on SR 11 SB

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22 Time Range Volume Counts EB SB WB NB Total 0:00-1: :00-2: :00-3: :00-4: :00-5: :00-6: :00-7: :00-8: :00-9: :00-10: :00-11: :00-12: :00-13: :00-14: :00-15: :00-16: :00-17: :00-18: :00-19: :00-20: :00-21: :00-22: :00-23: :00-0: Total Potential Traffic Served x 4 = 1432 VPH x 4 = 1536 VPH 6: MPH 7: MPH 7: MPH 7: MPH 7: MPH 8: MPH =384

23 Frequency (%) AM Peak Traffic Bus left turn Truck movement Winder Hwy & Galilee Church Rd, Jefferson, GA (After_10/23/2013) Speed Frequency Distribution 40 EB SB WB NB Total Speed (mph)

24 Project Information Engineering: 4 days Construction: 9 days Work Completion: 7.5 weeks after identification of problem Cost: Curbing $03,510 Labor $19,490 Equipment $09,897 Material $40,474 Total $63,353 Results: recurring 50 cars queue no longer exist

25 After Before Safety Results Year Total Crashes # of Injury Crashes (6 rear end, 1 single vehicle) (6 rear end, 1 angle) (3 rear end) (6 rear end, 2 angle) (4 rear end, 3 angle) 0

26 2 mini-roundabouts at Frontier Village Shopping Center in Lake Stevens, WA

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28 Lake Stevens Mini-Roundabout Sites Problems need to be addressed Recurring queues at T-intersection (PM peak) Queuing on Shopping Center NB made it hard for drivers to get in and out of shopping center Drivers observed running stop signs Businesses at the shopping center feared leaving

29 AWSC Intersections Year 2010 Mini-Roundabouts Year 2010 Year 2016 Year 2016

30 Before Results After Each mini took 2 days to construct, at about $10,000 each. Recurring congestion gone after minis opened to traffic. Traffic became smooth in and out of the shopping center U-Turn possibility at T-Intersection reduced traffic load at NB Shopping Ctr Rd. Parking lot full more often 10-15% sales increase at the SAFEWAY store Positive feedback from Fire Department. Only problem was with local Transit Company that has a policy of not allowing drivers to mount raised curb/surface.

31 Before and After Crashes Lake Stevens Mini-Roundabouts Period No. of months No. of crashes Crash per year Before 03/ / After 07/ / Period K Fatal A Incapacitating Injury Crash Severity B Nonincapacitating Injury C Possible Injury O No Injury U Unknown Before After Total

32 Before Period 39 th St and Canterbury Rd Baltimore, MD

33 After Period 39 th St and Canterbury Rd Baltimore, MD

34 Problems Solved by Mini-roundabouts Remove bottleneck at AWSC intersections Reduce major road approaching speed and provide more gaps to minor road traffic Deliver a solution that wouldn t be possible with regular sized roundabout. Improve intersection safety Improve access for pedestrians and bicyclists Revitalize shopping center

35 Questions? Wei Zhang, Ph.D., P.E. Program Manager FHWA Intersection Safety R&D