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 22101 Tel: (202)493-3317 Email: wei.zhang@dot.gov
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
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.
These are not mini-roundabouts
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
Advantages of Mini-roundabout Fit into existing intersection ROW More than twice the capacity of AWSC High operating efficiency and safety Lower cost
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
Mini-Roundabout at S Tollgate Rd and W Macphail Rd Bel Air, MD
Source: Jeff Stratmeyer, Harford CO, MD
Relocating This Pole May Cost $400,000 Source: Jeff Stratmeyer, Harford CO, MD
Law Department: No Source: Jeff Stratmeyer, Harford CO, MD
Source: Jeff Stratmeyer, Harford CO, MD
Completed Project Project cost: $175,000 (including 3 LED lights) Project duration: 3 weeks
Potentially Serving Capacity = 1328 VPH 15:30 11 106 47 60 224 23.9915MPH 83.25F Dry 15:45 15 111 55 58 239 22.4391MPH 81.5F Dry 16:00 16 97 54 79 246 22.6796MPH 81.5F Dry 16:15 13 143 46 75 277 23.3999MPH 80.25F Dry 16:30 15 119 46 86 266 22.3959MPH 79.25F Dry 16:45 14 152 44 91 301 21.3944MPH 78F Dry 17:00 16 123 51 88 278 22.4454MPH 77F Dry ***17:15 19 144 46 105 314 22.6773MPH 75.5F Dry 17:30 16 138 31 102 287 21.6894MPH 75F Dry 17:45 20 120 35 104 279 22.4774MPH 74F Dry 18:00 11 124 35 90 260 24.1475MPH 74F Dry 18:15 13 121 36 81 251 23.0521MPH 73F Dry 18:30 10 118 31 69 228 22.2511MPH 72F Dry 18:45 10 121 23 63 217 21.0658MPH 72F Dry Max 15-minute Counts 20 152 55 105 332 Potential Traffic Served: 1328 VPH
Results Reduced potential for serious accidents Before, 85% vehicles >= 38 mph and right angle conflicts 2009 3 accidents: 1 PDO, 1 minor injury, 1 incapacitating injury 2010 2 accidents: 1 PDO, 1 minor injury 2011 1 PDO After, 90% vehicles at <=15 mph and side swipe conflicts 2012 2 PDOs 2013 1 PDO Improved safety for pedestrians and bicyclists.
Mini-roundabout at SR 11 and SR 124 Jackson County, GA Problem: About 50 cars recurring queue on SR 11 SB
Time Range Volume Counts EB SB WB NB Total 0:00-1:00 16 11 18 0 45 1:00-2:00 14 4 13 0 31 2:00-3:00 5 3 8 3 19 3:00-4:00 5 5 14 0 24 4:00-5:00 27 11 34 4 76 5:00-6:00 59 30 83 12 183 6:00-7:00 190 103 202 27 521 7:00-8:00 375 381 407 48 1211 8:00-9:00 172 105 261 26 564 9:00-10:00 128 102 229 22 481 10:00-11:00 145 115 225 28 513 11:00-12:00 138 96 243 18 495 12:00-13:00 172 117 226 23 536 13:00-14:00 179 111 253 20 561 14:00-15:00 196 129 305 24 654 15:00-16:00 186 185 490 34 894 16:00-17:00 240 199 414 30 882 17:00-18:00 288 207 526 34 1054 18:00-19:00 223 160 391 40 813 19:00-20:00 117 81 199 23 418 20:00-21:00 95 91 182 32 399 21:00-22:00 62 41 112 8 222 22:00-23:00 31 16 81 3 130 23:00-0:00 23 17 47 1 88 Total 3082 2315 4959 454 10809 Potential Traffic Served 1. 358 x 4 = 1432 VPH 2. 384 x 4 = 1536 VPH 6:45 76 46 50 11 182 26 MPH 7:00 105 53 74 16 248 25 MPH 7:15 93 76 81 12 261 25 MPH 7:30 85 130 120 10 345 23 MPH 7:45 93 123 133 10 358 23 MPH 8:00 53 28 79 7 167 26 MPH 105 +130 +133 +16 =384
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 35 30 25 SB WB NB Total 20 15 10 5 0 0 10 20 30 40 50 60 70 80 Speed (mph)
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
After Before Safety Results Year Total Crashes # of Injury Crashes 2009 7 (6 rear end, 1 single vehicle) 2 2010 7 (6 rear end, 1 angle) 4 2011 3 (3 rear end) 2 2012 8 (6 rear end, 2 angle) 0 2013 7 (4 rear end, 3 angle) 0
2 mini-roundabouts at Frontier Village Shopping Center in Lake Stevens, WA
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
AWSC Intersections Year 2010 Mini-Roundabouts Year 2010 Year 2016 Year 2016
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.
Before and After Crashes Lake Stevens Mini-Roundabouts Period No. of months No. of crashes Crash per year Before 03/2007-03/2012 60 22 4.40 After 07/2012-12/2013 18 5 3.33 Period K Fatal A Incapacitating Injury Crash Severity B Nonincapacitating Injury C Possible Injury O No Injury U Unknown Before 0 0 0 5 16 1 22 After 0 0 0 2 3 0 5 Total
Before Period 39 th St and Canterbury Rd Baltimore, MD
After Period 39 th St and Canterbury Rd Baltimore, MD
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
Questions? Wei Zhang, Ph.D., P.E. Program Manager FHWA Intersection Safety R&D 202-493-3317 wei.zhang@dot.gov