Performance Analysis of the Dowling Multi-Lane Roundabouts in Anchorage, Alaska

Details

• Creators:
  Lee, Ming
• Corporate Creators:
  Alaska University Transportation Center
• Corporate Contributors:
  United States. Federal Highway Administration
• Subject/TRT Terms:
  • Multilane highways
  • Roundabouts
  • Performance measurement
  • Traffic flow
  • Crash rates
  • Highway capacity
  • Traffic volume
• Publication/ Report Number:
  FHWA-AK-RD-12-08 ; INE/AUTC 10.05
• Resource Type:
  Tech Report
• Geographical Coverage:
  Alaska
• Corporate Publisher:
  Alaska University Transportation Center ; Alaska. Department of Transportation and Public Facilities
• Abstract:
  The first multi-lane roundabouts in Alaska were constructed in 2004 at the ramps of the Dowling Road/Seward Highway interchange in Anchorage. These serve as junctions for commuters accessing the Seward Highway. As vehicle traffic in Anchorage continues to grow, however, use of the Dowling roundabouts also increases. The roundabouts are currently operating at or near capacity, with long vehicle queues at their entrances during peak traffic hours. This research project examined the performance of multi-lane roundabouts and how drivers use them. Analysis showed that extended queues were due to unbalanced flow patterns at the roundabouts, causing high circulating flow in front of one roundabout. This high circulating flow resulted in low-capacity, high-delay queue values. Researchers also found that accident rates and danger to pedestrians had increased in the past two years. Modeling traffic flow patterns for several possible alternatives suggested that reducing the eastbound flow rate “upstream” of the roundabout by 70% of the original flow could result in an acceptable level of delay and queue length at the eastbound approach of the west roundabout.
• Format:
  PDF
• Funding:
  DTRT06-G-0011
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/27176/dot_27176_DS1.pdf
• File Type:
  [PDF - 1.63 MB]
• Collection(s):
  University Transportation Centers ; US Transportation Collection
• Main Document Checksum:
  urn:sha-512:5a8036dccdeb7134539b929f4584c4e0cffa93c1119d134e13e946b4cea1ae3be86e40a02d751787ccf8bd3a1b6a39bc29a079067b83e2fb1606b0fca4c25e96