Analysis of Crash Characteristics on Freeways with Depressed Medians in Southcentral Alaska

The characteristics of crashes on depressed medians of four freeways in Southcentral Alaska were examined under winter conditions. Cross-median crashes (CMC) were dispersed randomly along the freeways analyzed. CMC were 2.5 times more likely to cause a severe injury crash compared to an in-median crash. Rollovers were 72.9%, a very high percentage, among all median crashes. Median slops of 6H:1V (flatter) and 4:1/5:1 (steeper) were found to have similar frequency of cross-median and rollover crashes. With a median width of 32 ft (excluding inner shoulders), 54.7% of median crashes occurred. With a width of 36 ft, median crashes per mile were the highest for different crash types. As median width increased, in general, median crash frequency decreased. Two regression models were developed: (a) Median rollover crashes were associated with severe injury crashes, driver inexperience, horizontal curves, median width between 26 and 40 ft, surface ice, and specific periods of the day, and (b) CMC were associated with multiple vehicles, light trucks, after sunset on lighted roadways, and pavement rutting. Spatial analysis conducted identified nine top hotspots: five segments on New Seward Highway, three on Glenn Highway including location of median crashes, and one on Minnesota Drive. Six interchanges were identified for detailed examination.

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• Record URL:
  https://rosap.ntl.bts.gov/view/dot/32259
• Corporate Authors:

  Alaska Department of Transportation and Public Facilities

  Research, Development and Technology Transfer, 2301 Peger Road
  Fairbanks, AK  United States  99709-5399

  University of Alaska Anchorage

  3211 Providence Drive
  Anchorage, AK  United States  99508
• Authors:
  • Bham, Ghulam
  • Hafele, Brendan
  • Jones, Kaylin
• Publication Date: 2017-5

Language

• English

Media Info

• Media Type: Web
• Edition: Final Report
• Features: Figures; Maps; Photos; References; Tables;
• Pagination: 85p

Subject/Index Terms

• TRT Terms: Crash characteristics; Crash severity; Injury severity; Logistic regression analysis; Medians; Rollover crashes
• Geographic Terms: Alaska
• Subject Areas: Highways; Safety and Human Factors;

Filing Info

• Accession Number: 01634992
• Record Type: Publication
• Report/Paper Numbers: 4000(128)
• Files: NTL, TRIS, ATRI, STATEDOT
• Created Date: May 19 2017 3:50PM