Speed limit-related issues on gravel roads.

Details

• Creators:
  Dissnanayake, Sunanda ; Liu, Litao
• Corporate Creators:
  Kansas State University. Civil Engineering Dept.
• Corporate Contributors:
  Kansas. Dept. of Transportation. Bureau of Materials & Research
• Subject/TRT Terms:
  • Gravel roads
  • Speed data
  • Gravel roads--Kansas
  • Speed limits--Kansas
  • Speed zoning (Traffic engineering)--Kansas
• Publication/ Report Number:
  K-TRAN: KSU-06-5
• Resource Type:
  Tech Report
• Geographical Coverage:
  Kansas
• Edition:
  Final report; Summer 2006-Fall 2008.
• Corporate Publisher:
  Kansas. Dept. of Transportation
• Abstract:
  In the United States, there are nearly 1.6 million miles of unpaved roads. Total length of unpaved roads in Kansas is ; about 98,000 miles, of which about 78,000 miles are gravel roads. Most of the gravel roads are not typically posted ; with speed limit signs but rather are regulated with a 55 mph blanket speed limit established by Kansas statutes. ; Surface conditions of gravel roads are likely to change with time, space, and quality of maintenance work, making ; it even more necessary to have proper control of traffic speeds on these roads. Normally used speed regulations ; and rules for freeways or other types of paved roadways might not be appropriate for gravel roads, especially for ; those local thoroughfares which usually carry very low traffic in rural areas. An extensive literature search revealed ; no specific rules or references to provide guidelines on setting speed limits on gravel roads. Therefore, an effort was ; made in this study to evaluate the effects of currently posted lower speed limits in some Kansas counties based on ; traffic characteristics and safety on gravel roads, with the intention of providing proper guidelines for setting speed ; limits on gravel roads in Kansas. ; Speed analysis on a number of gravel roads where the statutory-imposed, frequently unposted speed limit of 55 mph ; was utilized indicated that they are functioning at a reasonably acceptable level in terms of actual speeds. In order ; to evaluate whether there were differences in traffic speeds between two counties or groups which have different ; speed limit settings on gravel roads, a t-test was used. The analysis found no significant difference between mean ; speeds in two counties, one of which has a 35 mph posted speed limit on gravel roads while the other did not post ; any speed limits. Moreover, mean speed on sections with a 35 mph posted speed was a little higher than on gravel ; roads without any speed limits. Linear models to predict 85th-percentile speed and mean speed on gravel roads were ; developed based on speed data. Both models indicated that traffic speeds are not significantly affected by the speed ; limit, but are related with 90% confidence to road width, surface classification, and percentage of large vehicles in ; traffic. Chi-square tests were conducted with crash data, and the results indicated that the posted 35 mph speed limit ; on gravel roads had not resulted in either smaller total number of crashes or decreased proportion of severe crashes, ; compared to gravel roads where no speed limits were posted. Logistic regression models were also developed on ; four levels of crash severity, which indicated that gravel roads with higher speed limits are likely to experience a ; higher probability of injury crashes. However, special sections such as curves and bridges were also included in the ; dataset considered in this analysis, making it impossible to make a direct comparison with the other sections.
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• Format:
  PDF
• Funding:
  C1625
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/17096/dot_17096_DS1.pdf
• File Type:
  [PDF - 3.99 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:5dd9af06e98f0f7137524f9ac9816ea0b8fcfb4aa76ade8aea07025871c54965