Geometric Design and Other Characteristics Affecting Operating Speeds On Gravel Roads

In the United States, there are nearly 1.6 million miles of unpaved roads, which approximately represent about 53% of all roads and consist mainly of gravel roads. Even though such gravel roads carry low volumes, they provide an invaluable service to the mobility and transportation needs of people living in rural areas. Operating speed on the other hand is extremely important for any type of a roadway. Even though speed limits of gravel roads are typically set based on statutory guidelines there are some instances where exceptions are in place. Other characteristics of gravel roads also vary significantly across gravel roads. Accordingly, the objective of this study was to evaluate various factors affecting the operating speeds on gravel roads. Field speed data were collected at number of sites located in the state of Kansas using automatic traffic data counters. Based on the speed data collected, comparisons were made based on various characteristics and simple linear regression models were developed to predict 85th speed and the mean speed of vehicles on gravel roads. The factors looked into and evaluated in this study include surface type, roadway width, speed limit, and percentage of heavy vehicles. Results of this study indicated that the 85th percentile speeds on gravel roads are affected by surface type, road width, and the percentage of heavy vehicles. Interestingly the speed limit was not a predictor of the operating speeds on gravel roads. Lowered posted speed limit values on gravel roads have also not helped in reducing operating speeds, but have increased the number and percentage of speed limit violators.

• Corporate Authors:

  Polytechnic University of Valencia

  Department of Transportation, Camino de Vera
  Valencia,   Spain  46022
• Authors:
  • Dissanayake, Sunanda
  • Liu, Litao
• Conference:
  • 4th International Symposium on Highway Geometric Design
  • Location: Valencia , Spain
  • Date: 2010-6-2 to 2010-6-5
• Publication Date: 2010

Language

• English

Media Info

• Media Type: CD-ROM
• Features: Figures; References; Tables;
• Pagination: 12p
• Monograph Title: 4th International Symposium on Highway Geometric Design, June 2-5, 2010, Valencia, Spain

Subject/Index Terms

• TRT Terms: 85th percentile speed; Geometric design; Gravel roads; Heavy vehicles; Operating speed; Speed limits; Width
• Uncontrolled Terms: Surface types (Pavements)
• Geographic Terms: Kansas; United States
• Subject Areas: Design; Highways; I20: Design and Planning of Transport Infrastructure;

Filing Info

• Accession Number: 01338155
• Record Type: Publication
• Files: TRIS
• Created Date: Apr 28 2011 1:01PM