Impact of rut depth and IRI on accidents

Urasyvyyden ja epatasaisuuden vaikutus onnettomuuksiin

The aim of the study was to find out how changes in rut depth affect the accident rate. Secondly, changes in the International Roughness Index (IRI) were also examined in two rut classes (deep and shallow ruts). In addition, the study examined whether a deep rut lowers the traffic flow rate more than a shallow rut. The study examines at one time the life cycle of one 100-metre stretch of road in the years 1990-2004 as regards rut depth, IRI and number of accidents. This means that rut depth and IRI are the most significant explanatory factors affecting any change in the number of accidents, since road geometry, frequency of junctions, and surrounding environment remain constant. The statistical practices regarding road accidents, the vehicle stock and observance of speed limits may, however, change during the life cycle. In order to allow for these differences, the material has been weighted in such a way that resurfacing during the life cycle and the related period of shallow rutting are considered to occur equally often at the beginning, middle and end of the life cycle. On examination of the calculated averages, it emerges that 1) in winter during a period of 6-10 mm rutting, the accident rate is on average 8% higher and when ruts are deeper than 10 mm, 22% lower than on the same road with less than 6 mm ruts. 2) in summer during a period of 6-10 mm rutting, the accident rate is on average 21% higher and when ruts are deeper than 10 mm, 4% lower than on the same road with less than 6 mm ruts. In summer and in winter, both 6-10 mm ruts and over 10 mm ruts lower the average speeds of passenger vehicles, vans and buses by the same amount - i.e. 0.3-2 km/h. This partly explains the fact that over 10 mm rutting may result in fewer accidents, although by the same logic, 6-10 mm rutting should also have reduced the number of accidents. The accident rate does not rise or fall according to a regular pattern if a deep rut is associated with higher than average IRI. This report may be found at http://alk.tiehallinto.fi/julkaisut/pdf2/3200961-v-urasyvyyden_ja_epatasvaikonnett.pdf

• Record URL:
  http://alk.tiehallinto.fi/julkaisut/pdf2/3200961-v-urasyvyyden_ja_epatasvaikonnett.pdf
• 
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/9789518035902
• Authors:
  • LEHTONEN, K
  • LAINE, V
  • JARVINEN, S
• Publication Date: 2005

Language

• Finnish

Media Info

• Pagination: 44p+app
• Serial:
  • TIEHALLINNON SELVITYKSIA, FINNRA REPORTS
  • Volume: 3200961
  • Issue Number: 49/2005
  • Publisher: Finnish Road Administration
  • ISSN: 1457-9871

Subject/Index Terms

• TRT Terms: Crash rates; Depth; Rutting; Traffic flow
• Uncontrolled Terms: Rut
• Geographic Terms: Finland
• ITRD Terms: 1612: Accident rate; 6499: Depth; 8035: Finland; 3081: Rutting (wheel); 671: Traffic flow
• Subject Areas: Design; Pavements; I22: Design of Pavements, Railways and Guideways;

Filing Info

• Accession Number: 01081635
• Record Type: Publication
• Source Agency: TRL
• ISBN: 978-951-803-590-2
• Files: ITRD
• Created Date: Nov 29 2007 12:54PM