This report contains a general description of roundabouts (design, location and traffic conditions) and a traffic safety study. The most notable result is that the injury consequence (number of injured persons per accident) is very low at roundabouts. The reason is that many types of accident with high injury rate do not occur or occur rarely at roundabouts. At a roundabout traffic flows at an oblique angle and not at right angles as at an ordinary junction. Conflicts where vehicles meet at an oblique angle and with a low relative speed result in slight injuries. At an ordinary junction conflicts involving a left hand turn are common and have severe consequences. These conflicts are rendered impossible at a roundabout and whether driving straight ahead or turning to the right or the left, all vehicles have to perform a right hand turn and eventually a weaving manoeuvre. However, many conflicts occur in entering the roundabout. Hesitation at the entrance results in many overtaking manoeuvres. Moreover, the frequency of single accidents increases, especially turning accidents and collisions with the roundabout island. Both these accident types have high injury consequences compared to other types of roundabout accidents. On the other hand the number of accidents occurring at roundabouts is not extremely low. The accident rate (the number of accidents per million entering vehicles) is approximately 0.6 for an ordinary roundabout. The variation is great and depends in the first place upon the number of access roads and the size of traffic flow. A conclusion is that roundabouts seem to be a type of junction with a very high level of traffic safety. (TRRL)


  • Swedish

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 33 p.
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00382440
  • Record Type: Publication
  • Source Agency: Swedish National Road and Transport Research Institute (VTI)
  • Report/Paper Numbers: Monograph
  • Files: ITRD, TRIS
  • Created Date: Apr 30 1984 12:00AM