Rural Intersection SPFS – Slip Lanes and Seagulls

In New Zealand the majority of rural intersection fatal and serious crashes occur at rural priority T-intersections. While most intersections have a standard layout higher volume intersections often have alternative layouts that include auxiliary lanes and/or channelization. Two alternative intersection layouts are reviewed in this research: 'priority controlled seagull (channelized) intersections' and ‘intersections with slip lanes’. Seagull intersections are used on roads to reduce traffic delays. However, some do experience high crash rates. Slip lanes (left turn for left-hand drive and right turn for right-hand drive) allow turning traffic to move clear of the through traffic before decelerating. Although there is debate about the safety problems that occur at Seagull intersections and slip lanes there has been very little research to quantify the safety impact of different layouts. In this study, safety performance functions have been developed for standard rural T-intersections and the two alternative intersection layouts for the key crash types. A point of difference in the modelling is that a design index has been developed for road layout variables, rather than including each layout variable separately in the models, along with exposure and speed variables.

  • Supplemental Notes:
    • This paper was sponsored by TRB committee ANB25 Standing Committee on Highway Safety Performance.
  • Corporate Authors:

    Transportation Research Board

  • Authors:
    • Turner, Shane
    • Wood, Graham
    • Tate, Fergus
  • Conference:
  • Date: 2019


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; References; Tables;
  • Pagination: 12p

Subject/Index Terms

Filing Info

  • Accession Number: 01698343
  • Record Type: Publication
  • Report/Paper Numbers: 19-04086
  • Files: TRIS, TRB, ATRI
  • Created Date: Mar 1 2019 3:51PM