The growth of an urban area typically extends outward along arterial highways. The nature of the land use along the highways gradually changes from rural and agricultural use to suburban use with strip commercial developments. The resulting growth in traffic volume and frequent turning movements cause congestion and increased accident experience, which necessitates widening the existing two-lane highways to four or more lanes. Under current design guidelines, urban roadways must have a minimum clear zone width of 0.46 m (18 in.) beyond the face of the curb. On the other hand, high-speed rural arterial highways typically require a clear zone width of 9.1 m (30 ft) or more beyond the edge of the travelway. Some intermediate design requirements of clear zone width are needed for this transitional type of suburban, high-speed, curb-and-gutter roadway. Furthermore, the widening of the highway reduces the available clear zone width unless additional right-of-way is purchased. In other words, when the highway is widened the typical clear zone width of 9.1 m (30 ft) common to rural highways may be needed to provide more travel lanes. This paper presents the results of a study to determine an appropriate and cost beneficial clear zone requirement for such suburban, high-speed, arterial highways in an upgrading or reconstruction situation.


  • English

Media Info

  • Features: Photos; References; Tables;
  • Pagination: p. 119-126
  • Monograph Title: Geometric design, roadside safety features, roadside hardware monitoring, and scenic loop tours
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00714998
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Dec 26 1995 12:00AM