Ada County Highway District

Amity Corridor Roundabout Study

General Description:

The Amity Corridor Study recommendations were adopted by ACHD Commissioners in January, 2008. The study evaluated six intersections from McDermott to Eagle Road along Amity as possible locations for roundabouts with the intent of improving traffic flow and safety. The study compared roundabouts versus traffic signals at each intersection to determine whether traffic control measures was warranted and which would be most effective.

Final Report

Project Purpose

Amity Road was chosen for this study for several reasons, one is because of its current rural nature, which provides space for potential roundabouts. The goal is to plan for future growth and to determine what traffic control measures, if any, would be the most effective in the Amity Road area. The Amity Corridor is used frequently as a parallel alternate access to Interstate 84. The use of roundabouts on this corridor would lend to consistency with the existing roundabout on Amity in Canyon County, would increase traffic flow and would improve safety.

Criteria for Roundabout Consideration

A list of criteria was used in assessing whether a roundabout would effectively work at each intersection. Among the criteria:

  • Right-of-way impacts
  • Crash data
  • Pedestrian use
  • Topography & grade
  • Traffic speed
  • Current & future traffic volumes


Monday, January 14, 2008
Commission to vote on study recommendations, 1.23.2008

Ada County Highway District (ACHD) staff will ask the ACHD Commission to adopt the findings of the Amity Corridor Roundabout Study. An evaluation of six intersections along Amity Road determined that four of the intersections should be considered for roundabouts. The following intersections will be recommended to the Commission as future roundabout locations along Amity Road: Linder, Ten Mile, Black Cat and McDermott. Ten Mile is currently scheduled for design in 2008 with construction anticipated for 2011. The remaining three intersections are scheduled for construction in the next 11- to -20 years.


Time Frame

Start Date:
End Date:

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