What comes around: Long-range plan could add nearly 200 roundabouts to Ada County

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Do you remember your first experience with a roundabout? Do you stop? Do you yield? Speed up? Slow down?

After rolling through a roundabout – or traffic circle – more than once, they get a little easier.

The Ada County Highway District’s (literal and figurative) roadmap includes nearly 200 roundabouts in future years.

Instead of a stop sign or traffic lights, roundabouts allow drivers to enter a circular roadway by yielding to traffic. Engineers tout a decrease in conflict points, slower speeds and even environmental benefits. The Insurance Institute for Highway Safety said roundabouts cut accidents by more than a third – with a 75% decrease in injury crashes, and a 90% cut in fatal crashes. The MythBusters even found cars move through an intersection faster with a roundabout.

Ada County roundabout
A roundabout in Boise’s Barber Valley at ParkCenter Blvd. and Warm Springs Ave. Photo: Don Day/BoiseDev file

The first significant roundabouts in the area actually popped up in Canyon County at Happy Valley Rd. and Amity Rd. in 2006. For now, the intersection treatments remain in limited areas, including the Barber Valley, two new circles near St. Luke’s and scattered around the county. ACHD’s highest-profile roundabout to date remade the complicated intersection of 36th St, Hill Rd. and Catalpa Dr. The so-called “dogbone” roundabout smoothed out the flow of traffic, cyclists and pedestrians in the area near Hillside Jr. High.

More to come

But you might see a lot more in the coming years. The highway district’s “Master Street Map” shows a total of 176 roundabouts in nearly every part of the area.

Natalie Shaver with ACHD cautions that doesn’t mean you’ll be going round and round at every intersection.

Each dot at an intersection indicates the location of a possible future roundabout. Orange indicates a single-lane roundabout. Yellow indicates multi-lane. Red indicates dual-lane. Blue shows a triple-lane roundabout. Via ACHD.

“This does not mean they will all be built,” she said. “These are just areas where they would work.”

The map shows possible new roundabouts along many routes that could see major expansion or rebuilding in future years. The southwest quadrant of the county, which currently has many farm roads could hold roundabouts every half mile or so. Roads like Cherry Ln. and Franklin Rd. could add multi-lane roundabouts in areas that will soon interface with the State of Idaho’s freeway-like Central Valley Expressway project that would run north-to-south near the county line.

In ACHD’s next fiscal year, the traffic circles will pop up at Victory Rd. and Locust Grove Rd., Amity Rd. and Maple Grove Rd., Linder Rd. and Floating Feather Rd. and a few other locations. A so-called “mini-roundabout” is planned for Rose Hill St. at Owyhee St. as part of bikeway improvements on the Boise Bench.

Shaver said a total of 44 roundabouts are included in ACHD’s Capital Improvements Plan – which is a 20-year planning document for road improvements in the county.

Planned roundabouts

Here’s a list of the roundabouts envisioned in the CIP (single-lane unless otherwise noted):

  1. Amity & Cloverdale – multi-lane
  2. Amity & Eagle – dual-lane
  3. Amity & Five Mile – multi-lane
  4. Amity & Linder
  5. Amity & Maple Grove
  6. Amity & Ten Mile
  7. Beacon Light & Ballantyne
  8. Beacon Light & Eagle – multi-lane
  9. Beacon Light & Linder – multi-lane
  10. Beacon Light & Palmer
  11. Beacon Light & Park
  12. Columbia & Cloverdale
  13. Columbia & Ten Mile
  14. Deer Flat & Ten Mile
  15. Floating Father & Ballantyne
  16. Floating Feather & Linder – multi-lane
  17. Floating Feather & Palmer
  18. Floating Feather & Park
  19. Floating Feather & Plummer
  20. Floating Feather & Star
  21. Franklin & McDermott
  22. Gowen & Orchard – multi-lane
  23. Hill & Horsehoe Bend – multi-lane
  24. Hill, Hill Parkway & Seaman Gulch
  25. Hubbard & Ten Mile
  26. Kuna & Cloverdale
  27. Lake Hazel & Black Cat
  28. Lake Hazel & Eisenman – dual-lane
  29. Lake Hazel & Five Mile – dual-lane
  30. Lake Hazel & Linder
  31. Lake Hazel & Locust Grove
  32. Lake Hazel & McDermott
  33. Hake Hazel & Orchard – dual-lane
  34. Lake Hazel & Pleasant Valley – dual-lane
  35. McMillan & Black Cat – multi-lane
  36. McMillan & Star – multi-lane
  37. Pleasant Valley & Orchard Extension- dual-lane
  38. Overland Rd. Extension & Black Cat
  39. Ustick & Black Cat – dual-lane
  40. Ustick & Star
  41. Victory & Black Cat
  42. Victory & Linder
  43. Victory & Locust Grove – multi-lane
  44. Victory & McDermott

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