Ada County Highway District

ACHD's Road Wizard Sunday, January 29, 2018 ACHD's Road Wizard

What determines the decision to construct four-lane or two-lane roads -- Parkcenter Boulevard verses Ten Mile Road? Franklin Road west of Ten Mile Road to Black Cat Road now has more lanes but no higher speed limit.

The Road Wizard Replies

Dear Road Wizard: What determines the decision to construct four-lane roads versus two lanes? In undeveloped areas like east of the Boise River for Parkcenter Boulevard there is a four-lane road, but in the west, like Ten Mile Road, there are only two lanes. West Ada County roads are clogged due to development and then taxpayers have to pay for haphazard widening, rather than charging developers to widen the road before building to accommodate increased traffic.


Road Wizard:

Parkcenter was a developer-driven project in the early 1980s. The road originally stretched from Beacon Street to around Apple Street, and was funded through a "local improvement district" (LID). An LID collects fees from certain property owners/developers who have agreed to repay the cost of a specific road project.

Ten Mile as a two-lane road goes back to the early days of the Treasure Valley. Like Parkcenter, developers have been charged to help cover the cost of road improvements on Ten Mile. The difference is that the money is now collected through impact fees, rather than an LID. About $3,000 is charged for each new house.

While LID revenue goes toward a specific project, impact fees are spent wherever road improvement priorities are highest. The decision regarding when to widen a road is based on many factors, including traffic congestion and funding. Input from each city, along with Ada County, is also considered.

The way impact fees are distributed could mean that street widening may occur before development, such as with Ten Mile from Overland Road to Franklin Road. Other times this happens after some or most of development is complete, such as on Ten Mile from Ustick Road to Chinden Boulevard. Planning for widening that particular section has already begun.

Dear Road Wizard: ACHD was kind enough to widen Franklin Road west of Ten Mile Road to Black Cat Road, adding three more lanes! The road is great but now the speed limit has been reduced to 40 mph. That seems a little slow considering it used to be 45 mph with just two lanes. Can we get that bumped back up?


Road Wizard:

Back during the planning for widening Franklin from Ten Mile to Black Cat, the speed limit on Franklin east of Ten Mile to Linder Road was 40 mph. Some law enforcement agencies prefer consistent speed limits along a corridor, so ACHD set most of Franklin through the city of Meridian at 40 mph.

However, speed studies later revealed that 45 mph was more appropriate for Franklin between Ten Mile and Linder, so that section went up to 45 mph. Franklin west of Linder to Black Cat remained the same with plans to look at the speed limit after the widening work was finished. That's pretty typical after a major change to a major roadway.

The Meridian Transportation Commission, which makes recommendations to the Meridian City Council, also requested a speed limit analysis on Franklin through the city limits. ACHD is doing speed studies and will present those findings to the commission in February before making any changes.

It's not unusual for speed limits to change after major roadway construction. After the Ten Mile Interchange opening, Ten Mile from Franklin to Interstate 84 was originally set at 35 mph. But it was later increased to 40 mph before finally getting bumped up to its current 45 mph limit.

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