Ada County Highway District

ACHD's Road Wizard Sunday, July 24, 2016 ACHD's Road Wizard

"No left turn" sign on Glenwood Street at Mountain View Drive installed because of grandfathered berm; safety concerns remain about a flashing yellow arrow at Parkcenter Boulevard and Apple Street

The Road Wizard Replies

Glenwood Street at Mountain View Drive. Because of this change (which feels like a knee-jerk response to the fight going on with property owners at that corner), there is now limited access out of the subdivision. Coffey Street is narrow, has no lane paint, isn't maintained during the winter, weed covered, and hardly a reasonable access for the amount of traffic it now has to endure. I used to turn left onto Glenwood without a problem. This winter, I will have to travel to Maple Grove Road to get to Chinden Boulevard. What was the logic of restricting this access for such a large neighborhood?

Road Wizard:

At stop signs like the one on Mountain View Drive, another type of view is important. The ability for drivers to see oncoming vehicles is required by state law, and is measured by a "vision triangle" that must be clear of obstructions. However, Idaho's requirements don't address all sight distance concerns.

Local governments are allowed to create more demanding requirements than what exists at the state level. ACHD changed its sight distance ordinance in 2012 to include rules to prevent property owners and others from creating sight obstructions on private property.

So what we have is a landscaped berm at the corner of Mountain View and Glenwood that met the old guidelines but doesn't meet the new ones. However, the berm is on private property and was created prior to the policy change, so there's no legal standing to force its removal.

The other way to make the intersection compliant was to forbid the left turn from Mountain View onto Glenwood.

An average of only three drivers per hour were counted making that turn, and often doing so by taking risks. Nearby Coffey Street can handle those extra motorists, but please use Maple Grove on slick mornings.

Dear Road Wizard: I wrote to you awhile ago about putting a flashing yellow arrow in the westbound left-turn lane on Parkcenter Boulevard at Apple Street. I would like to have you look at the intersection again because the current operating program seems out of touch. The eastbound traffic for most of the day is light. I have sat through the red arrow many times with no traffic coming toward me. There is more than adequate time to make a safe turn even when cars travel above the speed limit. Please reconsider!

Road Wizard:

There are still no plans for a flashing yellow arrow left-turn signal because of safety concerns. Parkcenter curves as it approaches Apple, and that, along with the tree-lined median island, can inhibit judgment of oncoming driver speeds.

Every other possible technique has been used to minimize left-turn delays, however.

The traffic signal is often in "free mode," including during weekday mid-mornings and mid-afternoons. The left-turn signal activation is based on vehicle detection. That means the signal isn't waiting for pre-timed, coordinated through-traffic green lights to wrap up before serving the left turn.

Still, there's enough traffic on Parkcenter to benefit from operating in "coordinated" at Apple between 11:30 a.m. and 1:30 p.m. That's when the yellow arrow would be especially helpful. Instead, the left turn is programmed to give drivers a green arrow two or even three times in the same signal cycle.

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