Ada County Highway District

ACHD's Road Wizard Sunday, October 15, 2017 ACHD's Road Wizard

Street closure sign declares impossible intersections on 10th Street in Downtown Boise; right-turn green arrow signal requested on westbound Chinden Boulevard onto Glenwood Street; "Do Not Block Intersection" sign and markings requested on State Street at Lemp Street

The Road Wizard Replies

Dear Road Wizard: There was a construction sign at 6th and State streets which said something like, "10th Street will be closed from 6th Street through 8th Street for crane work." Really? How does 10th cross 6th and 8th?


Road Wizard:

Two, four, 6th, 8th, what do we appreciate? Accurate construction work signs!

There were two road closures on or near State on back-to-back weekends in mid-September, and both projects used the same traffic control company. The first closure was on State between 6th and 8th for work at the Idaho State Capitol. The second was on 10th between State and Washington streets for work at another building.

Maybe the sign company neglected to change "6th through 8th" when they moved the closure to 10th. ACHD requires that road closures on public streets be posted seven days in advance (not including emergency situations) and ACHD inspectors watch for inaccuracies. But the impossible-intersections sign had already been removed before it could be corrected.

Dear Road Wizard: One of my pet peeves is the (sometimes blatant) inefficiency of our traffic signal system. There are a few small things that could help move traffic along. One specifically is heading westbound on Chinden Boulevard to turn right onto Glenwood Street. A green arrow here would help so every right-turning car doesn't have to stop at a red light when left-turning traffic is turning eastbound from Glenwood onto Chinden.


Road Wizard:

That's exactly how a "right-turn overlap" works. A green arrow is displayed for right-turning traffic while non-conflicting left-turning traffic also has a green arrow light.

It may seem that right-turn overlaps are an easy crowd pleaser that can be installed just about anywhere. But there are several factors to consider.

One such consideration is whether the right-turn green arrow will actually be an overall benefit to traffic flow. The amount of simultaneous, non-conflicting left-turning traffic has to be enough to make use of the overlap. If there aren't many left turns, the length of the right-turn green arrow would be too short to be of much use, especially when drivers can still make the right turn after stopping at the red light.

ACHD will investigate the possibility of a right-turn overlap at Chinden and Glenwood. ACHD manages all of the traffic signals in Ada County, but this intersection belongs to the state, so the Idaho Transportation Department would have to agree to any changes.

Dear Road Wizard: I really enjoy using Whitewater Park Boulevard on my way to work. My problem is that on the way home, after taking Whitewater Park and heading east on State Street, I have a terrible time turning left onto Lemp Street. The westbound evening traffic always blocks the intersection to make the turn at Lowell Elementary School. Is there a possibility of marking a box on the road and putting up a sign asking drivers not to block the intersection?

Road Wizard:

Of course it's already illegal under Idaho and Boise City codes to block intersections. Supplemental street paint and signs are typically used where there are frequent violations.

ACHD found that the illegal intersection intrusions on State at Lemp were isolated to peak evening commute times, and most drivers behaved decently. That isn't enough of a problem to trigger the need for a "do not block intersection" reminder.

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