Ada County Highway District

ACHD's Road Wizard Sunday, May 27, 2018 ACHD's Road Wizard

Flashing yellow arrow signal disappears in the morning at low-traffic Roosevelt Street and Rose Hill; westbound traffic lines up on Hill Road at Collister Drive due to a four-way stop and efficient "dog bone" roundabout; Cloverdale Road and Desert Avenue intersection not a candidate for a temporary signal during the Lake Hazel/Cole intersection construction.

The Road Wizard Replies

Dear Road Wizard: I noticed on my morning commute around 8:30 a.m., driving towards downtown on Roosevelt Street, at the signal at Rose Hill, that the left turn never gets a flashing yellow arrow. It appears to happen in both directions. I have seen a flashing yellow at different times of day though. I have seen this behavior on congested streets during peak hours against peak through traffic, which makes sense. But Roosevelt is just one lane in each direction, with a 30 mph speed limit and relatively light traffic. Is this a mistake or intentional?


Road Wizard:

The yellow arrow disappears in a flash to improve safety for children during the get-to-school dash.

Flashing yellow arrows allow drivers to make left turns during breaks in oncoming through traffic. As they make the left turn, drivers must yield to that traffic as well as any pedestrians using the crosswalk.

This double-duty situation for motorists should be avoided when young, inexperienced pedestrians are using the crosswalk before and after school. Roosevelt and Rose Hill is one of many intersections that pause the flashing yellow arrow and display just the green arrow left-turn signals during times when children are present.

Dear Road Wizard: With the Hill Road parking issue just west of the "dog bone" roundabout at 36th Street addressed (thank you for the conversion to parallel parking), an additional request for Hill is this: the roundabout is so good at siphoning traffic westbound at the end of the work day, that those cars are now stacked up on Hill at Collister Drive. This is unfortunately due to the four-way stop at Collister. It is a traffic hazard for cars and bicyclists. Any consideration to a solution such as a timed signal there?


Road Wizard:

There is also extra traffic on westbound Hill during the evening commute at the moment because people are using it as an alternative route to avoid the road construction at the State Street/Veterans Memorial Parkway/36th Street intersection.

ACHD realizes something will need to be done to better move traffic through Collister eventually, but this is likely to happen several years from now. All-way stop intersections are actually considered relatively safe because traffic is slowed down. But bicyclists on Hill still have to be cautious while approaching the stop sign and taking their turns in the intersection.

Dear Road Wizard: Traveling Maple Grove between Amity and Lake Hazel roads is especially busy with the closure of the Lake Hazel/Cole intersection. The four-way stop at Desert Avenue really causes backups during commutes. Has there been discussion about a signal at that intersection, even temporarily, while Lake Hazel/Cole is completed?


Road Wizard:

Temporary signals are sometimes used near construction zones when they will be a true benefit. But there wouldn't be much improvement at Maple Grove and Desert because the intersection doesn't have left-turn lanes.

Left-turn lanes at signals allow multiple travel directions to have green lights at the same time, such as opposing left-turning drivers. Maple Grove and Desert has only one lane for each intersection approach, so turning and through traffic must share lanes. The signal could only display a green light for one travel direction at a time while everyone else waited. That wouldn't provide enough of an efficiency gain to justify the expense of building a temporary signal.

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