Ada County Highway District

ACHD's Road Wizard Sunday, August 12, 2018 ACHD's Road Wizard

Reasons why manhole covers aren't always level with the road surface; "dogbone" roundabout on Hill Road kicking congestion can down the street, says reader; 16th Street and Hays intersection signal operates in its own world.

The Road Wizard Replies

Dear Road Wizard: Why can't the manhole covers be level with the blacktop? On Cherry Lane before Linder Road for example they feel like they are potholes.


Road Wizard:

When roads are new, manhole covers are flush with the surrounding surface. In many cases, concrete rings, or "collars", are poured around manholes to provide a strong, supportive transition to the asphalt.

But even manholes with collars can settle over time, especially when they are directly in the wheel path of vehicles. Metal rings on manholes can also flatten out, and chip seal applications may raise the road surface around manholes, giving them pothole-type qualities.

Drivers don't have to always bump and bear it, however. ACHD consistently works on problem areas by removing the concrete collars, and then pouring fresh, level concrete. Unfortunately, this also comes at a cost of around $1,000 per manhole.

Dear Road Wizard: Well the great "dogbone" roundabout constructed at 36th Street and Hill Road has kicked the congestion can down the road to the east. Traffic flow at peak periods leaves little opportunity for residents east of 36th to merge onto Hill Road from their subdivisions. Traffic going north on 28th Street to Hill now backs up waiting for an opportunity to turn west on Hill. The light at Harrison Boulevard backs up morning traffic at least a half mile. Anyone looking into the possibility of installing a traffic signal at 28th and Hill to reinstate some control over the flow?


Road Wizard:

No good deed goes "uncongested", right? The new roundabout sends a more random stream of traffic down Hill Road, which is different than how traffic approached from the old signalized intersection. In the past, traffic coming from the signal tended to flow in clusters, which offered better opportunities for drivers turning onto Hill.

But at least some of the trouble is being caused by an entirely different intersection. The big State Street/Veterans Memorial Parkway/36th Street rebuild has changed traffic patterns in the area, and some drivers are using Hill as an alternative east/west route.

This level of congestion isn't necessarily standard for Cherry at Linder. Utility work being done prior to the widening of Franklin Road has closed the section between Black Cat and McDermott roads, and Ustick Road widening work is underway. Drivers are using Cherry as an alternate route.

Improving and maintaining State as the primary east/west route means that the number of people using Hill may decrease in the future. It's best to see how that all works out before seriously considering a new traffic signal at 28th/Hill.

Dear Road Wizard: When traveling on Hays Street, I always get a red light at 15th Street. As I wait, the left-turn light at 16th turns green and back to red before my light at 15th turns green. I always miss the left-turn light! Is it possible to hold the left-turn light green for a little longer?

Waiting in the North End

Road Wizard:

While nearly all signalized intersections in the downtown Boise traffic grid are coordinated, 16th and Hays is not.

To ensure optimal traffic flow, it's important to allow two turning movements to happen at the same time - drivers turning right onto southbound 16th from Hays and drivers turning left onto southbound 16th from Hays. This has to be carefully planned so pedestrian crosswalk times are not impacted.

As a result, there isn't much wiggle room for a longer left-turn light, and the signal can't easily be coordinated with other signals, including 15th. Even if the left-turn light at 16th was green for a bit longer, it would still work independently, so the benefit would be minimal.

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