Helena is holding to outdated regulations that do not apply to its unique layout, constricted by mountains. It routes east/west traffic on only a few streets to and from the west exit, Highway 12 West. It allows semis and belly dumps on residential streets. It should direct semi traffic that is not making delivery over arterials only.
These are observations, surmises, guesses.
Let Cedar and Main to Euclid carry commercial large truck traffic. Let Henderson carry the sand/construction.
Large truck right turning lanes at the top of Henderson. Left turning lanes at both ends.
Route Fort Harrison, emergency traffic to Henderson or Brady.
Peosta was built for through traffic. Two blocks of construction for a feeder off Henderson to Country Club Lane. Possibly make it a two-lane, one-way and pair it with Leslie or Wilder.
Let one-way street pairs north of Euclid funnel traffic through to Highway 12.
Build out near beginning of Franklin Mine road, to point at Fort Harrison where Birdseye turns west. A wide turning point for military and construction traffic coming from areas north of Franklin Mine.
An enormous amount of traffic gone from Green Meadow, McHugh, and Custer, on down the line.
Kathleen Curd Rau