I'll never understand why they made Boulder a one way street, it makes no sense.
The one-way traffic flow scheme was conceived in the 1940s, or perhaps even earlier, as quick access to the proposed expressway system.
The one-way streets worked in pairs. Boulder was paired with Cheyenne. The Boulder/Cheyenne idea was to provide a route to/from the Tisdale access ramps at Fairview St. Cheyenne also provided access to the east-bound on-ramp on the south leg of the IDL and on to the BA Expressway.
Cincinnati/Detroit provide access to the north leg and the southeast IDL interchange. 1st/2nd provide access on the east and west legs, as do 7th/8th.
The intersections are mostly 380 feet apart. By alternating the directions of the one-way streets pairs, traffic signals in the downtown core could be coordinated (most of the time) for relatively smooth traffic flow.
A two-way Boulder will need re-designed signals at 2nd, 7th, 8th, and 10th, at a minimum. 6th also probably has enough traffic to require a signal, maybe 3rd, too. But 4th and 5th? Stop signs on the those streets might work.
A two-way Cheyenne will need re-designed signals at 1st, 2nd, 7th, and 8th, at a minimum. 5th St is one-way west-bound at Cheyenne; 4th is one-way east-bound. Three stop signs would probably work at both of those intersections. 3rd & Cheyenne and 6th & Cheyenne don't seem to me to have much traffic, although I don't know what the counts are. The City could try 4-way stops at 3rd and at 6th, at least initially.
If the goal is to have smooth flow of vehicular traffic, then paired one-way
THROUGH streets with synchronized signals work well. But if it's not important for cars to be able to roar through the downtown without stopping, then a few more relatively cheap stop signs would probably work almost as well as very expensive signals. Many times, I've seen cars stopped at 3rd, 4th, 5th, and 6th, waiting for a light to turn green, without any cross traffic at all.
For pedestrian crossings, I think the one-way streets with the synchronized signals work the best.