Denver’s plan for a bus rapid transit line down Colfax Avenue has faced a common knock: Because of limitations including dedicated bus lanes that would be active only during the rush hours, it isn’t really true BRT.

But a major shift now under consideration — to make previously proposed rush-hour bus lanes along the sides into permanent, center-running busways through east Denver — would elevate the prominence of the high-frequency bus line.

The design, if adopted this fall as the preferred option, would come closer to fulfilling the BRT criteria promoted by transit advocates as making bus lines operate as quickly and as frequently as street cars, but at a fraction of the expense.

The still-unfunded project would beef up bus service between the Auraria campus and Interstate 225 in Aurora, with the center-running bus lanes traversing more than five miles between Broadway and near Denver’s city limit at Yosemite Street. Aurora is a project partner but has resisted dedicated bus lanes, though Aurora riders could see some BRT trappings such as quicker, more frequent service.

“Obviously, now that this new alternative has a dedicated lane 24 hours (a day), it definitely qualifies as true BRT,” said Ryan Billings, a senior city planner in the Department of Public Works who is the project manager. “I would call the section from Yosemite through Aurora ‘enhanced bus.’ It has all the bells and whistles, except for the exclusive lanes.”

Denver transportation planners unveiled the new alternative Tuesday evening to a project task force of neighborhood and mobility advocates.

How the new bus line would work

At each of 15 center-lane stops through east Denver, riders would wait on a pedestrian island in the street, pay bus fare at a kiosk and board quickly at curb level when the bus arrives. During the busiest periods, buses would run every 3 to 5 minutes — or more frequently, depending on demand — and buses would get priority at traffic signals to move through more quickly.

West of Civic Center Station and east of Yosemite, the new line’s buses would stop in the right lanes at official stops while the rest of the setup would be similar. In Aurora, riders might have a choice between rapid-transit buses and local buses that make more frequent stops.

In coming months, the city will seek input and evaluate the center-running option against the side-running-lanes design and a no-change alternative. Planners could propose a preferred option in September or October, Billings said.

One open question is the impact on cost. Billings said the center-lane pivot could add 25 percent, or roughly $30 million, to the bus rapid transit plan’s cost. The previous plan has been estimated at $125 million to $135 million. But the center-lanes design likely would operate better overall than the side-lanes setup, he said.

The soonest construction could begin, Billings said, would be in 2020, if the city nails down enough money from this fall’s bond package and federal sources the city plans to seek. The first parts of the system would open in 2021 under that timeline.

Task force members were generally enthusiastic Tuesday about the center-running design — though a few concerns about trade-offs linger, including what the effective elimination of the Regional Transportation District’s local route 15 through east Denver would mean for disabled riders.

Together, the 15 and the limited-stop 15L route make up RTD’s busiest corridor, carrying 22,000 riders a day.

Planners project a BRT ridership of 50,000 a day by 2035. Bus travel times are projected to be up to 15 minutes faster in peak periods compared to estimates of travel in the increasingly choked corridor if nothing is done.

Reversal of earlier design decision

The new design marks the revival of an idea that Denver planners initially had dismissed in early 2016, over the objections of some transit advocates who considered center-running lanes a better idea. Several successful BRT lines, including the HealthLine in Cleveland, use that model.

Planners based the decision at the time on the limited street space on parts of Colfax and a judgment that it was politically unpalatable to convert two of the four through-traffic lanes to bus-only all the time.

But Billings and other transportation advocates say Denverites’ attitudes toward transit — and demand for more options to fill transit gaps — are quickly changing the calculus. After the last large public meeting on the project in January 2016, community members pushed back against the side-running, limited transit lanes design.

That resulted in a fresh look over the last year.

“This alternative with a center-running lane is a vast improvement over the side-running lane,” said Joel Noble, a task force member representing Inter-Neighborhood Cooperation, an umbrella group for neighborhood organizations.

He urged careful refinement of the design to price efficiency: “Please examine if you need all those stops. If you do this right, people will want to replicate this all over the city.”

Center design presents potential trade-offs

But Michelle Reichmuth, a South City Park resident, voiced concern about the potential loss of local service through east Denver.

While planners project that most of Route 15’s local riders would be willing to walk up to a quarter-mile to the new line’s designated stops because it would provide speedier, more reliable service, Billings acknowledged that the drawback was among some that would have to be worked out.

At the same time, the center design addresses some pitfalls of the side-running setup, including cars trying to access street parking from the bus lane.

City projections have predicted the new bus line would increase the Colfax corridor’s capacity for transporting people in 2035, via both bus and car, by nearly 26 percent, after shifting more people to transit.

There are still big questions facing the proposal, including whether concern by drivers and neighborhoods about losing traffic lanes — a sentiment voiced at the January 2016 meeting — will embrace the center-running design.

And then there is the question of how to pay for it. Federal transit funding is an unsure bet, but $55 million for the Colfax project is included in the current project list for the city’s proposed $937 million bond package that’s being prepared for voters in the Nov. 7 election.