There’s no timeline in the works for the proposed Red Rock Corridor busway through south Washington County.

The transitway, planners say, will happen when it actually proves to be a viable project with a strong base of transit users.

“It’s all based on hitting benchmarks for riders, instead of happening in a given year,” said Lyssa Leitner, Washington County transportation planner.

“We aren’t in the business of just implementing the project and crossing our fingers [that people use it]. We want to test the market. We plan to ramp up regular bus service to lay the foundation for implementing more of the BRT-type feel.”

The end goal is BRT, or bus rapid transit — frequent all-day service that replicates light-rail transit service, but at a much lower cost.

The corridor commission responsible for the project last week approved a plan that sets in place an exact route and plans for stations, as well as a process to reach the end goal.

The transit line is to take commuters from Hastings, in Dakota County, through south Washington County and on to Union Depot in downtown St. Paul, where the light-rail Green Line has a station.

Plans call for Red Rock stations in Hastings, Cottage Grove, St. Paul Park, Newport and the Battle Creek neighborhood of St. Paul, although studies show that the meat of the line’s usage would go from Cottage Grove northward.

The plan calls for enhanced conventional bus service with rides every half hour along the Hwy. 61 corridor as officials work with local communities to pump up the user base with more jobs and homes in the vicinity of the stations.

“We’re crossing our fingers on getting an all-day bus route” as part of a competition for grants in the metro area, Washington County Commissioner Karla Bigham told colleagues on the board this month.

“And then hopefully we get a comprehensive transportation bill [from the Legislature] so we can look at an express route from Hastings, stopping at Newport,” she added. “We look forward to good things to come in this corridor.”

There’s a specific trigger point: The plan calls for replacing a conventional, fairly frequent bus route — 363 — with an “interim BRT service” when the number of passengers rises to 25 persons per hour of active service.

But that’s not expected to happen until after 2020.

“This stuff doesn’t happen overnight,” said Washington County Commissioner Gary Kriesel. “You look long-term on these things.”

The first higher-density, transit-oriented housing near the Newport station — one big key to adding riders — is coming soon.

Red Rock Square is a $10 million, 42-unit affordable apartment complex on which construction is to begin this year, just west of the transit station.

Planners have learned to be cautious when it comes to predictions: There was talk in 2010 for instance of a commuter train for Red Rock, perhaps getting rolling by 2018.