A multibillion-dollar overhaul of Union Station would boost capacity for rail and expand retail options as planners envision how the rail hub should function in 20 years.

A federal agency is taking a second look at the plans amid criticism it was too focused on cars, but in a clash with city planning officials, leaders of the bus industry are voicing their own concerns: They say growth in their mode of transportation is missing from the vision.

Plans for a slimmed-down bus deck have caught the attention of the industry, which argues the Federal Railroad Administration proposal is flawed in accommodating intercity and charter bus operations. They point to plans that could downsize bus space by as much as 72 percent at a time when other large cities are expanding the role of buses.

Supporters of the downsized proposal say less space dedicated to buses will increase efficiency. Meanwhile, bus advocates are urging the FRA and the project’s proponents — Amtrak and the Union Station Redevelopment Corporation — to rethink the proposal and restore space for buses, which are disproportionately used by lower-income riders.

“They haven’t quite left the bus out, but they’ve come close,” said Peter J. Pantuso, president and chief executive of the American Bus Association.

Amtrak, one of two sponsors of the project, hasn’t expressed a preference on the number of bus slips, and it wasn’t clear whether the FRA might take another look at the proposal.

The expansion of Union Station — a $10 billion private and public investment — envisions a transformation by 2040 that includes new concourses and tracks while broadening retail options. It could be years, if not a decade, before construction begins.

A preliminary design by the FRA calls for a two-level bus facility adjacent to the train hall with up to 40 bus slips, down from the current 61 bus spaces. Other options under consideration could bring the number of bus slips down to 17.

Inadequate bus capacity at the region’s largest transit hub could force bus operations back to scattered locations curbside, a system the city sought to change a decade ago, industry officials said. It also would put bus riders — many of them low-income and people of color — at a disadvantage, making connections to other transit and the amenities at Union Station more difficult.

Proponents of a smaller bus facility say the goal is to better use valuable real estate. The station, they say, should not be used for long-term parking, but instead to allow buses to go in and out as quickly as possible, which would allow for more trips.

“If a bus slip is sitting empty, or if a bus is parked for hours and hours and hours, then that means we’re not using [the space] very well,” said D.C. Council member Charles Allen (D-Ward 6), whose district includes Union Station.

Allen, who favors a smaller bus deck, said the current bus facility is not used efficiently and designating the same space at a revamped Union Station can’t be justified. He said the number of bus spaces should be between 20 and 40.

“I want that number to be as low as it can be but I am more interested in how we efficiently move the buses in and out,” Allen said.

An FRA analysis conducted in response to calls for a scaled-down bus structure concluded that 25 slips would be adequate to meet higher demand in 2040, assuming shorter turnaround times for tour and intercity buses. The project’s proponents initially had estimated at least 47 slips would be needed for peak bus demand, but the FRA lowered that number last year to the current 40-slip proposal, saying space could be shared with ride-hailing services.

Concerns about the size of the bus facility come as the FRA has temporarily halted its analysis of the Union Station redevelopment to revise key aspects of the project. Chief among them is a parking garage that critics say is too large and keeps the station too focused on cars.

City leaders have pressured the federal agency to downsize the proposed six-level, 1,600-space parking facility to be built above the bus deck. The FRA is working to amend the plan, including looking at potentially moving parking below ground. The agency is also likely to review the bus deck plan.

While the bus industry tries to retain the current bus space, it also faces opposition. The D.C. Historic Preservation Office within the city’s Office of Planning supports reducing the number of bus slips to 25, calling on the federal agency in a letter to “eliminate the unnecessary slips and promote better bus management practices.”

Developer Akridge, which is planning a $2 billion project that would add up to a dozen buildings along 14 acres of air rights above the train tracks, has lobbied for an even smaller bus deck with 18 slips.

Greg Cohen, a Greyhound spokesman, said the project offers an opportunity to give buses — and their riders — an essential piece of the transportation network at the nation’s second-largest rail hub. The project, he said, should consider projected growth in bus ridership and the need for affordable travel options.

Greyhound, one of the largest operators of intercity buses at Union Station, has asked the FRA to consider maintaining or even expanding the bus deck’s 61 slips.

Intercity bus travel has increased significantly in the past two decades, particularly between the District and New York. The number of scheduled daily trips operating between the two cities increased from 53 to 169, according to a study by DePaul University researchers. Industry leaders say they expect demand, which has plummeted during the coronavirus pandemic, to pick up.

As the District looks to downsize its bus terminal, other major cities in the Northeast are planning expansions, critics say. Plans at Boston’s South Station call for a 50 percent increase in bus capacity. The Port Authority of New York and New Jersey announced last month an ambitious plan to rebuild the terminal to create a modern bus station with greater capacity.

In Washington, Union Station opened its parking deck in 2012 to serve as a hub for intercity and charter buses. The transition, which happened after years of negotiations, was critical to getting most buses into a central space, and from picking up passengers at scattered curbside locations in the city.

At the time, U.S. transportation deputy secretary John Porcari said the agreement between the Union Station Redevelopment Corporation and bus companies, including Greyhound, Bolt Bus, Megabus and Washington Deluxe, was a step toward making Union Station into a intermodal transportation hub.

“By moving intercity buses to Union Station, we can increase tourism, provide more transportation options to D.C. residents, and help keep bus drivers rested and ready for the road,” Porcari said at the time. “This is a win for bus companies, a win for Union Station and a win for the residents of the District.”

The bus deck, on the first level of the station’s parking garage, is used by intercity, tour and charter, and DC Circulator buses. It has a small shop, restrooms and a waiting area.

According to an FRA report, about half of the available bus spaces are permanently reserved for intercity, tour and shuttle bus providers. D.C. Circulator uses five slips, and 18 are available for hourly and daily use and rental.

“The existing facility can accommodate current intercity bus demand, although passenger flows and queuing areas are cramped,” according to the FRA’s draft environmental impact statement last summer. “The bus facility is not adequate for forecasted 2040 needs.”

Intercity service at Union Station is expected to grow nearly 20 percent by 2040, while tour bus operations are expected to expand by 51 percent, according to the FRA.

While the most popular bus trips are between Washington and New York, buses take passengers between the nation’s capital and cities as far as Las Vegas and Miami, and to many cities and rural communities in between.

“What needs to be understood is the consequence of not providing enough capacity, because that means buses will be on the streets and in the neighborhoods,” said Cohen, the Greyhound spokesman. He said 40 slips would be tight in two decades.

Sean Hughes, director of corporate affairs at Coach USA, one of the nation’s largest bus companies and the parent company of Megabus, echoed concerns about the lack of room for growth, as well as potential effects on passengers who benefit from the connectivity to Metro, Amtrak, bike-sharing programs and other facilities at the station.

“Some of our passengers may not be able to afford other modes of transportation,” he said.

While a bus trip to New York can cost less than $30, an Amtrak ticket generally costs $49 or more.

Industry leaders say not meeting the needs of bus passengers would be an attack on transportation access for lower-income residents and communities that depend on bus services for travel.

About 60 percent of Greyhound riders, for example, are people of color, according to a company survey, and one in three riders are Black. Seventy percent of Greyhound bus riders live in households that earn less than $50,000, while more than 40 percent earn below $25,000.

Amtrak and the Union Station Redevelopment Corporation — which manages and operates Union Station under a long-term lease from the FRA — are sponsoring the redevelopment project. Amtrak officials say they support keeping bus operations integrated into the overall station expansion plan but would not say how much space they think should be allocated for buses.

“We are looking for the bus facility to be as efficient as possible and as size appropriate as possible,” said Gretchen Kostura, Amtrak’s senior program manager at Union Station.

Del. Eleanor Holmes Norton (D), who led the effort a decade ago to get buses integrated into Union Station, said she supports having at least 40 bus slips at the station.

“What we’re trying to do is to make Union Station a place for all transportation,” she said. “Having buses there is critically important.”

Before the pandemic, intercity buses served about 2.4 million riders at Union Station, and charter buses carried another 2 million, according to data from the American Bus Association. By comparison, Amtrak ridership was 5.2 million at Union Station.

“There’s almost as many people traveling in and out of Union Station by bus as Amtrak moves, and yet the bus industry is looked at as the stepchild, at best, to Amtrak,” Pantuso said. “Whatever facility is built, needs to be on par with whatever else is at Union Station. And not treat [the bus] as a second-class mode of transportation.”