One week it might be a doctor’s appointment. Another week, it might be choir practice. For Ty Bush, something usually has to give as the 49-year-old disabled woman struggles to cover the rising cost of getting around.

“I have to make that choice,” said Bush, who lives in Prince George’s County and tries to manage on her monthly income of $913.

That’s become a lot harder, she said, since Metro changed its fare policy last year for MetroAccess, a transit alternative for the elderly and disabled.

A round trip from Bush’s Suitland home to her spinal-cord specialist in Rockville is $14. The cost to her church on St. Barnabas Road, about three miles from her home, varies from $3.40 to $7 each way, depending on the time and day of the trip.

Two years ago, every trip she took, wherever she was going, cost her $3.

Now, Metro charges based on a formula that takes into account the distance, time of travel and the fastest way to take the trip on bus and rail. It is part of Metro’s strategy to address rising costs and increasing demand for the service.

That fare structure, which results in multiple possible fares, has created a lot of confusion and uncertainty for people who depend on the service and are living on fixed incomes.

Riders and disability advocates have complained for months about the fares, which, according to Metro, range from $2 to $7 per trip. Advocates say they are concerned about both the unpredictable fares and the overall jump in cost.

“We don’t like the fares. We don’t understand them,” said Regina Lee, a member of Metro’s Accessibility Advisory Committee and an advocate with the nonprofit Independence Now. “People are struggling to get to work now, and they can’t do any extracurricular activities because the fares are so high.”

In response, Metro is trying to develop a fare calculator that would let customers determine what fare they would pay at a given time of day and would allow them to shop for the lowest fare when making a reservation.

Metro says fares can be simple to calculate when the trip corresponds to a direct bus or Metro route. For example, a MetroAccess trip from Columbia Heights to Gallery Place would be $3.40, or two times the $1.70 fare for the non-rush-hour Green Line ride.

But many trips are more complex, and the planned calculator is far from done.

Rising demand

The current structure was put in place as part of an effort to better manage the rising costs of the service, and Metro officials say it complies with Americans With Disabilities Act requirements.

Ridership and costs have rapidly increased since MetroAccess launched in 1994. In the past five years, the cost to operate the service has doubled. MetroAccess transported 2.5 million passengers in fiscal 2012 at a cost of $116 million, up from 1.6 million passengers in fiscal 2007 at a cost of $57.7 million.

“We certainly understand that any fare increase is going to be difficult,” said Christian T. Kent, assistant general manager of access services at Metro. “We have been able to provide the same amount of service to customers even with the rising cost. The fare increase . . . was designed to ask the customers to contribute just a little more to the overall cost.”

It costs Metro an average of $50 to provide a MetroAccess ride, compared to $3 to $4 a passenger to run bus and rail. That makes the service heavily dependent on subsidies.

Metro officials said under the former fixed-rate system, passenger fees covered only about 5 percent of the MetroAccess budget. Customers paid $2.50 per trip from 2005 to 2010 and $3 from 2010 until the current fare structure took effect in February 2011.

As part of its strategy to reduce MetroAccess costs, Metro has been encouraging users to choose bus and rail instead. The transit agency now offers MetroAccess customers free bus and rail service, as well as information on how to navigate the bus and rail systems.

Across the country, other transit agencies are grappling with similar problems. In the face of budgetary challenges, many have turned to service cuts or fare increases, according to a survey by the American Public Transportation Association last year.

“We have a growing population of people who are into the senior years and a growing population of persons with various forms of disabilities,” said Greg Hull, director for security and operation support for the association. “Consequently the demand and need for specialized transit services is increasing steadily.

“So we have a bit of a dilemma where quite simply the transit agencies are hard pressed to meet the demand,” he said.

Confusing prices

Phil Posner, a member of Metro’s Accessibility Advisory Committee, said that users generally understand the need for a modest increase but that for most, it remains difficult to understand why they might be charged $7 to go someplace and $3.20 to return, while using the same route.

“A good portion of the riders are missing least expensive fares by one or two minutes just because they can’t calculate it,” Posner told Metro board members last month.

Hazel Lyons, a Northwest Washington resident who uses MetroAccess daily to get to her Department of Labor office downtown, said she pays $7 in the morning to get to work and $6 in the evening to get home. She said she was used to paying $2.50 each way.

“I have a problem with the formula,” Lyons said. “From $2.50 to $7 is a lot of money.”

About a quarter of MetroAccess users pay the maximum fare of $7 and roughly half of the customers pay $3.20, according to Metro.

Disability advocates say the fare calculator Metro is developing would be helpful to customers by giving them the option to see all rates within a 30-minute window.

But the calculator is not expected to become available until around May, Kent said. He said technical development of the tool is very complex. When it was tested a few months ago, it overloaded the system.

Advocates are asking Metro to find an interim solution. They also say the calculator should be accessible to customers who don’t book their trips on the Internet. Only 3 percent of MetroAccess customers usually make their reservations online, according to Metro.

Bush, who became fully disabled 10 years ago after an accident left her spine injured, said that when she really needs to go to one of her regular checkups and can’t find the $7 for the one-way trip, she takes bus and rail. But she said her body — with a back brace, batteries in her back and a morphine pump in her stomach — is sensitive to motion and any bumps in the road or the rough Metrorail stops cause her pain.

“At least with MetroAccess, I can tell the driver to slow down,” Bush said. “It is difficult. I still got to pay rent. I still have bills to pay.”