Advocates for people with disabilities say Metro’s plans to make SmarTrip cards more accessible to riders by installing new vending machines at every rail station fall short in one crucial area: The new machines are not expected to be immediately accessible to all people with limited vision.

The machines, which are scheduled to make their debut Sept. 1, have no audio feature. Riders who are blind or have impaired vision or those with cognitive impairments may find them difficult, if not impossible, to use, disability advocates said.

“In this day and time I can’t imagine how . . . the Metro system [is] purchasing things and then . . . installing them and paying for them and they are not accessible to everyone,” said Denise Rush, who is blind and serves on Metro’s Accessibility Advisory Committee (AAC). “It is not acceptable. It is ludicrous.”

Dan Stessel, a Metro spokesman, said the transit system plans to have an audio prompt that will help people with hearing impairments installed on the new machines by sometime in the fall. It will be similar to ones used in automated teller machines. He did not provide a specific timeline for the prompts to be functioning.

Transit users with special needs said trips on the system — known for chronically broken escalators and elevators, bad lighting on some platforms, and poorly functioning loudspeakers that make it difficult to hear the next-stop announcements on trains and buses — can be intimidating.

“Traveling with partial sight is very difficult as it is,” said Barbara Milleville, president of National Capital Citizens With Low Vision. She said the lack of accessibility can be discouraging to those who depend on public transit.

“The transportation has to be accessible to people with disabilities,” she said. “It is very important to be able to travel on your own safely and not have to ask for help.”

Metro officials said that, also starting in the fall, the new SmarTrip dispensers will be equipped with Braille decals. But advocates for the visually impaired said many people with limited sight don’t know Braille and would benefit from an audible prompt.

“Why does this continue to happen?” Rush asked at a recent AAC subcommittee meeting where members said the audio component should have been a requirement in the purchase.

Although Metro said the dispensers will get the audio feature, Stessel also has called it “somewhat of a moot point.” He said the new machines will sell only standard SmarTrip cards, not the reduced-fare cards someone with a disability would typically use.

To qualify for a reduced-fare SmarTrip card, a customer has to be a senior citizen or have a valid Metro Disability ID. The reduced-fare cards are sold only at Metro sales offices, Stessel said.

Advocates say some people who are beginning to lose sight may not qualify for the discount and would want to use a machine with an audio feature. And they said some who qualify for the reduced-price cards may choose not to apply.

Under the Americans With Disabilities Act, Metro must provide equal access to public transit for those with disabilities. The transit system also encourages nearly 6,000 people with a disability to use its rail and bus services instead of the more costly door-to-door MetroAccess service.

“We sit here, we talk and we talk and we talk about why are all these people using paratransit and not using the fixed-rate system. And then we go and do something like this,” said Deborah Brown, president of the National Federation of the Blind, a regular Metro user and member of the AAC.

The new machines are part of Metro’s campaign to move riders from paper cards to the rechargeable SmarTrip cards, which Metro says are easier to administer and generally easier for riders to use. Transit users using paper fare cards are charged $1 extra per ride.

Metro has purchased 100 dispensers — priced at about $12,000 each — that are being installed at Metrorail stations, and the agency is in the process of acquiring another 100 machines, officials said. Vending machines have been installed at 47 stations. Riders can also purchase the SmarTrip cards at Metro sales offices and some retail stores.

Eventually, the plastic rechargeable cards will be available at all 86 Metrorail stations on every mezzanine.

Ramon Abramovich, a project manager with Metro, said the machines already have the hardware for the audible prompt. “It is a matter of designing the software and recording the appropriate phrases and loading that software,” Abramovich said.

He said the transit system is working with its vendor to incorporate the audio on the new machines.

The chairman of the accessibility commission, Patrick Sheehan, who is blind, said the group expects Metro to set a deadline for adding the audio function.

“It concerns me that we are having to retrofit the accessibility, which should be a standard part of anything that we are buying,” he said.