One of the biggest flaws in Metro’s “Rush Hour” promise program is that it’s harder for bus riders to receive a refund for delayed travel.

That challenge has reportedly manifested itself in the number of bus riders who have successfully claimed refunds.

NBC-4 and NBCWashington.com reported that only 50 MetroBus riders have received credits under the program, while Metro has reimbursed 26,000 rail passengers.

Under the Rush Hour promise program launched at the end of January, Metro riders can receive refunds on any rush hour trip that is delayed by 15 minutes or more. Under the system, rail passengers with registered SmarTrip cards will receive refunds automatically. MetroBus riders, meanwhile, have to request a refund online.

Metro spokesman Dan Stessel told NBC-4 that disparity can be attributed to the relative ease of getting a refund for rail passengers.

“The fact that rail is automated makes a big difference. Unfortunately, [there’s] no way to automate the process for bus because riders do not “tap out” at end of [a] trip,” Stessel told the news station.

The Rush Hour promise program launched last month as an accountability measure. While the 26,000 reimbursements for rail passengers seems high, Metro said 90% of all rush hour trips have arrived within 15 minutes of their scheduled time.