WASHINGTON — Metro is refunding 598 rush-hour riders for their significantly delayed trips Friday, the first day of Metro’s new automatic rush-hour refund program.

To qualify for the refunds, a rider’s trip must be during rush hour, must take at least 15 minutes longer than the longest possible scheduled trip at that time of day and must be taken using a SmarTrip card personally registered with Metro.

From previous data, Metro estimated about half of delayed rush-hour riders would not qualify since their cards were not registered with the agency online.

When including all times of day, Metro said 92.6 percent of the approximately 600,000 rail rider trips were on time Friday.

Metro calculates the “on-time measure” by adding the time to walk from the fare gates to the platform to the full scheduled gap between trains at that time of day, time to walk to another platform and wait the full scheduled gap between trains if there is any transfer involved, the actual length of the trip and the time to walk out of the station.

Metro did not yet have data available Monday morning on any bus refunds for Friday.

While the rail refunds are automatic for those who qualify, bus riders must fill out an online form requesting a refund.

Bus riders who fill out the form qualify if their delay of 15 minutes or more is due to something within Metro’s control like a bus breakdown, but not if the delay is due to something like a traffic jam.