Metrorail’s peak-of-the-peak surcharge has so far failed to move riders out of the most crowded part of rush hour, the transit authority staff says in a report to the Metro board.

Rush hour rail riders have been less responsive to last year’s fare surcharge than anticipated, according to the report on ridership and revenue, which will be presented to board members Thursday.

Rail riders now pay 20 cents extra for weekday trips that start between 7:30 and 9 a.m. and between 4:30 and 6 p.m., but only 3 percent in the morning and 3 percent in the afternoon moved their trips outside of those ranges.

Some advocates for the new charge, called the peak of the peak fare, saw it as a form of congestion pricing. The policy would ease the worst effects of rush hour crowding by creating a financial penalty for riding when the trains are most jammed.

A rider making trips on the shoulder of the peak — boarding, say, at 8:50 a.m. — might decide to save the 20 cents and board at 9:05 a.m.It’s not an unreasonable theory. Watch riders outside the fare gates, staring at the digital clock over the station manager’s kiosk, waiting for the time to change from peak to off-peak.

But much of the crowd at those hours consists of 9 to 5 workers, who have little flexibility about when to go in and when to head home. For them, “congestion pricing” was just another name for a fare increase. Also, many of those rush-hour riders are federal employees whose trips are subsidized through employer transit benefits.

The sluggish response to the congestion pricing idea is not exactly sad news for the transit authority, which still gets to keep the revenue.

The average length of a rail trip remained unchanged despite last summer’s increase in the distance-based fares. Ridership for the night-owl trains on Friday and Saturday nights increased, even though the riders now must pay full fares for what was an off-peak service.

Other financial penalties did have an effect: Ridership on the airport buses dropped 15 percent overall after riders on the 5A bus to Dulles Airport and the B30 to Baltimore Washington International Marshall Airport saw their fares nearly double.

The decline was sharpest on the B30, perhaps because many former riders on the Greenbelt to BWI run now prefer to take a MARC train from Union Station to the airport.

Newly created fare incentives to use SmarTrip cards rather than cash on a bus or a paper fare card on Metrorail also had an effect on riders, the report said.

On Metrobus, riders get a free transfer now only when they use the plastic SmarTrip card. The rate of SmarTrip use rose from 64 percent to 76 percent. On Metrorail, riders now pay 25 cents extra if they use a paper fare card. The rate of SmarTrip use rose from 76 percent to 79 percent.

All of these rates represent a comparison of September 2009-January 2010 with September 2010-January 2011. See a pdf of the report.

In focus groups, riders told Metro they find the distance-based fares too complicated, and the fare charts posted in the stations too confusing.One way to simplify the chart would be to impose a flat fare for all trips, rather than charge more for longer trips. That’s something the Metro board has not considered seriously, because it creates a jurisdictional conflict: Many suburban riders would pay less, while many riders in the region’s core would pay more.