BREMERTON — Reservations won't guarantee riders a spot on the most popular fast ferry runs between Seattle and Bremerton in January after a glitch in the reservation system led to overbooked sailings.

Kitsap Transit said on Tuesday that its two most popular fast ferry sailings— the 6:45 a.m. to Seattle and the 5:10 p.m. to Bremerton — had been overbooked for January. The agency estimates an average of 150 to 165 reservations were made for those sailings. The Rich Passage 1 can carry 118 passengers.

Kitsap Transit usually caps reservations at 88. In January, reservation-holders will be served on a first-come, first-served basis until the ferry is full, meaning riders will have to show up earlier for a shot at a seat or find a different way to work. It will also be tougher for walk-ons to get a seat on those sailings.

“We're just sorry that this causes a lot of uncertainty for reservation holders, the whole reason they're using the system is to have a greater certainty of getting a seat,” Kitsap Transit spokesman Sanjay Bhatt said.

Commuters first noticed something was awry while trying to book seats for January on Dec. 1, when the reservation window opened. Several people noticed what appeared to be an error in the system — each sailing showed up twice, with a different number of available seats.

“At that point when you see something like that you know there’s an issue,” said Greg Heilman, a Port Orchard resident who frequents the 6:45 a.m. boat to Seattle.

Since the most popular sailings in the morning and afternoon often sell out quickly, riders were surprised that seats were still available half an hour or more after the window opened.

Heilman, a project manager in Walt Disney’s Seattle office, picked the reservation with the fewest available seats, thinking one option must be invalid.

While he received a confirmation for each booking as usual, Heilman said many riders were left unsure if their reservations would be honored come January.

Kitsap Transit said the glitch stemmed from a software update pushed out by the reservation system’s vendor, RocketRez.

When the reservation window opened, riders had the option to book seats on New Year’s Day, when the ferry doesn’t run, according to Bhatt. The error was noticed quickly and the reservation period deleted, along with reservations made by riders during that time.

“The process happened within a matter of a minute or two, where the vendor deleted the reservation window and opened a new reservation window,” Bhatt said.

The result was two different “lists” of reservation holders — those who had booked spots right as the window opened and subsequently had reservations deleted, and an “active” list. Some commuters, realizing something was wrong, went back in and made a second set of reservations.

To help assuage the problem, Kitsap Transit is asking riders to cancel reservations they don’t need and offering free passenger tickets for the WSF car ferry to the first 30 passengers each day who volunteer to give up their seat on the 5:10 p.m. sailing from Seattle. Those tickets will cover the return fare from Seattle.

Everyone else will have to show up earlier than usual, and there’s no guarantee that a spot will be available, even with a reservation.

Commuters have also complained about transparency, arguing Kitsap Transit should have said something earlier.

Scott Usher, a Bremerton resident, rides the fast ferry daily to get to his job as a CPA in Seattle. Usher said he contacted Kitsap Transit soon after he made his reservations and was told the problem had been fixed and the duplicate reservations deleted.

Until Tuesday’s announcement, Usher said he heard nothing else about the status of his reservations from Kitsap Transit.

“My confidence is shaken because this is the second time there's been a vendor issue,” Usher said. “I think they've got to put time and effort into getting the right IT people working on the system so it's more transparent.”

Kitsap Transit said the delay was because of misinformation received from the vendor.

Initially, RocketRez told Kitsap Transit that fewer than 100 reservations had been deleted during the short time frame of the first reservation window. Believing the problem was a minor one, the agency announced it would honor all reservations, Bhatt said.

Mid-month, several frequent commuters requested the raw reservation data from Kitsap Transit, which showed that many sailings were booked far beyond the RP1’s 118-passenger capacity. The records request was the impetus for Kitsap Transit to question RocketRez about what they’d been told, Bhatt said.

Kitsap Transit staff went over the separate lists and tried to reconcile the number of extra reservations by hand. It wasn’t until last week that Kitsap Transit felt confident enough to put together a plan for dealing with the overbookings, Bhatt said.

"We are also up against the fact of a high no-show rate, it makes it a little challenging to say we're going to be overbooked on our sailings because we don't know how many of those folks are going to show," Bhatt said.

To fix the problem, Kitsap Transit is encouraging riders to show up early, consider taking the state ferry, and canceling reservations they know they won’t need. The agency will know more after the first week of January which sailings will have problems.

Bhatt said Kitsap Transit has talked to RocketRez and put up safeguards to stop a reservation window from being deleted again.

"Basically we had some conversations with our vendor about making sure they understand what we need, that we need to be able to lock holidays before the general public can start making reservations," he said.