Bay State rail commuters, fearful of another winter transit collapse, have been left standing during rush-hour because Keolis, the MBTA’s contractor, has failed to provide the required number of seats under its agreement with the T, a Herald review found.

Keolis is required to run a minimum number of trains and passenger cars each day, according to its contract with the MBTA. But commuters have complained they’re left standing in crowded aisles on long train rides to and from the city. They also note that the congestion makes it nearly impossible for conductors to collect fares for the cash-starved transit system.

The company fell short by more than 168,700 seats of the required capacity on nearly 2,500 commuter trains during the 16-month period from July 2014 to October 2015 — the most recent available data — according to the MBTA.

All of those trains operated during rush hour, the review found.

The commuter rail saw a surge in its seat shortage in October, to 8,784 missing seats on 179 trains — a more than 23 percent spike over the 7,121 missing seats on 145 trains in September, records show.

The review also found commuter train seat shortages weren’t just a problem during the winter months.

Some 334 trains ran short of the required number of seats in July and another 246 trains didn’t have enough seats in August, according to the T. By comparison, 190 trains ran without enough seats in February.

The MBTA currently fines Keolis just $527 per train for lacking the required number of seats — no matter how many missing ones there are. Commuters pay between $75 and $362 for monthly passes, depending on where they live.

MBTA spokesman Joe Pesaturo countered that commuter rail riders in October were offered the “second-most seats in MBTA commuter rail history” and emphasized that Keolis is providing an average of 98.68 percent of the seats required by contract.

But Ken Roberts, who has taken the train from Southboro to Boston almost every day for the past year, said he’s not impressed.

“A lot of action with no visible results means nothing to most commuters,” said Roberts, adding that he sees between 15 to 30 people standing per car every day on his commute.

“Many of the people are paying upwards of $250 a month with the expectation that they will have a seat, but they end up standing for about an hour. You already pay a lot, the trains are delayed and they don’t run on time. Not having a seat adds insult to injury,” Roberts said.

“The frustrating part is the conductors can’t make it down the aisle because of the crowding,” said Roberts. “When things start clearing out, then they will start collecting tickets and all those people get a free ride. They can’t even deliver the service you’re paying for or collect fares and they want to raise rates.”

Stephen Evanchik said he likes riding the train, but his commute from Beverly to Boston is often packed and standing room only.

“There’s like 200 people trying to get on a much shorter train in Beverly and then the train stops in Salem,” said Evanchik. “It’s like a clown car at that point. They’re standing in the aisles. The demand is there. It’s frustrating to say the least.”

Evanchik, who drove to Kendall Square for work for 10 years before he switched to a rail commute in September, said he’s worried a looming plan to revise the train schedules will only make seats more scarce.

“The new schedule for the trains is ridiculous,” he said. “They are removing trains in the middle of the commute, which will make things miserable.”

Keolis spokeswoman Leslie Aun insisted things are getting better and argued that the summer seat shortage wasn’t worse than February because those figures don’t take into account the roughly 4,400 trains that didn’t run at all that snowy month.

“With the exception of a couple months where we were adversely impacted by the winter storms, our numbers have been strong and trending in a positive direction,” said Aun in a statement.

“July 2015 was a challenging month in part because many of the federal inspections that had been postponed during the winter storms (when so much equipment was sidelined) came due all at once.”