While millions of subway riders were socked with a fare increase last year, a cadre of MTA workers raked in more than $100,000 in overtime, thanks to costly union work rules, The Post has learned.

In all, 20 employees took home six-figure overtime payouts in 2011 on top of their regular salaries, according to payroll information that The Post obtained under the Freedom of Information Act.

The biggest hog was LIRR train-car repairman Vincent Blackburn, who earned a staggering $135,684.53 in overtime last year — more than doubling his base salary of $66,539.12.

Blackburn — along with seven of the top 10 highest overtime earners — is employed at the Long Island Rail Road’s Richmond Hill, Queens, repair facility, an OT gold mine affectionately known by staffers as “Rich Man’s Hill.”

Workers there benefit from an old labor agreement known as “Rule 24,” which requires the railroad to fill all vacant slots on certain work shifts — even if the manpower isn’t needed.

Thanks to that, workers at the facility — the only one governed by the arcane rule — can earn an obscene amount of overtime that is doled out based on seniority.

A large number of vacancies at the shop also contributed to the overtime rates, officials said.

Blackburn earned a total of $202,323.65 in 2011, including other work bonuses, making him the 44th highest paid employee among the agency’s 66,000 workers.

When reached by phone yesterday, he told The Post: “I’m going to say this one time and one time only. I got nothing to say to you!”

That obscene salary is higher than some of the agency’s top officials, including MTA Chief Operating Officer Robert Foran, who earned $197,532.25.

Christopher Garrick, who also works at the Richmond Hill facility as a car repairman, was the second highest OT earner.

He got $124,308.08 in overtime last year, padding his base salary of $64,367.42 to reach total compensation of $189,140.03.

The MTA has tried in recent years to curb excessive overtime, which can also contribute to pension padding.

Workers nearing retirement tend to work more hours to add to their pensions, which are based on the last few years of their salary history.

“In 2010, overtime hours were reduced by 12.6 percent, saving $13.4 million, and remained at that reduced level in 2011,” said MTA spokesman Aaron Donovan.

OT is down by 6 percent for the first four months of this year, he said, but “some overtime is ultimately the product of work rules which can only be changed through collective bargaining.”

Riders were hit with a fare hike in 2011 and face planned hikes in 2013 and 2015.

State Comptroller Thomas DiNapoli – whose office has conducted several audits on MTA overtime – said more needs to be done to rein in overtime at the agency.

“We continue to find abuse and inefficiencies and a culture that accepts them,” he said. “More needs to be done to monitor overtime use to ensure it is justified and reduce it where possible.”

Additional reporting by Ikimulisa Livingston