On a recent Tuesday, Metro Transit police officers Noah Landers and Richelle Knode boarded a southbound Blue Line train looking for riders who hadn’t paid their fare. It didn’t take them long to find a couple headed to the airport with airline tickets in hand, but no train ticket.

The couple were asked to get off at the 46th Street Station and buy tickets before continuing their trip.

Booming light-rail ridership is being monitored by a growing transit police force — and curious fellow passengers. Between January and September, the Blue Line provided 7.16 million rides. Since its debut in June, nearly 3.5 million rides were taken on the Green Line, which saw weekday ridership in September alone average 37,170 — or 35 percent higher than projections for 2015.

Though trains are crowded, riders such as Michael Hall say they don’t see many people buying tickets from machines on platforms, and they wonder how many freeloaders are getting on board.

Metro Transit says more than 98 percent of riders pay the required $1.75 fare ($2.25 during rush hours). Of course, some don’t.

“On a system built on the honor system, people are going to try to take advantage of it sometimes,” said Metro Transit Deputy Police Chief A.J. Olson. “That is not a big number. Most people are paying their fare.”

Metro Transit has 12 full-time police officers inspecting fares on the Blue Line, and 12 more on the Green Line. When additional officers are hired, the number on the Green Line will rise to 20.

Officers ride the rails at all hours of the day; through September they had asked 958,719 riders to show proof of payment. They have issued 7,783 warnings, including to the couple caught heading to MSP. Officers have issued 1,180 citations, a misdemeanor carrying a $180 fine plus administrative fees.

In 2013, the agency provided more than 10 million light-rail rides, checked tickets of 1 million riders and issued 7,880 warnings and 1,450 citations. Olson said Metro Transit has a goal of checking 10 percent of light-rail riders.

Paying fare is most cost-effective

A majority of riders don’t visit a ticket machine because they are using electronic fare cards, which are to be tagged at card readers on each platform. Those who walk onto a train without tagging their card, giving the appearance that they did not pay, are not necessarily taking a free trip.

Fares on buses and trains are good for 2½ hours and allow riders to use both modes of travel. Riders transferring from a bus to a train don’t need to pay again. Though riders should be tagging their cards when transferring, Olson said sometimes they don’t for fear another fare will be deducted. Those riders can’t be cited.

Neither can holders of prepaid cards, such as Metropass or monthly Go-To Cards. Technically, they have paid their fare, too, but tagging helps the agency track ridership and lets companies that subsidize know they’re being used.

Officers might catch more fare evaders if that were their only duty, Olson said.

“Their primary duty is to create a comfortable riding environment for the public so they know the transit system is safe to ride,” Olson said.

So while the odds are high that you won’t be caught sneaking on a train, “it’s still cost effective to pay a fare than take the chance of getting caught,” he said.