On an average morning's commute on I-35W, it's not unusual for cars to be backed up in both general-purpose lanes, because of congestion, an accident or poor road conditions.

Meanwhile, traffic in the MnPass lane — the far left lane, marked with a diamond and reserved for buses, carpoolers and those paying a toll to use it — is typically moving swiftly.

The difference is enough to make even law-abiding drivers consider sneaking over for a bit. And if you've ever wondered what would happen if you did, you're not alone.

"We certainly do get a lot of questions about law enforcement out there," said Brian Kary, freeway operations engineer for the Minnesota Department of Transportation.

Since the MnPass lane on I-35W began operating in 2009, MnDOT has contracted with the State Patrol to have two troopers dedicated to ­policing it during rush-hour periods, said patrol spokesman Eric Roeske.

One trooper is stationed in the south and another on the north end of the MnPass stretch, which begins in downtown ­Minneapolis and ends just south of County Road 42 in Burnsville, Kary said.

The troopers "won't ignore other violations … but we're primarily there to enforce the MnPass lane," Roeske said.

Using a mobile reader in their squad cars, troopers can identify vehicles in the lane that don't have a MnPass transponder. Then they look for whether the drivers have another passenger with them. If they don't, they may be pulled over, Kary said.

In 2013, MnDOT data showed an average of 181 violators in the lane each day from 6 to 9 a.m.

Meanwhile, the troopers issued 5,409 citations last year on the stretch of 35W with a MnPass lane, and about 60 percent of those were for using the lane without a passenger or a transponder, MnDOT data show. That averages out to about 12 MnPass violations a day.

Depending on the county in which they are issued, tickets cost motorists between $140 and $150 each, Kary said.

Such enforcement is essential because it "helps maintain the integrity of the lane," he said. Without it, there would be too many violators and the lane would become just as congested as the other two.

Worth the risk?

The MnPass lane carries as many people — carpoolers, bus riders and those paying tolls via their transponder — as the two general purpose lanes combined during rush hour each day, Kary said.

From 6 a.m. to 9 a.m. during 2013, an average of 1,872 cars used the lane for carpooling, carrying 3,932 people. In addition, 1,223 single occupants drove with a MnPass transponder and 60 buses carried 1,696 passengers each morning, according to MnDOT data.

Kary said that on average, a driver can shave five to 10 minutes off their ­commute by using the lane in the morning, depending on how busy it is and how long they're on I-35W.

About 10,500 people currently pay to have a MnPass transponder to travel on I-35W, the vast majority of them Lakeville residents, he said.

Dana Nelson, who works in Bloomington and lives in Richfield, usually uses the MnPass lane only when she's carpooling, and "has no idea what that whole MnPass setup is," she said.

Just last week, however, she sneaked into the far left lane to pass a "really slow driver," she said, though she was by herself.

Other commuters said they wouldn't think of crossing the double white line, even to save time.

Tom Robin of Prior Lake, who carpools with his dad to Bloomington every day, said he would never consider using the lane if he weren't carpooling because it's not worth getting a ticket. "I see people get pulled over all the time," he said.