Three weeks into the metro area's latest traffic congestion relief scheme -- combination MnPass and carpool lanes on Interstate 35W -- south metro commuters appear satisfied yet still curious about the changes.

The Minnesota Department of Transportation reports that more than 3,000 people now have transponders to pay tolls on I-35W, and about 1,100 vehicles use them each day. The average toll has been less than $2, but when the weather took a wintry turn for the worse last week, the price of a quick trip peaked at $8.

Still, MnDOT's traffic monitor showed "it was a lot less congested than any of the other facilities out there," said Nick Thompson, the engineer in charge of the project.

Commuter Tom Minneman agrees: "Since they've turned on the lanes, I've noticed that there are fewer and fewer instances of these backups that 35 is known for."

But Minneman, like others who have studied the lanes in action for the past three weeks, has a few questions about the system's nuts and bolts. The restricted hours have changed, there's a bunch of new signs, and as single drivers whiz by in the MnPass lane, other drivers can't help but wonder: Are they playing by the rules?

"Before it was pretty easy to pick out the violators," Minneman said. "I'm curious how the police are going to enforce it."

Here are answers to some of the common questions:

How are the rules enforced?

New equipment in State Patrol cars gives officers an audible signal as cars zip by in the MnPass lane. If the signal notes that no toll has been paid and the officer sees just one person in the car, they can ask them to pull over.

Similar equipment and techniques have been used on Interstate 394.

"It's not simple enforcement, but they've really honed it over the last few years," Thompson said.

Officers also watch for drivers who jump in and out of the lanes outside of the designated areas, crossing over the double white line.

Even if drivers have correctly paid the toll or complied with carpool rules, or if it's a time when the lanes are unrestricted, crossing the double white line is a no-no.

"There's certain areas of the road where we don't really want a lot of people weaving in and out of the lanes," Thompson said. "We're trying to manage some of the access with double white lines."

Scofflaws face a minimum fine of $142.

When are the lanes restricted?

The MnPass and carpool lanes have different hourly restrictions in each direction.

Northbound lanes are toll and carpool only from 6 a.m. to 10 a.m. The southbound lanes are toll and carpool only from 2 p.m. to 7 p.m.

That's a change from previous rules, when the carpool-only lanes functioned between 6 a.m. and 9 a.m. and 3 p.m. and 6 p.m. in both directions.

The new hours -- actually a net reduction in restricted time -- keep I-35W in line with the hours on I-394 and also match up better with today's rush hour times, officials say.

"The old hours were set in the mid-1980s and hadn't been adjusted at all," Thompson said.

Drivers who still aren't sure if the lanes are open can look for three things to see what lane restrictions are in place.

First, check out the static signs that list the time of day the lanes are restricted. Second, if the MnPass lane is open, there will not be a diamond above it on the electronic signs. And third, the electronic price signs will say "Open" instead of listing a dollar amount.

What's next?

MnDOT will turn on more of the electronic displays over the regular lanes on I-35W to help drivers navigate trickier conditions. A red "X" above a lane will indicate restrictions ahead, such as an accident that has prompted a closure. The displays will show suggested speeds that drivers can follow during difficult driving conditions such as winter weather.

But Thompson noted that dramatic improvements in I-35W traffic flow won't be likely until other projects -- especially the work around Crosstown -- are finished. "The true value of these systems doesn't come into play until next year," Thompson said.

Katie Humphrey • 952-882-9056