For Northern Virginia commuters returning to work on Monday, a reminder: You will pay to use the new 95 Express Lanes.

Don’t use the lanes without an E-ZPass.

The 30 miles of reversible lanes between Garrisonville Road in Stafford County and Edsall Road in Alexandria will no longer be free to use come the Monday morning rush hour. The new lanes and ramps have been open since Dec. 14, but under existing HOV rush-hour rules.

That means single-occupancy vehicles will be allowed to use the lanes at any time to come north in the morning and to go south in the afternoon and evening, as long as those drivers have an E-ZPass activated and installed. The lanes use dynamic pricing to keep traffic moving at a steady clip. The more congested the regular lanes of I-95, the more expensive the Express Lanes.

All four-wheeled vehicles, including hybrids, must have an E-ZPass to use the lanes, 24 hours a day. For carpoolers — those with three or more people in the car — an E-ZPass Flex is required and should be switched into HOV mode.

Driving without an E-ZPass will land you a bill in the mail. Driving in HOV mode with fewer than three people in the car could land you a ticket, if you get caught. State police will be patrolling for cheaters.

The $925 million Express Lanes were constructed in just over two years by Fluor Corp. and The Lane Construction Corp. The project includes nine new miles of HOV lanes between Dumfries and Garrisonville Road, a third lane on 14 miles of existing HOV from the Prince William Parkway to Edsall Road, eight new or improved access points, nine new bridges and dozens of new signs and gantries.

AAA Mid-Atlantic on Friday declared the Express Lanes one of the top “milestones” of 2014 (behind the free falling gas prices).

“They will change the way we — motorists, carpoolers, and the owners of hybrid vehicles — commute on one of the busiest highways on the Eastern Seaboard,” the motorist rep wrote in a release. “Gone are the traditional HOV lanes. Hail the E-ZPass.”