Washington area drivers are getting an early holiday gift: The 95 Express Lanes are set to open Dec. 14 along the project’s full 29 miles in Northern Virginia. And, for the first two weeks, drivers can use them for free.

That free-ride period should benefit both regular commuters and holiday getaway drivers because it will add capacity to Interstate 95 at no additional charge. The all-electronic tolling system is scheduled to take effect Dec. 29.

The 95 Express Lanes will link with the 2-year-old 495 Express Lanes on the Capital Beltway to form a toll-road network of about 40 miles stretching north to the offices and shopping in Tysons Corner. The commonwealth hopes to expand that network west from the Beltway along a congested stretch of Interstate 66.

It’s important for drivers to remember that during the transitional period after the lanes open, HOV3 rules remain in effect. During peak periods, drivers in the middle lanes of I-95/395 must have at least two other people aboard (HOV3) or risk getting a ticket. As is also the case now, the lanes are open to all drivers during off-peak periods.

Here’s your quick-study guide on how the 95 Express Lanes will work after opening this weekend.

What are HOT lanes?

The acronym stands for high-occupancy toll. Drivers who meet the carpool rules can travel for free. Others must pay a toll.

How do HOT lanes differ from HOV lanes?

HOV, or High Occupancy Vehicle, lanes have been around for decades in the D.C. region. They encourage carpooling by offering drivers a quicker trip than they would get in the regular travel lanes.

HOT lanes are a much newer idea. The first set, the 495 Express Lanes, opened on the west side of the Capital Beltway in Virginia in November 2012.

What are the 95 Express Lanes?

They are HOT lanes, the product of a partnership between the Virginia government and a private consortium that shouldered most of the construction costs in return for a 76-year lease to operate the lanes and collect the toll revenue. The same consortium, Transurban-Fluor, built and operates the 495 Express Lanes.

Where are the 95 Express Lanes?

The lanes follow a 29-mile route along I-95 and I-395 between Garrisonville Road in Stafford County and the Edsall Road area just north of the Beltway. At the Beltway, there’s a link to the 495 Express Lanes, which will create a HOT lanes network of about 40 miles between the southern suburbs and the Tysons Corner area.

The southernmost nine miles in the middle of I-95 are all new lanes. North of that point, the project expands the former HOV lanes by adding a third lane.

What’s not HOT?

From the express lanes’ terminus on I-395 around Edsall Road north to the D.C. line, the highway’s middle lanes continue under the old HOV3 rules. During peak periods, drivers must have at least two passengers with them. At off-peak hours, the HOV lanes are open to all drivers.

When will the lanes open?

The new lanes and ramps are scheduled to open Sunday evening.

Until Dec. 29, drivers will not be tolled. However, they will need to comply with the HOV3 rules along the entire route during peak periods.

What happens during the transition?

To prepare for the opening, all the new express lanes’ signs will be uncovered. The illuminated message signs will convey the HOV rules, rather than tolling information.

Operators will continue to test the tolling equipment in the gantries, but drivers will not be charged.

During the weekend of Dec. 26-28, expect nighttime lane closings while crews remove the HOV signs. Otherwise, lanes are open to all travelers through that long Christmas weekend. Drivers in the Monday morning rush on Dec. 29 will be the first to experience the tolling system.

When will tolling rules be in effect?

The tolling rules will be in effect 24 hours a day, seven days a week.

How are tolls collected?

There are no tollbooths. The gantries communicate with the vehicles’ E-ZPass transponders and record the tolls. The same system is used on the Beltway express lanes.

What if I carpool?

If you plan to have at least two other people in your vehicle, even occasionally, you want to get an E-ZPass Flex. It’s a type of transponder developed specifically for use in the Virginia HOT lanes. When carpooling, switch the setting to “HOV on.” Listen for a beep from the transponder to indicate a successful switch.

Using the E-ZPass Flex in the HOV setting is the only way for carpoolers to claim the free ride in the express lanes.

What if I have no E-ZPass?

You will want to get one. Drivers who use the lanes without a transponder still will be tolled. Cameras in the gantries will record images of the vehicles’ license plates, and the registered owners will be billed.

In addition to the toll, the driver will pay a fee that escalates as time passes.

How can I get an E-ZPass?

If you already have an E-ZPass issued by any agency, it’s good in the express lanes.

Virginia’s E-ZPass program no longer charges a monthly account maintenance fee.

To sign up for the Virginia E-ZPass program online, use this link: ezpassva.com.

The Virginia and Maryland programs are the only ones that offer the E-ZPass Flex. To see details on the Maryland program, go to ezpassmd.com.

District residents can sign up for E-ZPasses through the Virginia or Maryland programs.

In Virginia, travelers also can get transponders at E-ZPass Service Centers, AAA Mid-Atlantic stores, some Department of Motor Vehicles locations. and some Giant Food and Wegmans stores. On the Virginia Web site’s home page, click on the link that reads, “E-ZPass Locations” for details and a map.

Drivers also can call E-ZPass Virginia for more information: 877-762-7824.

I have a regular transponder. Can I swap for a Flex?

Yes. Drivers who already have Virginia E-ZPass accounts, the ones most likely to want a swap, can go to ezpassva.com and click on the “Switch to E-ZPass Flex” link.

What could go wrong?

With highway-speed electronic tolling, the gantries give drivers no feedback on whether the toll was recorded successfully. There’s no “Thank you” sign, no “Low account balance” or “Low battery” warning, no red light for a failed payment.

So these two things are especially important: Be sure to follow the instructions on how to mount the transponder to the windshield. Don’t press it to the glass. Don’t hold it out the window. Otherwise, there’s a good chance that the tolling equipment won’t detect the device.

In case the transponder transaction fails and a bill is generated based on your license plate number, make sure your tag matches the plate number listed on your E-ZPass account.

And make sure you pay the bill in a timely manner to keep fees and penalties from accumulating.

What will the toll be?

There’s no upper limit on the tolls, which will vary with the amount of traffic in the lanes as well as the distance traveled. The express lanes operators estimate the range at 20 cents to 80 cents per mile. So if you drove the entire route during a peak period, your toll might be about $23. Because the toll rates and the length of trips will vary, the operators expect the average toll would be more like $6 to $8.

What’s different from the Beltway HOT lanes?

Drivers in the regular lanes on I-95 will have more chances to enter and exit the express lanes than they do with the Beltway version. Drivers in the express lanes will encounter points where they must decide whether they want to continue in the lanes, based on a new set of toll rates displayed for next express zone.

At peak periods, northbound drivers also have decisions to make where the express lanes end near Edsall Road. If they are HOV3 carpoolers, they can remain in the lanes. If they are toll payers, they must exit into the regular lanes.

Southbound drivers will want to be sure that they have their E-ZPasses engaged when they pass from the HOV3 lanes into the 95 Express Lanes.

The reversible-lane schedule will be maintained throughout the entire express lanes/HOV3 lanes system.