E-ZPass detectors and cameras are in place along parts of the 95 Express Lanes. (Robert Thomson/The Washington Post)

The 95 Express Lanes project in Northern Virginia is far enough along to allow testing of the tolling equipment to be used when the high-occupancy toll system opens in early 2015.

Drivers on the Capital Beltway saw a similar phase of testing during the final phase of construction on the 495 Express Lanes in 2012. This new testing is a bit different. The Beltway’s express lanes were a new system in the middle of the highway. The northern portion of the 95 Express Lanes project will convert today’s High Occupancy Vehicle lanes into HOT lanes, as well as add new lanes to the south.

So drivers in the I-95/395 HOV lanes will see marked vehicles traveling along in the lanes to perform tests on the equipment, including the gantries that house cameras and toll-reading equipment. Despite the presence of these test vehicles, the HOT lanes are still in the construction phase and won’t be collecting revenue for months.

Just as they did with the Beltway lanes, the test vehicles will help the project’s managers fine-tune the traffic-monitoring and tolling systems in the roadway and at the operations center in Alexandria.

The express lanes, with their special rules for carpooling and their all-electronic tolling, are the most complicated driving system we have in the D.C. region. If you are thinking about using them along this 29-mile long portion of I-95/395, it’s a good idea to start familiarizing yourself with the operation. Many things about the system will be familiar to drivers who have used the Beltway express lanes, but there also will be significant differences.

What’s similar. Because it’s all-electronic tolling, drivers need to have E-ZPass transponders, either the regular kind or the Flex version that has a switch allowing drivers with at least two passengers to claim the free exemption for carpooling. The tolls allow the state’s private partners in the construction and operation of the lanes to recoup their investment during their long-term lease. The tolls will be higher when more drivers want to use the lanes and drop when fewer drivers are interested. There’s no upper limit on the tolls, but the express lanes operators say they probably will range from a low of 20 cents per mile about 80 cents per mile. They anticipate that a typical trip will cost $6 to $8.

Not everyone would want to drive the full 29 miles, just as not everyone drives the full 14 miles on the Beltway express lanes. At the height of rush hour on the Beltway, a full-length trip from south to north on the express lanes can cost about $12.

What’s different. On the Beltway, almost all of the access points are at interchanges. Only at the northern and southern ends of the express lanes do drivers have a chance to move between the Beltway’s regular lanes and the express lanes. On the I-95/395 version, they will have several chances to move between the express lanes and the regular lanes. Also, a driver won’t lock in a toll for the full 29-mile trip. There will be a point where the driver will need to watch for message boards indicating the cost of staying in the express lanes for a second segment.

The lanes will be reversible, just as the HOV lanes are today. Hybrids, which today get a free pass if they have the proper clean-fuel license plates, will be subject to the same rules as other vehicles once the HOT lanes open. Driver will need E-ZPasses to either pay tolls or claim the carpool exemption if they have at least two passengers.