All-electronic tolling along I-95 in Northern Virginia began on Dec. 29, 2014. (Robert Thomson/The Washington Post)

Tolling began one year ago Tuesday on 95 Express Lanes, yet their full impact on the D.C. region’s transportation system isn’t apparent yet.

So far, the high-occupancy toll (HOT) lanes are performing pretty much as billed. They provide a quicker and more reliable trip for toll payers and for carpoolers than do the regular lanes along 29 miles of Interstate 95 between the far southern suburbs of Stafford County and the spot just inside the Capital Beltway where they link with the I-395 High Occupancy Vehicle (HOV) lanes for the remaining eight miles to the D.C. line.

The vehicles most likely to be found in what are often derided as “Lexus Lanes” are Toyotas, Hondas and Fords. According to a study for Transurban, the company that operates the express lanes on I-95 as well as on the Capital Beltway, Lexus drivers account for 3 percent of the traffic.

[What we worried about when the express lanes opened]

A study done for Transurban in September by KRB Research found that 37 percent of the drivers in the 95 Express Lanes make $100,000 or more. Among the rest, 43 percent earn $50,000 to $100,000. (The $100,000 plus crowd is a bit more active on the 495 Express Lanes, where they represented 41 percent of drivers. The study said that nearly half of the HOT lanes drivers use both the Beltway and I-95 systems. The better-off drivers have the best representation in that group. According to the study, drivers who earn more than $100,000 account for 44 percent of the traffic using both sets of lanes.

The study also found that 34 percent of the weekday trips in the 95 Express Lanes are taken by drivers who qualify as HOV (mostly carpoolers). These are the drivers who get a free ride because they use the E-ZPass Flex with the switch flipped to the HOV setting.

Transurban officials cited traffic data from the Regional Integrated Transportation Information System to show the 95 Express Lanes providing a time savings for both the HOT lanes drivers and the regular traffic on I-95 in September compared with travel times a year earlier. While HOT lanes travel saves more time and is more consistent than travel in the regular lanes, Transurban said the data in the chart below shows drivers in the regular lanes of I-95 were better off than in the previous year.

The chart compares travel times for northbound traffic in the regular — or general purpose — lanes on I-95 between September 2015 and a year earlier. (Transurban image)

Note that the chart shows travel times for the entire route where drivers can choose between the express lanes and the regular lanes. Some parts of the trip may be slower than others, and some days are clearly better than others.

And like so many other aspects of the HOT lanes system, the travel times are likely to evolve, as travel habits change and the infrastructure changes.

We’re years away from knowing whether housing patterns will change, because the 95 Express Lanes made it more convenient for commuters to live in the outer suburbs while working in Alexandria, the District, Arlington and parts of Fairfax County that include Tysons Corner. But changes in the express lanes network are likely to have a big impact, as well.

One of the biggest problems for I-95 drivers today is the southbound merge near Garrisonville Road where the express lanes and the regular lanes come together. At that spot, the HOT lanes are not working as planned. In the fall, Virginia transportation officials laid out a project to extend the HOT lanes two miles farther south to reduce some of that congestion, which affects drivers in all the lanes.

Meanwhile, the officials also unveiled a plan to extend the 95 Express Lanes north along I-395 to the D.C. line, replacing today’s HOV lanes with HOT lanes.

But the biggest plan of all is the one that would create HOT lanes on Interstate 66, both inside and outside the Beltway. When the system is completed around 2021, a driver willing to pay the toll could use the HOT lanes to get from a home near Woodbridge to a job along the I-66 corridor.

But if the state’s HOT lanes plans work as billed, the entire HOT lanes network will wind up with a much more robust system of carpooling and commuter buses than what we see today. Northern Virginia is far more likely to see its commuter bus network develop than it is to see any extension of Metrorail during the next decade or more.

Also, the creation of the express lanes network is key factor leading Northern Virginia to pursue discussions with Maryland about improving the Potomac River crossing at the American Legion Bridge and the Montgomery County side of the Beltway.

So the first anniversary of the 95 Express Lanes isn’t so much a time to assess toll rates or traffic volumes in what’s still just the start-up phase for this route. The anniversary is more of a reminder that Virginia has set the stage for a major transformation of the travel system in the D.C. suburbs.