The Beltway's Brain

To get a taste of Virginia's transportation future, take a spin on the 495 Express Lanes project where sensors, artificial intelligence and dynamic pricing combine to optimize scarce capacity on the Capital Beltway.

by James A. Bacon

If highways had IQs, the newly reconstructed Capital Beltway in Northern Virginia would be the Einstein of asphalt. The 495 Express Lanes have 75 electronic signs and message boards, 36 gantries and tolling points, 80 microwave-radar sensors to measure traffic speeds and innumerable video cameras to monitor road conditions, all tied together by 45 miles of high-bandwidth cable.

The beltway's brain, where data compiled by the sensors is assimilated and acted upon, is located in a non-descript building in an industrial park just off I-95 in Alexandria. There, employees of Capital Beltway Express (CBE) keep a close eye on traffic, dispatching incident-management crews in the event of accidents or flat tires, providing customer service and otherwise ensuring that the $2 billion toll road runs smoothly. But the most important decisions -- the price of tolls -- are not made by humans.

Every 15 minutes a computer algorithm adjusts the rates for nine highway segments, depending upon the level of demand for each. An employee watches the algorithm, but from what I could observe when visiting the control center for more than an hour last month, the task of watching sine waves undulating across a computer monitor did not appear to be a terribly exciting one.

Humans will re-enter the pricing picture, but only briefly, when programmers periodically incorporate traffic data based upon the expressway's real-world experience to update the algorithm. Says Jennifer Aument, vice president of corporate relations for Transurban, which owns 90% of CBE: "The system will get smarter and smarter."

I had come to visit the 495 Express Lanes control center to get a peek at the future of transportation in Virginia, particularly in Northern Virginia which by some measures has the worst traffic congestion anywhere in the country. New highway capacity is hideously expensive to build in the Old Dominion, and even moreso in the Washington suburbs where the high cost of real estate makes the acquisition of right of way prohibitive. Given intense opposition to tax increases, Northern Virginia cannot build its way out of traffic congestion. That leaves only one alternative. As Aument says, "We have to get smarter managing what we already have."

The 495 Express Lane project, which runs 14 miles between Interstate 95 and the George Washington Parkway, uses technology and tolls to guarantee access to free-flowing express lanes for those who, at any given moment, place the greatest value on their time. The technology makes it possible to vary the price directly in response to changes in traffic volume. When volume increases, so does the price; when traffic decreases, the price goes down.

The $2 billion express lanes project creates economic value in four ways. First, it adds four new lanes to the Beltway, expanding capacity. Second, it provides three new Beltway access points in and around the Tysons business district. By allowing some toll users to exit closer to their destinations, it takes cars off congested local roads. Third, the express lanes provide time savings for people who wish to bypass congestion. Fourth, it provides predictability for everyone, whether they use an express lane or not. Northern Virginia drivers typically tack on 15- to 20-minute buffer times around meetings to give themselves leeway in the event of gridlock. Just knowing they have the congestion-free option, should traffic slow, allows people to reduce the dead time, even if they don't actually end up using the lanes.

Capital Beltway Express is a collaboration between Transurban, an Australian toll-road company, and Fluor, a global construction company, in a public-private partnership with Virginia. The same partners are constructing the Interstate 95 express lanes, which, when complete in 2014, will merge seamlessly with the 495 lanes and will be run out of the same operations center. The state contributed $409 million to the Beltway project, mainly to offset the cost of rebuilding some 58 bridges and overpasses to accommodate the four extra lanes. Dating back to the 1960s and earlier, those facilities had accumulated a significant maintenance backlog. Transurban and Fluor invested $350 million in equity, and the rest came from bonds to be repaid with toll revenues.

As part of the deal, buses, motorcycles and vehicles with three or more drivers use the express lanes for free, treating them, in effect, like High Occupancy Vehicle (HOV) lanes. Thus, the bonds are being repaid by drivers who use the lanes to avoid congestion, not ride sharers or the general public.

Most toll facilities, like the Dulles Toll Road, publish their rates in advance and stick with them for months or years at a time. Some, like the Midtown Tunnel-Downtown Tunnel project in Norfolk, varies pricing by time of day but does so in accordance with a posted schedule. The 495 Express Lanes project is one of only five in the country that uses dynamic pricing, in which the price varies depending upon traffic conditions throughout the day.

Integrating dynamic pricing for single-occupancy vehicles with HOV lanes was major challenge. The first trick was figuring out how to allow buses and carpools onto the expressways while weeding out cheaters, who comprise roughly one quarter of HOV traffic on nearby I-95. The solution: Sell flex transponders that allow drivers to switch back and forth between single-driver and shared-driver mode. To make sure drivers don't abuse their flex transponders, gantries take front and back photographs of vehicle licenses. The system then alerts state troopers, whose time is paid for by the tolls, to visually confirm that there are at least three riders in vehicles claiming HOV status.

The next trick was conveying the pricing information. With nine segments varying independently and 11 exits and entrances, the rates are complex. It isn't easy to put pricing information on a sign that drivers can read without getting distracted while driving at 55 miles per hour. CBE settled upon a sign that contained three pricing slots detailing maximum prices for the most common exit points.

Sensors capture data on the volume and speed of car and the algorithm sets toll rates that guarantee speeds of at least 45 miles per hour. Traffic follows patterns that make volumes predictable to some degree: Each day of the week experiences surges during morning rush hour and evening rush hour. But outside factors often intrude. There can be spillover effects from Interstate 66 or I-95. Traffic accidents and even flat tires on the Beltway or connecting roads can cause bottlenecks and divert traffic to alternative routes. Holidays, summer vacation and even special events can make a difference. The algorithm updates the tolls every 15 minutes, adjusting rates in increments to avoid sharp increases.

A month after the express lanes opened, traffic volumes still were relatively light. Drivers were still adjusting to the new traffic patterns and getting accustomed to the idea of paying tolls to skirt past congestion. Charges varied between the minimum of $0.25 per trip to a peak of $4.00, but Aument says that peak rates most likely will increase as more drivers avail themselves of the express-lane option. Higher volumes, she adds, will mean greater fluctuations in the number of users and wider swings in prices.

While it is still too early for an authoritative analysis of who is using the express lanes, there is enough anecdotal information to dispel the characterization of them as luxury "Lexus lanes" reserved for the automotive 1%. For starters, motorcycles, buses and cars with three or more riders are using the lanes for free, says Aument. Indeed, Fairfax County will be expanding its municipal bus service this month.

The experience from other express lanes suggests that most toll payers use the lanes only a couple of times a week, typically when they are in a time pinch. Child care is a big factor. Parents use the express lanes to pick up their children from day care on time, sometimes avoiding late fees that run as high as $1 per minute. Businesses also use the lanes to boost productivity. Truck drivers can squeeze in more stops and make extra deliveries. Business people can schedule more sales calls. "It's not just the time savings," says Aument, "it's the predictability."

CBE has released no official traffic counts yet but Aument says volumes appear to be in line with expectations. "We know it will take some time before we're running at full speed" -- the marketing/communications plan is scheduled to run through the duration of 2013. All things considered, she says, "We're very pleased. We're seeing traffic grow almost every day."


This article was made possible by a sponsorship of the Piedmont Environmental Council.



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