Tolling techniques

Variable tolling takes several forms. Each is a response to congestion, and to the fact that limited space and limited revenue reduce the likelihood that new lanes will be built without toll financing. The new forms of tolling are used not only to pay for construction and to reward investors, but also to manage traffic through a technique known as congestion pricing.

Congestion pricing in the United States comes in one or two forms, the GAO report said. High-occupancy toll (HOT) lanes vary the toll according to current demand. The varying toll moderates the number of drivers entering the lanes so speeds can stay at 45 to 55 mph. The 495 Express Lanes on the Beltway and the other HOT lanes planned for Interstate 95 will be examples of that. HOT lanes offer a free ride to those meeting the HOV requirements, but charge other drivers.

The other format bases the toll on time of day, charging a pre-set premium price for travel during peak periods. The Intercounty Connector and Dulles Greenway follow that model. The traffic management goal is similar: The changing toll encourages drivers to use the highway when it’s likely to be less congested.

History and future

The first congestion pricing project in the United States was launched in 1995 in Orange County, Calif. The GAO report now counts 41 pricing projects either open or under development on highways, bridges, and tunnels. Tolls range from 25 cents to $14.

It looks like the way of the future. Some regions are planning networks of HOT lanes, the report says. (Virginia would be one of them, but Dallas-Fort Worth, Atlanta, Minneapolis-St. Paul, Seattle, and the San Francisco Bay area also are among those planning for such networks. The Metropolitan Transportation Commission of the San Francisco Bay Area proposes having a 570-mile network of HOT lanes by 2025.)

Performance

So how are they doing? The report describes the results of its research and other studies that examined how variable tolls have performed in relation to five goals. But the researchers note that not all projects were evaluated and that there are limits on the assessments.

1) Did travel time and speed improve? They improved on at least some sections of the five HOT lane projects evaluated. Sometimes, the GAO said, the improved travel times in the HOT lanes also led to improved travel times in the adjacent general purpose lanes. For example, a study found that peak-hour speeds on the untolled lanes along SR 167 in Seattle had increased by as much as 19 percent in 2010 compared with travel speeds in 2007.