New congestion-alleviating proposal from Springfield would add extra lanes, accessible via toll

Under one proposal for I-55, tolls in new lanes would increase at peak congestion times, giving drivers an incentive to stay off the road, and allowing the highway to operate at higher capacity and traffic to move faster.

The Chicago area has some of the longest commuting times in the nation, costing $1,445 a year per driver in lost time and gas. But some of the city’s busiest routes may only exceed their maximum capacity for a few minutes a day. The reason Chicagoans spend so much time and money on sitting in traffic isn’t just a lack of capacity; it’s also about how Illinois pays for roads.

That’s why a new proposal from the governor and a bipartisan group of lawmakers may succeed in cutting the cost of commuting where previous efforts have failed.

Through a public-private partnership, the state would add new lanes to the Stevenson Expressway (Interstate 55) on a 25-mile stretch between the Dan Ryan Expressway and the Veterans Memorial Tollway, and would pay for them through tolls. Drivers would be able to use the existing lanes for free or could opt to bypass the traffic by paying the tolls.

Drivers in Illinois may be wary of tolls, which in the past have stayed in place long after they had paid for the projects they were intended to fund. But unlike previous projects, at least one version of the proposal would use toll money not just to fund the new lanes but also to keep traffic moving freely.

The version favored by the governor, “dynamic pricing,” would allow tolls to vary depending on demand. Uber with its “surge pricing” and many other businesses such as airlines and hotels operate under the same principle. A few U.S. cities have recently adopted this approach to managing roads; if employed on a wide scale, toll roads with dynamic pricing could potentially end congestion altogether.

Congestion exists because traffic has to move more slowly to accommodate more cars. At first, drivers slow down so more people can enter the road, but when traffic reaches a certain point, the process grinds to a halt. Nobody can move or get off the road, so even though traffic is moving much more slowly, the road isn’t accommodating more people. Though drivers may assume a congested highway is overloaded, the road is actually operating at half its maximum capacity and could potentially carry twice as many vehicles at higher speeds.

In fact, major highways may only operate at full capacity for a few minutes a day before the excess traffic causes them to slow down. But because the jams caused in those few minutes reduce capacity, the road remains congested for hours afterward even though the number of cars on the road may be relatively few by then.

Unlike a fixed toll, congestion charging can keep roads running at full capacity by providing drivers incentives to avoid the road at peak traffic times. Prices are highest when demand is also highest, which encourages drivers to travel at different times or use public transportation. Using prices to control traffic volumes means the road isn’t just moving faster with less congestion; it’s also moving more cars. That means less land is needed for roads and less gas is burned sitting in traffic.

The proposal is not perfect. Because dynamic pricing would only apply to the new lanes, the remaining free lanes would still suffer from congestion long after peak demand has subsided. Tolls would have to remain at their highest level until the existing lanes start moving freely, which only happens when demand falls well below its peak. That could mean higher tolls are imposed for as much as twice as long as when all lanes are tolled.

This new proposal may help demonstrate to drivers leery of adding new tolls that dynamic pricing has benefits that exceed those of traditional fixed-toll projects. Dynamic pricing could then be expanded to other roads, using the additional revenue either to fund new capacity or to reduce existing gas and vehicle taxes.

Lawmakers still have to approve the project, and dynamic pricing is only one of the proposals before the General Assembly. Those considering the various road projects should know that a dynamically priced highway can double the amount of capacity added compared with building more ordinary lanes, and can manage demand more effectively than fixed tolls.