With congestion pricing, toll rates in express lanes rise at times when more drivers want to use the highway, then tolls fall when demand is low. The simple logic of supply and demand can help to manage highway resources more effectively: Drivers will choose to enter or leave the express toll lanes based on the variable cost.
The toll rate can be finely calibrated to manage demand at a level that leads to faster, more-reliable travel times. Higher prices during peak periods may also reduce congestion by encouraging travelers to carpool, take transit, or consider alternative routes and times for their trips.
In this illustration: 1) Signs indicate upcoming points of access to the express toll lanes. 2) At the access points, signs indicate the toll charged to travel certain distances. Prices are set to ensure smooth traffic flow and reliable speeds in the express lanes. Transit vehicles and registered carpools typically ride free or at a discount. And 3) After a driver enters the express toll lanes, an overhead device reads the vehicle's electronic transponder and automatically charges the toll — similar to the Illinois Tollway's open road tolling system.