In the Seattle metropolitan area, a network wide variable tolling system would cost roughly $749 million to implement and $288 million to operate each year.
Made Public Date


United States

Summary Information

In the Seattle metropolitan area, a congestion pricing project was conducted to examine the driving behavior of 275 volunteer households who had vehicles equipped with GPS tolling meters similar to those used in taxis. The overall goals of the project were to examine how road users responded to price, determine whether variable tolling was a useful approach to road finance and management, and demonstrate how proven technology can be used to implement tolling on large transportation networks without having to deploy substantial physical hardware at the roadside.

Between July 2005 and March 2006 the project observed participant driving patterns before and after hypothetical tolls were imposed on all major freeways and arterials in the Puget Sound region. The technology installed in each participant's vehicle recorded the vehicle's location and matched the vehicle's position to a map of toll roads within the tolling meter. During the before period, drivers were able to view an in-vehicle display that showed the name of the road they were traveling on. During the after period the display showed the name of the road as well as the toll rate per mile and the cumulative toll for the current trip. Periodically, the on-board unit would communicate to a central computer using a cell phone network and reconcile toll charges to each participants account.

To encourage participation, drivers were given an expense account from which to deduct toll charges. If any money remained in the account at the end of the study, the participants were allowed to keep it. The intention was to provide incentive to modify driver behavior and budget toll road use. A website was set up to allow participants to monitor their travel, reflect on trip choices, and gauge the overall consequences of those choices on their account balances.

To estimate the cost to implement a similar system in the Puget Sound region, researchers developed a high-level cost model based in part on findings from a Dutch Cost Monitor model applied to the central Puget Sound area. The model assumed that 90 percent of the vehicles located within the tolling network would opt for the "Main Program" and have tolling equipment installed within the vehicle. Other users would opt for the "Occasional User Program." The model also assumed that 10 percent of the vehicles in select counties adjoining the tolling area would also have OBUs installed.

The table below excerpted from Table-1 of the source report summarizes the results of cost model projections. The largest cost category during the initial implementation would be the in-vehicle equipment cost required for network tolling ($655 million). The largest cost category for annual recurring costs would be the data communications function ($202 million).


System Elements
Capital (2008 Dollars)
Annual (2008 Dollars)
OBU (On-board unit) and installation
OBU / Installation – New Vehicles
OBU – Repair / Replacement
Training / Certification – Installers
Spare OBUs
OBU Subtotal
Stationary Stations
Transportable Stations
Mobile Stations / Vehicles
Enforcement Back Office
Enforcement Subtotal
Central System
Staff / Operations Training
Space for Central System / Back Office / Call Center
Central System Subtotal
Data Communications Subtotal
Other Subtotal
Grand Total

Traffic Choices Study - Summary Report

Traffic Choices Study - Summary Report
Publication Sort Date
Puget Sound Regional Council

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System Cost

Initial capital cost of network wide variable tolling system: $748,540,000. Annual O&M for network wide variable tolling system: $287,726,300.