The 2009 Legislature directed WSDOT to determine the potential for tolls to contribute no more than $400 million to construction funding for the SR 99 tunnel, and to analyze the impact of tolls on the performance of the tunnel. This tolling study (pdf 2.4 Mb) was released in January 2010. Additional traffic and tolling analysis is available in the project's Final Environmental Impact Statement.
WSDOT and the City of Seattle established the Advisory Committee on Tolling and Traffic Management in fall 2011 to explore ways to refine SR 99 tunnel tolling strategies. Decisions regarding the final toll schedule will be made by the State Transportation Commission and the Legislature before the tunnel opens, scheduled for late 2015.
Tolling scenarios
In our 2010 study, five toll scenarios were evaluated to determine if they could contribute up to $400 million in funding, while at the same time encouraging through trips to use the SR 99 tunnel, especially during peak travel times. The scenarios included a range of toll rates that varied by time of day and direction of travel. Some of the scenarios only tolled the tunnel, while others tolled the tunnel as well as trips using portions of SR 99 north and south of the tunnel to access downtown.
The lowest toll rate noted below was generally the overnight toll in our study; in most cases the highest toll was for drivers traveling southbound in the afternoon peak period.
| Toll Scenario |
Description |
Toll Range in 2015 Dollars* |
| Scenario A |
Medium tolls only for tunnel users
Designed to target the funding goal while also trying to balance diversion to other routes. |
One-way tunnel toll: $1.00 - $4.00 |
| Scenario B |
Medium tolls for tunnel and corridor users
Applies the same tunnel toll rate as Scenario A but adds a toll for drivers who only use the segments of SR 99 north and south of the tunnel to access downtown.
The segment toll would only be charged going into downtown in weekday mornings and out from downtown weekday afternoons. |
One-way tunnel toll: $1.00 - $4.00
One-way segment toll: $1.25** |
| Scenario C |
High tolls only for tunnel users
Designed to maximize revenues and, thus, toll funding. |
One-way tunnel toll: $1.00 - $5.00 |
| Scenario D |
Medium-high tolls for tunnel and corridor users
Applies tunnel toll rates that are between the rates of Scenarios A and C and includes a weekday peak-period-only segment toll on the portion of SR 99 south of the tunnel to the Spokane Street Viaduct.
The south-only segment toll was tested because of significant investments that will be made in this section of the corridor. |
One-way tunnel toll: $1.00 - $4.00
One-way segment toll: $1.50** |
| Scenario E |
Low tolls for tunnel users during peak periods only
Designed to help manage congestion during the peak period and minimize diversion of traffic at the expense of revenue generation. |
One-way tunnel toll: $1.85 - $2.80
No toll during off-peak periods. |
* Tolls vary by time of day and direction of travel.
** In scenarios with a segment toll, it was assumed users would pay either the segment toll or the tunnel toll, but not both. |
Our 2010 study assumed that medium and large trucks would pay a higher toll rate, similar to what is done on the Tacoma Narrows Bridge, and transit vehicles would not be charged a toll. However, carpools were assumed to pay, since, without an HOV lane in the SR 99 tunnel, there may not be a way to distinguish carpools from other vehicles.
How much toll funding could be raised?
The Office of the State Treasurer analyzed the toll scenarios in our 2010 study and found that Scenarios A, B, C and D would all closely approach, if not exceed, the $400 million maximum contribution directed by the Legislature. Toll Scenario E, which assumes low toll rates during peak periods only, would raise approximately $100 million in funding.
To fund construction of the tunnel, the State will borrow against future toll revenues in order to bring funding into the construction period. The State will issue bonds and pledge net toll revenues toward the repayment of principal and interest.