By WSDOT, SDOT, King County Metro, Sound Transit

One month after tolling began in the State Route 99 tunnel, we’re getting our first few weeks of traffic data. While it’s still early, SR 99 tunnel usage remains high and exceeds forecasts. Traffic volumes were within normal ranges on I-5 and ridership on King County Metro Transit remained consistent.

Initial information from Seattle-area transportation partner agencies reflects weekday data between Nov. 12 and Nov. 22. (Thanksgiving week was excluded as it is an unusual travel week). Traffic patterns vary and we expect they will continue to change as drivers look for best routes to reach their destinations.

By the numbers
Prior to the start of tolling on Nov. 9, 2019, about 77,000 vehicles used the tunnel on average weekdays. Since tolling started, roughly 20,000 fewer vehicles are using the tunnel – about 26% less. This drop is less than the 35% to 50% predicted. However, the story is more nuanced. Peak travel volumes in the tunnel remain high. Mid-day volumes are lower, likely due to less crowding on city streets.

Where is traffic going?
The traffic story is evolving. As expected, week one looked different than week two. Volumes have increased on city streets near the tunnel, but to date, travel times and reliability are not greatly impacted.

For example, traffic volumes on Alaskan Way increased by about 20% in the first two weeks of tolling, the equivalent of about 5,000 more cars, but travel times increased just 3% to 4%.  Traffic volumes on First Avenue also increased in both directions, yet travel times slightly improved.

In week one, we observed increased volumes on Alaskan Way in both directions during the morning and afternoon peaks, as mentioned prior, and along Elliott Avenue West northbound during the morning peak varying from 25% to 30%.

In week two, we observed the same volume increases along the waterfront, plus higher northbound volumes in the evening through SODO on Airport Way, East Marginal Way, and Fourth Avenue South, from between 20% and 25%.

It’s common for traffic volumes on Seattle streets to fluctuate up to 20% on any given day. Therefore, depending on the street and time of day, some drivers may or may not notice more cars.

Fluctuations are typical on urban freeways. The number of vehicles using I-5 during the first two weeks of tolling on SR 99 were within the normal ranges for this time of year. There were some days when people experienced longer travel times during the morning and afternoon peak periods. This can be attributed to a number of factors including weather – people tend to drive slower in wet conditions – blocking incidents such as collisions or stalled vehicles, and even special events.

We continue to urge commuters to check the roads before you leave by using  WSDOT’s travel toolsSDOT’s travel tools or other traffic apps.

During the past year, Metro ridership has generally increased on the 41 routes affected by the SR 99 tunnel project. Transit ridership has remained stable during the first two weeks of tolling.

Looking at the past year, Metro’s ridership changes on affected trips varied somewhat by route. Route 40 average weekday ridership climbed from an estimated 12,440 in November 2018 to 14,330 in November 2019. Meanwhile, Rapid Ride C Line dipped slightly during the same time period ­– 12,050 to 11,710. (Not all buses have passenger counters, and ridership estimates are based on extrapolations of available samples.)

Additionally, the RapidRide C Line and 11 other former viaduct routes have experienced disruptions and changes in pathways in the past year. Since the viaduct closed in January 2019, average peak hour travel times are longer than they were in 2018, and fluctuate daily based on peak traffic congestion.

Between October and November 2019, average transit trip times increase slightly during the morning and afternoon peak hours:

  • Morning inbound travel times on average were unchanged for Route 120, 1.5 minutes longer for Rapid Ride E Line, 2 minutes longer for routes 40, and 3 minutes longer on Route 131.
  • Afternoon outbound travel times on average were less than 2 minutes longer for Route 120, nearly 4 minutes longer for Route 131, and 5.7 minutes longer for Route 62, and 2 minutes longer for Route 40.
    Factors other than tolling might partially explain these travel time increases.  Fewer hours of daylight, increasing ridership, weather conditions, and other factors also affect bus speeds.

No information is available for Link or Sounder usage.

Water Taxi usage and bike usage
Since 2018, King County Water Taxi has been steadily increasing ridership, and comparing November 2018 to November 2019, there were about 400 more weekly riders each on the Vashon Island route and the West Seattle route. Water Taxi ridership before and after tolling is stable.

Dry weather and improved bike infrastructure made biking a good travel option during   November. As captured by four counters on paths in and out of the Center City – which encompasses South Lake Union south to SODO and east to Capitol Hill – bike ridership was 25% higher than the previous year. In 2019, we only experienced on 1.72 inches of rain compared to 5.42 inches in 2018. And Seattle’s network of protected bike lanes though the Center City grew.

Map of Center City Protected Bike Lanes

Good To Go!
One final observation: Roughly 80% of vehicles in the tunnel are using either a Good To Go! pass or Pay By Plate. Drivers with a Good To Go! pass will always pay the lowest toll rate in the tunnel and all other toll roads in Washington. Even if you used the tunnel without an account and received a bill in the mail, it’s not too late to save money on your bill by creating an account and having the reduced rate applied retroactively.

The SR 99 tunnel is a two-mile long, double-decked road tunnel that carries SR 99 underneath downtown Seattle. It replaced the seismically vulnerable Alaskan Way Viaduct, which used to carry SR 99 above Seattle’s waterfront. State law required WSDOT to use toll revenues to pay back $200 million in construction bonds, as well as pay the costs of operating and maintaining a safe tunnel.