Seattle moves to new transportation level of service guidelines

By Robbie Webber

On January 14, the Seattle Council is set to vote on new regulations for developments to support changes in adopted transportation level of service. As part of the 2016 Comprehensive Plan, LOS was redefined to reflect specific target rates for different modes in eight different sectors in the city. The targets are to be achieved by 2035, and the single occupancy vehicle share is generally lower than the 2016 share in each sector. In order to achieve the 2035 targets, the city has drafted a new set of options that can be selected to reduce SOV trips.

The new regulations will change which development projects require transportation mitigation. Previously, many projects were exempt if they were not anticipated to affect traditional vehicle LOS on identified corridors. The new regulations require traffic mitigation measures to reduce SOV use for many more projects.

Options available to developers that must reduce SOV trips include:

  • Improvements to pedestrian facilities, such as new sidewalks and curb ramps, especially if the new facilities will connect to transit stops, shopping areas, and parks.
  • Transit passes for residents or employees. Not only will this encourage commuting by transit, but those receiving the passes will be more likely to use the passes for errands and social trips.
  • A mix of land uses to facilitate walking to nearby destinations.
  • Reduced parking for the building. Parking availability is a good indicator of the likelihood that trips will be made by car.
  • Additional options that may be proposed by developers to reduce SOV trips. Other cities allow mitigation options such as membership in bike sharing, shuttles to transit stops or employment centers, transportation information kiosks, bicycle education classes, parking cash out, etc.

In addition to mitigation to reduce SOV trips, the Seattle Council will also consider legislation increasing the minimum size of developments that are subject to a transportation impact analysis. Developments in the downtown and other designated areas close to high-quality transit would be exempt.

Seattle is the latest city to move away from traditional definitions of motor vehicle LOS and toward a more multimodal approach in assessing the impacts of new development. Different approaches to both modern traffic mitigation and performance metrics for developments can be found in the SSTI report Modernizing Mitigation: A Demand-Centered Approach.

Robbie Webber is a Senior Associate at SSTI.