I-5 Operations and Demand Analysis

Interstate 5 (I-5) in Whatcom County is part of a 48,000-lane mile system of interconnected controlled or limited access highways that form part of the National Highway System. The original intended purpose authorized by the Federal Aid Highway Act of 1956 was “to provide for safe, efficient, speedy transcontinental travel and serve a strategic National Defense purpose”. The Federal Highway Administration, along with the Washington State Department of Transportation (WSDOT), is responsible for this system and recognizes that the Interstate System is not only a part of the National Highway System, but is also a part of regional and local transportation systems.

In 2017, WSDOT began a statewide planning process with our partners (Corridor Sketch Initiative) to evaluate the entire state-owned system and determine where things are working well and where changes may be needed. Within Whatcom County, the evaluation revealed that mobility and fish passage barriers posed the greatest challenges on I-5 from Fairhaven (SR 11) to Grandview (SR 548).

This I-5 Operations and Transportation Demand Management Analysis found that I-5 does have significant congestion during peak travel periods, but does not suffer from a capacity problem. I-5 does, however, suffer from an access problem. Over 50% of the traffic in the Analysis Area between Samish Way (exit 252) and Bakerview Road (exit 258) travel less than three interchanges in distance on I-5. This means that over half of the travel on I-5 is less than 3 miles in length, and all of that entering and exiting traffic creates significant disruption and friction on the system. Where feasible, metering the on-ramp traffic would create gaps making it easier to get onto and off of I-5, improving safety and regional traffic flow.

Congestion caused by such a large percentage of short trips by itself poses a significant challenge to all drivers, but the correlation to crashes is the most serious problem that the Analysis discovered. Shifting this local traffic from I-5 onto local city streets, which also exhibit significant congestion, would be problematic without meaningful travel demand management actions and improvements to transit and the active transportation system (walking and rolling).

To address the identified mobility and safety needs on I-5, the significant barrier to walking and rolling that I-5 imposes on the local network, and to facilitate the City’s attainment of mode shift and emission reduction goals; we are recommending three distinct yet interrelated strategies and alternatives. Focus Area #1: Interchange Operation and Safety Enhancement Improvements (low cost traffic management improvements); Focus Area #2: Ramp Metering and Traveler Information Signs, (primarily during peak periods of congestion);  Focus Area #3: Lincoln-Lakeway Multimodal Transportation Study (currently underway led by the City of Bellingham). These actions meet the Washington State Legislature’s policy direction to WSDOT to plan for state-owned facilities which specifically require WSDOT to first assess strategies to enhance the operational efficiency of the existing system before recommending system expansion.

Focus Areas #2 and #3 will involve significant community engagement as these strategies and solutions are considered for inclusion into regional and local plans, and ultimately for funding.

The overall results of this I-5 Operations and Transportation Demand Management Analysis found that transportation systems management and operations (TSMO), travel demand management (TDM), maintenance, preservation and environmental stewardship are all necessary to meet the policy direction found in the City of Bellingham’s mode shift goals, and the Climate Protection Action plan, Washington State goals for emissions reduction and WSDOT’s Sustainability Executive Order.