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Judging IBR Climate Impacts: The importance of an investment grade toll analysis

    Climate, Equity and Environment are among the key guiding values for our Alliance. So how do we judge the climate impact of this project? We’re paying attention to vehicle volume. There are two ways of expressing that, either as Vehicle Miles Traveled (VMT) or as Average Daily Trips (ADT). 

    When it comes to the IBR, three factors will drive VMT/ADT:

    • Transit Availability. Getting high capacity transit across this bridge is critical and one of the reasons the Alliance wants a successful project. The project team is already claiming 36,000 metric tons of carbon saved every year from this.
    • Induced Demand. Call them what you will: auxiliary lanes, ramp-to-ramp lanes or merge/weave lanes, the project will add a new lane between Marine Drive and Mill Plain in each direction. This is new capacity that will lead to more driving.
    • Tolls. Tolls will inevitably suppress demand for driving. How much reduction in driving will be a function of the price level and time-of-day patterns for pricing. Pricing to pay for the project may look different than pricing specifically aimed at managing congestion.

    Unfortunately, the project has yet to give us a forecast of either VMT or ADT. Instead, when asked about climate, project leaders give us the following talking points: 

    • Construction techniques. The project has said that they will be using state-of-the art low carbon constructions techniques. We appreciate that, and good for them! But those carbon savings will be dwarfed by the impacts of the vehicles driving over the bridge over its lifetime. So let’s keep our eyes focused!
    • Relieving stop-and-go traffic. This is basically a myth. By one estimate, it only takes a 2% growth in traffic to overwhelm any savings from idling traffic. And induced demand will lead to congestion returning before long. Again, focus on the vehicle volumes!
    • Electrification. We believe electrification of the vehicle fleet is vital. But we’re also cleared eyed that it simply can’t happen fast enough to get to the kind of carbon reductions we need by 2030 or 2040. We have to have immediate, significant mode shift away from single occupancy vehicles. 

    The critical questions for IBR project leaders are how will these factors interact and will the net result be more driving or less? 

    An investment grade toll analysis would inform how transit, auxiliary lanes and tolls would interact to affect vehicle volume. It would also inform the community about the range of toll rates that will be needed to fund this project. This is why we would like an investment grade analysis to be done in time to inform the environmental review, NOT just before tolling is implemented.