What I-912 will do to Seattle-Bellevue travel
Interstate 90 from Seattle to Bellevue was built with high capacity transit in mind. The express lanes through the center are reversible, efficiently serving the direction they are pointing, but worsening traffic in the direction they are not. As population grows (and SR-520 doesn't), traffic density is increasing on I-90, and WSDOT and Sound Transit are working together on a solution.
Sound Transit's High Capacity Transit Analysis Summary (PDF) shows that the best cost per rider solution for I-90 is HOV bus rapid transit, followed by light rail integrated with the Central Link system as rider demand increases. Do note that Sound Transit's <$10m cost estimate for HOV bus transit is misleading, because WSDOT is paying for the HOV lanes. In order to run light rail on the central express lanes, however, dedicated HOV lanes will have to be built for the existing traffic.
In four phases, WSDOT will widen the roadway and add outer HOV lanes with dedicated entrances and exits to both travel directions. This will remove bus transit from regular travel lanes and create more highway capacity, as well as make bus service more reliable over the bridge - increasing ridership, and lowering the number of cars in the regular travel lanes. The first phase, including direct HOV access ramps from I-405 South to I-90 West, is funded by - you guessed it - the 2005 Transportation Tax Package.
Initiative 912 will eliminate funding for better bus service and reduced traffic in the non-express direction, and it will delay or cancel plans for high capacity transit to Bellevue. This is bad not just for the tens of thousands who commute on I-90, but for everyone who depends on goods delivered via I-90. Local food and raw materials as well as many of the goods we ship overseas depend on truck transport through this corridor. Adding thousands of unnecessary cars per day will cost shippers more and waste billions of dollars worth of work time.