Seattle should be ashamed at giving themselves 10 years just for planning + design. This isn't the linear shinkansen, you're not even crossing state lines! It is a train. We know how to do this.
There are obviously considerations to optimise for but how do you need 5 years for planning, _then another 5 years for design_?
Modern civil engineering is extremely inefficient. In a software system, for instance, you design largely by “instinct.” You’re given a problem, you consider a the pros and cons of a few possible solutions, and then commit to one based on these considerations. Civil engineering doesn’t work like that. For something like a road or a railway, they’ll split it into pieces and then consider every possible way of construction along each segment, including studying things like environmental impact. It takes a ridiculous amount of time and effort. Part of the reason for this is so that when people sue to block construction they can say they considered all the other alternatives.
I agree that they should do it more quickly, but they aren't just building this line, they're building light rail lines throughout all of Seattle and the suburbs. There's a giant master plan that goes 25+ years all the way out to 2050ish.
It’s been a lot longer than 10 years. The empty, massive, underground bus/train “depot” that sits under the downtown has multiple track gauges running through it from all the failed projects.
There are obviously considerations to optimise for but how do you need 5 years for planning, _then another 5 years for design_?