I was so conflicted on this initiative. I live out in the Enumclaw / Maple Valley area, and the roads out here have seen pretty much zero expansion in capacity in the last 30 years. Yeah, they've added a lane in places to 169, i.e. the four-corners area of Maple Valley, but that does nothing to actually increase capacity north bound when there are miles of road that are still just two lanes. Highway 18 is still the same death trap it has been for decades, and there are really no other alternatives if you want to go north bound.
I think the problem most people have is that they see these high gas taxes and car tabs, and have no idea where that money goes. In my case, I see zero evidence of any of that going to help my commute in the last 30 years despite massive population growth and traffic out here, so why would I support more of it? People are obviously willing to pay for improvements, i.e. ST3. Show us what we have purchased with that money.
Likewise though, with this initiative apparently passing, I suspect we will now see an increased push for an alternative pay-by-mile type system. I see that turning into something similar to the 405 tolling lanes, with expensive outside monitoring and a questionable at best return to the tax payers.