If the current I-5 Bridge is replaced by a new “high volume” bridge, where will all the cars go once they’ve crossed the Columbia? Highway 99 and I-5 in Oregon are already very slow. The entire landscape south of the river would need to be redone to provide more roadways for increased traffic.
On the Washington side a new route to relieve Highway 14 would be needed.
A new bridge alone will not solve much.
Someone smarter than me needs to sit down and lay out roadways that could handle a “high volume” of vehicles and that plan should be melded with the plan for a new bridge.
With that in mind, I say any new bridge must also carry light rail. A rail line that runs through Vancouver from the I-5/205 split to downtown Portland would be a good complement for moving traffic before and after it crosses a new bridge.