The current pair of interstate bridges provides three lanes in each direction. One of the controversies over whether, and how, to replace them is to decide how big the replacement should be. Transportation advocates want the new bridge to be more than six lanes, because traffic demand is growing and requires a larger bridge; transit advocates and others want the new bridge to be limited to six lanes, because (if I understand their argument rightly) putting in more capacity would encourage suburban sprawl.
Let’s dissect that argument. First, a new bridge of 8 or 10 lanes would not encourage more people to move to the Portland-Vancouver metropolitan area, not even if it is of iconic design. People move here for jobs, not to look at bridges. The rate of growth will be about the same whether or not a replacement bridge has more lanes.
What it will affect is where the growth occurs. A bigger bridge will direct more of that growth to the Vancouver side of the river. A smaller bridge will keep more of that growth on the Portland side. Therefore, the advocates of keeping the replacement bridge to six lanes are saying in effect that Oregon’s farmland is less valuable than Washington’s farmland, and that sprawl belongs on the Oregon side and not the Washington side. They likely don’t know that they’re saying this, but they are.