In a place with consistent high population growth like Portland, induced demand would create congestion on 2, 3, 5, or even 10 lanes of road.
Investing in modes of transport where each person requires less space is the only way to have both population growth and not look like Houston or Dallas or Atlanta.
Like anything else, it's about tradeoffs. This series of planning decisions had a ton of downstream consequences, both positive and negative (and I'm happy to enumerate plenty of examples of either). I certainly don't enjoy the amount of traffic that has come with the city's growth --- I'm a lifelong Portlander, and have watched it happen --- but I firmly believe that more freeways would not solve the problem. Induced demand is a thing, and there is also geography to contend with. For example, one of the biggest traffic choke points is the freeway coming in to downtown from the western part of the metro area; since the 80s, there have been several major (one might even say "meaningful") projects that have widened it about as far as it is possible to go, but at this point there's literally nowhere else to put another lane. Of course, part of why it's a choke point is that after the tunnel it immediately intersects with another ill-sited freeway --- one of the last ones built before our "revolt," and one whose siting and construction caused logistical problems that the city is still dealing with, fifty years later.
Anyway, it's complicated, but the local government "betting the future on light rail" is not the reason traffic has gotten as bad as it has. Population explosion, geography, and seventy-odd years of path-dependent decisions about freeway placement and urban planning are the reasons.
I personally believe that part of the problem is Portland's style of government. There's a pretty good reason why it's the largest city in the US governed by committee. Though to be fair that may not really explain the whole problem. Just trying to design a replacement bridge across the Columbia cost 175 million without ever doing anything. Dysfunctional is an understatement for Oregon.
And yeah, "dysfunctional" only begins to describe the Columbia bridge debacle. But I will say, in defense of the project and its staff: that was a spectacularly challenging problem to solve. One of those fractal problems, where the more closely you look at it, the more complex it gets. The physical challenges were already going to be hard enough, and then the twelve-dimensional politics of the situation made it even more so. I don't pretend to know what the best solution would even be, but like everybody else in town I was disappointed to see it blow up after so much had been invested in it.
