It shows the short term advantages of adding a lane. It pays no mind to what sort of development the new, higher traffic flow will bring, and how that will eventually doom that third lane addition to be just as congested as before. The solution isn’t adding more capacity to roads, it’s getting more people and things off the roads and onto alternative means of transportation.
Make alternative means better (chiefly faster or overall cheaper) and people will adopt them. People might not all be geniuses, but they’re not stupid.
You're assuming that satisfying demand is not a good. You're also arguing that we should wear a hair-shirt until the rapture. (If the alternatives can't compete with relatively good traffic, if they're only used when nothing else works, how good are they.)
> On the other hand hitting Georgia on 95 south really shows the advantage of adding a third lane. Hard to argue with that example.
Road widening projects are usually pretty easy to argue against, though winning these arguments is usually based on emotions and political clout and not an actual rational perspective.
A couple questions that are always good to ask is:
1) When the road was built or last expanded, was it clogged with drivers right away?
2) Does the extension narrow back to fewer lanes at some point?
Give any road extension a couple of years and drivers will be asking for an additional lane on that same road, and/or you’ll be moving the target to the next ‘bottleneck’ down the line.
So why have two lanes over 1 lane? If you have two roads merging for a few miles then splitting, going to one lane will cause a bottleneck
Obviously there is a point where an extra lane is useful and a point where dropping a lane is useful.
Other questions you ask - when the road was built did traffic in nearby roads drop, did you get fewer cars rat-running through residential areas, is the increased traffic because of closure of rat runs making travel in the congested freeway more attractive despite the lack of capacity.
There’s other long term questions too, did the freeway allow people to live further from their destination, encourage longer or more frequent journeys, although the answer to that could be positive or negative depending on your viewpoint. Eventually you get to asking “is the motor car a good thing or a bad thing”.
On the other hand hitting Georgia on 95 south really shows the advantage of adding a third lane. Hard to argue with that example.