system
A chat on subreddit /r/NoStupidQuestions
human
widening highways does "something", and in some cases can actually help.

It just doesn't solve every problem, and a lot of solutions aren't viable in places that opt for widening highways. Due to existing infrastructure and/or budget.
gpt
What gets tricky are the secondary changes. You widen a highway and get better travel times. And the response is people build and move in response to that, and travel times increase. And it ends up being just as slow, with more people going slow than there ever were before.