Of course it is good for the economy that people can commute effectively. But by building more lanes we are choosing spread out cities dominated by highways where no one wants to live and instead drive to work from the suburbs.
And there are alternatives. We can choose more densely populated cities where the streets are dominated by pedestrians and people commute shorter distances mostly by public transport. Much better for the environment, and most importantly, better for people.
And we are making that choice whenever we chose between using the land for new roads or using the land for new pedestrian buildings and railways.
Comparing my apartment in Boston to mine in SF is like day and night. Here, I feel like I have my own place. It is a tad bit like a hotel room, but I don't hear much neighbor noise compared to the racket in Russian Hill.
Having a continual uneasiness due to random loud noises or having your own life impacted (listening to TV at a whisper, for example) is not human-friendly.
I think apartments get a bad rap because they are built with paper thin walls. It is more expensive to build with bigger spaces and proper noise control, but it has made a giant difference in my standard of living.
Please don't put out blanket claims like this and pretend they're obviously true, and then use them as justification for your particular view of how society should structure its geography. Some people hate densely populated areas. It would be utterly detrimental to my mental health to live in one. So if I have the choice to not live in an urban area, I'm going to take it.
I have a 45 minute commute each way every day to work. Long commutes suck. Living in the city sucks way more.
If moving from 30mph roads to 20mph roads reduced average traffic speed, then this would be a valid argument.
However, for most urban streets during the daytime the average speed is set not by the roads themselves but by the traffic capacity of the intersections along the road. It doesn't really matter how fast you can drive along a road if it only means that you get to the back of the queue for the next set of traffic lights a little earlier!
I commute-by-bike on a road with bike lanes in Somerville and Cambridge. At rush hour, no matter what the speed limit, the fastest way from point A to point B is a bicycle (unless A and B are stops on the red line), almost never exceeding 20mph. The reason cars are slow is that they take up too much space and have to wait in line, again and again and again.
I've seen this pattern in a number of "unintuitive and seemingly clever" traffic engineering tricks proposed in recent years. For example, it has been shown that removing all traffic signs can in fact improve safety -- again by slowing everyone down.
Another similar point (mentioned in the article) is that expanding freeways doesn't reduce congestion, because the new lanes are filled quickly. The argument is, apparently, that we therefore should not bother expanding freeways. The argument ignores the fact that the expanded freeway is serving many more people, creating immense value even if the speed of traffic hasn't improved.
(For the trolls: I personally take the train rather than drive whenever possible.)