You can't assume that the number of cars is a constant though. As point A and point B become farther apart, car usage goes up. When they become closer together, car usage scales down.
If your mailbox is attached to your house, you can lean out your front door to get your mail. If your mailbox is at the end of your 20 foot driveway, you take a few steps to get your mail. If you live on a farm, and your mailbox is down a several hundred yard driveway, you might hop in your side-by-side UTV. If your mail goes to a Post Office Box in town, you might hop in your truck and pick it up while running errands.
https://en.wikipedia.org/wiki/Jevons_paradox
If things that had been a 10 minute drive become a 5 minute drive, now they're worth it when before they weren't. You go to the shop instead of waiting 2 days for Amazon. You go to the shop you like more instead of the one you like less even though the lesser one is closer, because now the difference isn't as big.
If you make the drive shorter but make parking harder,
and you make the walk/bike shorter but walking/biking pleasant,
people will take their cars less.
As traffic and travel times lessen, people do travel further and more, but only to a point.