"The concept is called induced demand, which is economist-speak for when increasing the supply of something (like roads) makes people want that thing even more. Though some traffic engineers made note of this phenomenon at least as early as the 1960s, it is only in recent years that social scientists have collected enough data to show how this happens pretty much every time we build new roads." https://www.wired.com/2014/06/wuwt-traffic-induced-demand/
What's Up With That: Building Bigger Roads Actually Makes Traffic Worse

The concept is called induced demand, which is economist-speak for when increasing the supply of something (like roads) makes people want that thing even more. Though some traffic engineers made note of this phenomenon at least as early as the 1960s, it is only in recent years that social scientists have collected enough data to show how this happens pretty much every time we build new roads.

WIRED

@freakonometrics
The phenomenon was observed by Lewis Mumford earlier…

In 1955, urban observer Lewis Mumford wrote a series of essays in the New Yorker titled “The Roaring Traffic’s Boom,” in which he memorably compared a highway planner widening a congested highway to “the tailor’s remedy for obesity — letting out the seams of trousers and loosening the belt. [T]his does nothing to curb the greedy appetites that have caused the fat to accumulate.”

From: https://www.bloomberg.com/news/features/2021-09-28/why-widening-highways-doesn-t-bring-traffic-relief

Why Widening Highways Doesn't Bring Traffic Relief

U.S. transportation authorities have spent billions widening urban freeways to fight traffic delays. What makes the “iron law of congestion” so hard to defeat?

Bloomberg