Source: The Congestion Con: How more lanes and more money equals more traffic (37-pg PDF)
"In an expensive effort to curb congestion in urban regions, we have overwhelmingly prioritized one strategy: we have spent decades and hundreds of billions of dollars widening and building new highways. We added 30,511 new freeway lane-miles in the largest 100 urbanized areas between 1993 and 2017, an increase of 42 percent. That rate of expansion significantly outstripped the 32 percent growth in population in those regions over the same time period. Yet this strategy has utterly failed to “solve” congestion."