> "Traffic congestion is caused by there being too many cars on the road with limited space for cars."

I mean in some sense this is always going to be true, and removing cars will always help alleviate traffic. But it's not true that driving behaviour is not a significant cause of traffic congestion: it's the cause in most cases. [1]

For an extreme illustration, there's a well-known phenomenon where adding extra lanes of traffic to a highway or freeway actually worsens traffic: the added bandwidth interacts in weird/subtle ways with driver behaviour. [2]

[1] https://www.vox.com/2014/11/24/7276027/traffic-jam

[2] https://www.wired.com/2014/06/wuwt-traffic-induced-demand/