IMO, Mini Metro is the far better game. In Mini Metro it always feels like the congestion can be solved, it's never hopeless... in Motorways the congestion does really feel impossible to work around, and then you lose. Not sure if that's due to my lack of skill or the difference between rail (discrete, must connect stations) and roads (continuous, can be drawn anywhere on the map)
Transport planner here. Haven't played either game, but it sounds like Motorways has an accurate model behind it. That's how the real world works, too.
c'mon man just build us one more lane, we can get you additional traffic flow next year, you know we're good for it just one more lane will fix all our the problems