Statistically, internationally this hasn't worked. If you build more roads, the traffic situation improves, then more people use their cars, and you are back at the same level of congestion as before, a couple of Rbillion later.
Yes but all those extra cars consume more fuel which generates taxes in fuel and licensing for the government.
With your reasoning we would still have a single lane highway between JHB and PTA.
All that does is it stops cities from growing and forces urbanisation to spread out over larger areas.