Cars are expensive, so poor people usually rely more on public transit like busses, which get stuck in traffic behind cars. Driving more is positively correlated with higher income.
Lower income people disproportionately suffer the consequences of the current car-centric system like air pollution, noise pollution, traffic violence, etc.
This feels like a totally theoretical idea, or one from a place very different from the US. I think a lot of posters here are from the US where having a car is almost mandatory and you'll only take the bus if you're literally too poor for a car. Most low income people in most US cities can afford cars, it's just a massive burden, but without a car they would have so much less time because transit is bad.