Wait, are there 1000 people going to work, and then the car parking outside of work? Or are those cars leaving where the people work to go elsewhere? the later creates more cars on the road. Sure those 1000 cars can go somewhere to park - but now we can't build much denser as we still need parking for the cars. Maybe we can move the cars out a bit for more density where people work, but then we need roads to get those cars back out.