The queuing theory to work out the solution gets very complicated (far more complicated than I can be bothered with for a Slashdot post). The distance between the cars is probably enough (although you'd want some margin for error) if they're all staying one breaking distance apart, but they'd also need to make sure that they are either regular, or that the streams in each direction have the same gaps. That's going to require some rearrangement on the road, which will lead to the ripple effects that the grandparent mentions. And, if there are going to be human inhabitants in the cars, then you will still need them to decelerate if they're turning, rather than just crossing.