The one way systems in old cities that are not built on a grid pattern can be quite complex. They are put in place because the street concerned is too narrow to take the modern traffic density. I am sure I've seen something like this in Boston, Mass. Originally there would have been only the one major street, built for horse and carriage, running along that route in the city so if that street is made to take a one way traffic flow then the return flow has to use a variety of minor roads and if you miss the signs you could get lost. I don't think you could properly call it a divided highway, that sounds more like what we would call a dual carriageway - that is a major road with a central reservation.

Vive la difference!