To be more specific, I'm measuring throughput along road segments in a deterministic traffic simulation. Differences would occur when the user modifies the road network. The modifications often have no effect on most roads, but some wind up with more or less traffic than usual at a certain time.

I'm interested in showing differences like "during morning rush hour, there was more traffic here, but it was about the same the rest of the day", so I'm not sure a single correlation as a metric would be best. Ideally I'd plot two line plots and call out differences over time.