[johnmwilkinson]

A peak of 4k/s does not mean they get that for the entire hour. The point I was trying to make is that simply computing the mean over a 24hr period will almost certainly ensure you size things incorrectly.

If a stretch of road was used by an average of 10 cars per minute over a 24 hour period, is it congested?

In both cases, you need more specific traffic data to size things properly.