In Seattle I noticed that traffic is always light on Monday, but some places get jammed other days of the week. Apparently, there are many people who don't have to be somewhere on Monday, and those same people chose to drive during rush our on other days of the week. What's up with them anyway? If you don't have to go to work, why drive anywhere during rush hour?
It could be that people with somewhat flexible schedules end up going into work later or earlier on Monday than average, spreading out the traffic enough to keep it moving fast.
Also, it could be that there are people who don't normally work on Monday, which is actually fairly common in many service industries. Many restaurants are often closed on Mondays, for example.
Moreover, more Mondays and Fridays are taken off either for "sick" leave or vacation. It may only take a small percentage to make a noticeable impact on traffic flow.
