Here is another fact to ponder, of the newer cars out on the road, many are hybrids that perform much worse in winter driving conditions. In order to keep gas mileage up many drivers may be driving in a way where they operate more on battery power than on gas. Combine this with all of the old cars with bald tires, and people that just should not be driving anyway and traffic will slow down.

I am usually driving about 60-65 and I am never in the left lane. I do it to keep my RPMs down and my MPG up!