It would have both economic and safety benefits if all states would legislate and enforce laws requiring the left lane to be used for passing only.

It would make traffic flow more efficiently for everybody which is both an economic and an environmental benefit.

By reducing the usage of the left lane for non-passing traffic, we would have less "road rage" for people who want to pass and less anxiety for those who want to drive slowly. This would reduce a major root cause for accidents.

Florida is getting tougher on this - but all U.S. states need to do the same:

http://alerts.nationalsafetycommission.com/2011/04/florida-keep-to-right.html

Drive safely. Drive smart.