Don't know if this has been covered before, or not, but I've been on the telephone for the past two days trying to find out what I have to do to comply with Oklahoma's trailer lighting requirements. Turns out our State just uses the Federal Gov's requirements. I finally found the following site and boy is it helpful. Hope it helps you also.
http://www.nhtsa.dot.gov/portal/site/nh ... e=standard
(God, I didn't realize it was so darned long!)