The Georgia State Patrol and the Motor Carrier Compliance Division both fall under the Georgia Department of Public Safety.  Officers of both are POST-certified officers.  Traditionally, MCCD deals with motor carriers, i.e. commercial motor vehicles, and GSP deals with all traffic laws. Commercial motor vehicles is actually a bigger area than many people are aware.  I have had plenty of drivers of bigger pickup trucks pulling bigger trailers startled to find themselves ticketed for not having a required CDL. 

While MCCD is directed by statute to focus its attention on motor carrier issues, it is expressly not forbidden from general traffic enforcement.  So, if a MCCD officer sees you speeding in your Honda Civic, they are not required to ignore it.  They can pull you over, and they can give you a ticket.

Usually, there is enough commercial traffic to occupy their attention, but one should not count on that.

For those that are interested, the jurisdiction of the MCCD is outlined at OCGA 35-2-101.