Unmarked p/u truck on a bridge taking pictures of all westbound traffic….up to 10 chase cars….ongoing activity. As you leave GA the speed is 70mph….at the AL border there is a temporary lighted sign with small letters indicating 55mph, but difficult to see because the sun is reflecting off the sign and you are driving 70mph speed. One expects this type of sign to provide roadwork activity info. No construction activity in either direction…go figure. 70mph is posted later in the Anniston, AL area on the same interstate hwy.