On November 11 I posted a blog about portable, rolling signs that were on both sides of I-65 with lights spelling out info on what appeared to be a private car show. I sent this information to Kate Howard, otherwise known as Ms. Beep, with the Tennessean. No one with the Williamson County Ag Expo Center where the car show was being held, the Williamson Co. planners, Williamson County highway department, or the parks and recreation departments, which hosted the event, admitted knowing anything about the signs. Ms. Beep checked with TDOT and was told electronic signs are put up for events drawing 50,000 or more which might cause traffic problems (think Bonnaroo), but the signs I saw were not approved. TDOT representative said had they known about the signs, they probably would have been removed for safety sake.
So, if you see portable, rolling signs on the interstate right-of-way, it may be that they aren't authorized and are there illegally.