Based on the antennas I see on the trucks here they are on VHF. I know about a year or two ago they put up a new tower on a mountain here.
This is what is listed in the database (stilltitled as highway and transportation dept which is their old name... that needs to be updated to Arkansas Dept of Transportation since their name changed (
@milf)).
Scanner Frequencies and Radio Frequency Reference for Department of Transportation (ARDOT) (Arkansas)
www.radioreference.com
Try plugging those in and see what you hear. It matches the antennas and radios they run since by all appearances they have conventional radios with vhf antennas.