Nebraska Department of Roads Carrier Enforcement Officer "Red" Hall who worked the A-Troop area in the 70's & 80's only had a 39.9 Motrac and a Plectron monitor on 42.46 mHz. in his cruiser. His primary communication points of contact were with the Cass, Sarpy and Douglas County Sheriff Departments on 39.9 mHz. Red was a unique character who had the ability to know if a truck was overweight just by hearing the noise from the tires of a passing rig. He never missed.
If NSP Omaha needed to contact him, they would usually just telephone the Douglas County Sheriff and the dispatcher would relay the traffic to him on 39.9
The NDOR Carrier Enforcement Officers at the Greenwood scales also had 39.9 radios and they communicated primarily with Ashland, Wahoo, Plattsmouth and Papillion. NSP was very touchy about who transmitted on their frequencies back in the good old days.