Here are the regulations if anyone wants to know. Unless your tractor weighs over 10,000 lbs follow the rules under 393.128. The top two paragraphs are a summary of the two regulations that apply for tractors. The bottom paragraph is the regulations that apply to must of us with a compact tractor that weighs less than 10,000 lbs.
Cargo Securement Rules | Federal Motor Carrier Safety Administration
393.128 - Automobiles, Light Trucks and Vans
This portion of the new standards applies to the transportation of automobiles, light trucks, and vans which individually weight 4,536 kg (10,000 lbs) or less. Vehicles which individually are heavier than 4,536 kg (10,000 lbs) must be secured in the same manner as heavy vehicles, equipment and machinery (see the rules under /393.126).
393.130 - Heavy Vehicles, Equipment and Machinery
These requirements are applicable to the transportation of heavy vehicles, equipment and machinery which operate on wheels or tracks, such as front end loaders, bulldozers, tractors and power shovels and which individually weigh 4,536 kg (10,000 lbs) or more. Vehicles, equipment and machinery which is lighter than 4,536 kg (10,000 lbs) may be secured in accordance with these rules, the rules for automobiles, light trucks and vans, or the general freight requirements.
§ 393.128: What are the rules for securing automobiles, light trucks and vans?
(a) Applicability. The rules in this section apply to the transportation of automobiles, light trucks, and vans which individually weigh 4,536 kg. (10,000 lb) or less. Vehicles which individually are heavier than 4,536 kg (10,000 lb) must be secured in accordance with the provisions of § 393.130 of this part.
(b) Securement of automobiles, light trucks, and vans. (1) Automobiles, light trucks, and vans must be restrained at both the front and rear to prevent lateral, forward, rearward, and vertical movement using a minimum of two tiedowns.
(2) Tiedowns that are designed to be affixed to the structure of the automobile, light truck, or van must use the mounting points on those vehicles that have been specifically designed for that purpose.
(3) Tiedowns that are designed to fit over or around the wheels of an automobile, light truck, or van must provide restraint in the lateral, longitudinal and vertical directions.
(4) Edge protectors are not required for synthetic webbing at points where the webbing comes in contact with the tires.