i believe all three use the same ratings system now.
The new standard lays out minimum performance standards for acceleration, braking and handling. There are parking brake tests and grade-launch standards. The trailers used to conduct all such tests are spelled out specifically, and they must be ballasted and connected in a specific way.
And J2807 sets a minimum speed for the truck-trailer combination when climbing a specific mountain grade — the so-called "Davis Dam" grade that climbs eastward out of the Colorado River valley at Laughlin, Nevada. Cooling systems must bear the strain of the 11-mile trip when the outside temperature is at least 100 degrees and the air-conditioner is set to full blast.
