Kansas Highway Patrol trooper and Public Information Officer Nick Wright wrote in after hearing my podcast discussion with Andy Blair, a compliance safety consultant and former inspector himself, that first aired last Friday. Blair and I spoke chiefly about the out of service criteria as they relate to the truck and trailer's air brake system, with Brake Safety Week then upcoming and now ongoing.
Wright wanted to clarify a few of the points discussed in the podcast, including how the out of service criteria work when it comes to combination vehicles. Blair described the interplay there accurately in general terms, though our discussion was incomplete in that it failed to make clear the reality of how roadside/weigh station inspectors are required to treat a combination unit when it comes to the 20% rule for out-of-adjustment brakes. (To simplify, for those who missed the original post: If 20% or more of a vehicle's brakes are out of adjustment by a quarter-inch or more, the vehicle is out of service -- and you can also get there with a series of "half brakes," where a brake is just 1/8-inch out of adjustment.)
[Related: Inside the 20% rule -- Out of service brake adjustment, other violations, and how to prevent]
As Wright emphasized (and I updated the original post with a brief note here to reflect this), "the 20% rule is calculated on all brakes on the combination as it comes to us, meaning at the time of inspection," he said. On a typical five-axle tractor-trailer combination, "it takes two brakes, however you get there," to put a combination out of service. "All vehicles that contribute to the 20% must be declared out of service."
Wright gave the example of a set of triples with "a lot of brakes and six different units" undergoing a Level 1 inspection:
In such a case here's what the inspector would be looking at:
The 20% out-of-service criteria for adjustment alone would "kick in at four defective brakes," Wright said, whether "four full brakes, eight half brakes or two full and six half, etc."
