RSD Phases 1 and 2
- Z-factor Consultation
- Nov 12, 2020
- 2 min read
Reduced Stopping Distance was implemented in phases, generally known as RSD1 and RSD2. The Federal Mandate was aimed at making roads safer and began in 2011 with what is known as the typical tractor. The largest impact group comprised the first phase. Each OE had to perform testing and document the tested configurations.

Phase 1 included 3-axle tractors: under 59,600 lbs. GAWR. The goal was to reduce the stopping distance from the regulated 355 feet, to 250 feet. This was an aggressive decrease, but we saw very few changes in 2011, because most tractors in the category already stopped far shorter than the government mandate. Some OEs eliminated things such as 15x4 inch front brakes, and spring brake deletion on one of the tandems.
Phase 2 enlarged the group of vehicles required to stop in 250 feet by including 2-axle tractors and 4-axle tractors rated under 85,000 lbs. GCWR as well as Heavy 3-axle tractors rated under 70,000 lbs. GAWR. It also established a reduction of 45 feet for 4-axle tractors over 85,000 lbs. and Heavy-Heavy tractors rated over 70,000 lbs. GAWR. This group of chassis was much more diverse.
Diversity made implementation of Phase 2 much more challenging and required more visible changes. Brake suppliers changed materials, OEs required larger brake sizes, long stroke chambers, and in some cases 6S/6M ABS. OEs can only sell configurations that have been certified. Due to the vast customization of heavy-duty trucks, it was impossible to test every iteration of the vehicle configuration. OEs decided based upon history and forecast, the reasonable testing group. In the end, if a configuration was not tested, it cannot be sold.
The result of this is a small group of chassis we have run in the past, we know are compatible, but OEs no longer build because the configurations were not included in the test groups. This paring down really needed to occur to make the project manageable, and in reality, with a few reasonable component changes your previous vehicle can still be built. If you run up against this, speak to Engineering to see what changes can be made to update your chassis to a certified configuration.
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