You're driving a placarded tank truck carrying a Class 3 flammable liquid and need to stop briefly on the shoulder of a two-lane highway because of a mechanical issue. How close to the traveled portion of the roadway can you legally park?

49 CFR 397.7(b) (parking restriction — hazardous materials other than Division 1.1/1.2/1.3); AAMVA CDL Manual Sec 9.6.2, 'Parking a Placarded Vehicle Not Transporting Division 1.1, 1.2, or 1.3 Explosives' (nhcdm.pdf p.9-13)

Parking within 5 feet of moving traffic puts your rig, and any hazardous load, directly in the path of passing vehicles. A collision with a hazmat trailer that close to the road turns a minor mechanical problem into a multi-vehicle hazmat incident. The rule forces you to get fully off the road before stopping, even if that means driving a bit further to find a safe shoulder, lot, or rest area.