The AAMVA CDL Manual explains that 'outage' requirements differ between liquids. What is the stated reason different liquids require different amounts of outage?

Question

Accepted Answer

Different liquids expand by different amounts as they warm, so varying amounts of empty space must be left in the tank

Answer

Denser liquids are more flammable and need more headspace for ventilation

Answer

Outage amounts are set only by the shipper's insurance policy, not by the liquid's properties

Answer

All liquids require the exact same outage; only hazardous materials require any outage at all