“Can our drivers sleep in their vehicles overnight whilst they’re loaded with dangerous goods?”

In most cases with Hazard Classes 2, 3, 4, 5, 6, 8 and 9 the answer is yes, they can but there are a couple of examples to note:

In vehicles loaded with Class 7 Radioactive materials it is prohibited, as damage from radiation is increased through prolonged exposure to radioactive materials so to unnecessarily increase the time of exposure by sleeping in the vehicle would be highly inadvisable.

Carriers might also take a best practice view with regard to vehicles loaded with dangerous goods carrying a toxic risk, and in the gas of toxic gases in particular there is a prohibition using vehicles with a shared load space / driver’s cab atmosphere i.e. a panel van.