Spare air

Just watching one of the episodes, on cable.. A boss was telling Lisa that Hugh opened his company and that their company already had two (apparently) accidents, where some guys clearing the roads died. There was a shot of the vehicle falling through and water rushing in through the window, from the driver's side and onto a guy.

If there is real danger of going through the ice, why don't they carry diver's spare air with them?!??

Emergency air, wristband: http://www.noahi.com/secondbreath.htm && Spare air canister: http://www.spareair.com/