Thais should be banned from hills and curves. I'm guessing brake fade/leaky hub oil seals , to lazy to change down a gear, air brakes should not 'fail' it is the air pressure that keeps the brakes off, when there is low pressure the brakes come on audio warning. But watching HGV being tested here, no steering check, no low air buzzer checked, no load applied when on a rolling road brake test. etc. etc.