dude you are lucky to get away with just 500 riyals fine...my friend got 900 riyals fine and 4 points for over speeding..haha...anyways you just don't need to be careful to maintain speed below 80kmph when crossing the signals , u need to maintain the speed even on the normal roads equipped with camera...and you can't do anything about this kind of fine..they don't listen ..some how its good...the only way to maintain peace on doha roads..lol