When the speed limit’s 50 km/h or less and there is good visibility, you do not have to place a warning triangle. You should place the warning triangle at preferably 100 metres behind your car, but not less than 50 metres so that other vehicles are prepared for the danger ahead and are ready to act accordingly. The exact distance also depends on the situation, for instance if there is a sharp curve 100 metres behind your car, then it’s probably better to place it for instance 150 metres behind your car so that traffic can see the triangle already before entering the curve.