One easier way is traffic light controlled pedestrian crossings. Keeps pedestrians safe and slows down traffic. As stated before people just don't use the bridges once they are built unless you spend 4 times the cost of the bridge on extra civil works to make the bridge the only option.
One other point,and it covers many threads, is, Qatar is NOT full of idiot drivers, there are a few granted but if you really want to see a land full of idiots behind the wheel,spend a little time in Saudi,the roads here are heaven compared to there!