They had to encase the whole bridge above to stop it
well it is wise to, as it mostly happens at night when it's quieter,it's mostly Durban Joburgh. Just did a quick search
https://www.enca.com/south-africa/tips-to-avoid-off-bridge-rock-throwing-scourge
https://southcoastsun.co.za/116733/tips-avoid-survive-rock-throwing-incidents/
Still don't get me wrong it is a great place to go to ,but you just need to keep your wits about you and have a awareness space around you