$1:
Boat.
The highway was opened in 1958 (or maybe a year earlier). The train tracks run pretty much alongside the road, so if one is out, they both are. There is still a port there, and an airport, so if someone/thing really needs to get in or out, there are ways, but for most people, it's just the road.
This is exactly why we've been saying for YEARS that the road needs to be upgraded.
Actually... more like decades.
It's not about latte's at Timmy's though. It's about milk.
There isnt an engineer in the world that would guarantee they could make that safe.
The money it would take to rockbolt that wall would be insane and it will fail if mother nature wants it to anyways.
I have some pics of failures that werent supposed to happen,way bigger then that one and preventive measures were taken such as rock bolting and installing extensiometers.