I'm planning to travel by bus between Mendoza, Argentina and Santiago, Chile. I don't have a head for heights, hence my question:
Are there any terrible precipitous drop-offs on the edge of the road whilst crossing the Andes by bus?
This is one of my favourite bus trips in the world, having done Mendoza->Santiago twice and Santiago->Mendoza once. Please, please, travel it during the day, for two reasons:
1) I've done this once at night. At the top of the Andes is the border crossing. There's snow a good portion of the year on the hills around you. It's FREEZING in the middle of the night standing in this big warehouse waiting for your turn to get a stamp.
2) It's spectacular. On the way up you can actually see the Inca Bridge from the bus - keep a look out for road signs. Just before the Argentinian border, if you know where to look on the right side of the bus, you have a 20-30 second window where you can see Aconcagua. The mountains are fantastic, and the roads are actually really good.
Now, in terms of drop offs. The final time I did this trip was with a friend who does NOT have a good head for heights. Heights freak him out something chronic. He was fine the entire bus ride. The roads are good, they have tunnels at key points rather than make a risky road or risk avalanche.
Checking my blog, I didn't provide much description, but...
Now, there is ONE key point that might freak you out a little bit. I actually mention it in the first post above, as:
This is through the pass called Paso Internacional Los Libertadores and is a series of 27 switchbacks on the Chilean side. It becomes almost monotonous going up, but the view going towards Chile (down) is spectacular. But even my friend with a fear for heights marvelled at it (and he did the trip twice).
But the road has lots of traffic, the buses are very good quality, and the trip takes about 8 hours. It's a fantastic way to spend a day.
(EDIT) If you really want to see what it looks like, there's a video of some of the switchbacks showing the drops, but also the inside of the bus and how slowly the bus goes to make sure it's safe. You'll be fine :)
The photos and descriptions on this website might give an idea of how it's like: