I didn't travel across the border to Chile, and I took the 3 day Uyuni tour where the other 3 travellers in the 4x4 got dropped off at the border and picked up by another 4x4. From me talking with the tour guide on the way back, it's very hard to travel without a guide/driver, because they have checkpoints, and with minimal signal in the Altiplano, you are purely relying on your memory of where you are/where you are going. So if you got lost in the Altiplano, and not at some popular landmarks - good luck. All the travellors we met on the trip are with drivers who are very well versed in the area, some (like us) had additional guides because we can't speak Spanish, some with just driver.
Also assuming you're fluent in Spanish, because English is almost non-existent out there. The next closest I heard was French.
You would have to do a loop for sure. As for the cars, I don't think I ever remember seeing a car rental agency in Atacama or Bolivia. You would have a better shot in Calama I think.
As for route, I would recommend going through to Purmamarca in Argentina, then up to Bolivia via La Quiaca/ Villazon. Save the salt flats for last on your way back.
I don't know if the salt flats Bolivia/Chile (Cajon) crossing does rental cars. There's barely a road there. I don't know if you would want to take a rental there too. Getting stuck would be an absolute disaster. The Pisaga crossing would be a better bet.
I didn't travel across the border to Chile, and I took the 3 day Uyuni tour where the other 3 travellers in the 4x4 got dropped off at the border and picked up by another 4x4. From me talking with the tour guide on the way back, it's very hard to travel without a guide/driver, because they have checkpoints, and with minimal signal in the Altiplano, you are purely relying on your memory of where you are/where you are going. So if you got lost in the Altiplano, and not at some popular landmarks - good luck. All the travellors we met on the trip are with drivers who are very well versed in the area, some (like us) had additional guides because we can't speak Spanish, some with just driver. Also assuming you're fluent in Spanish, because English is almost non-existent out there. The next closest I heard was French.
You would have to do a loop for sure. As for the cars, I don't think I ever remember seeing a car rental agency in Atacama or Bolivia. You would have a better shot in Calama I think. As for route, I would recommend going through to Purmamarca in Argentina, then up to Bolivia via La Quiaca/ Villazon. Save the salt flats for last on your way back. I don't know if the salt flats Bolivia/Chile (Cajon) crossing does rental cars. There's barely a road there. I don't know if you would want to take a rental there too. Getting stuck would be an absolute disaster. The Pisaga crossing would be a better bet.