Back to techie stuff about barriers ...
Robert Kubica's co-driver, Jakub Gerb has said:
We knew the surface was slippery because of the humidity and we were ready. After skidding, the car leaned against the guard rail and pushed it outwards. Then it crashed against the following guard rail.
That's the scenario I described earlier, the barrier directs the car into another obstacle. The severity of the accident is due to the gaps in the barrier. That probably wouldn't have been a problem for a conventional road car traveling at lower speed.
The irony is that it would have been safer for him if the barrier had been completely missing, the roll structure is designed for the sort of drop we can see in the pictures.
If you look at the in-car video there are a lot of hazards along that route. Sections without any barrier, and barriers that stop and start too soon.
You can see the car behind Kubica parked next to a lamp post. I'm sure a the roll cage would do nothing to protect a rally car if it hit that sideways on.
There are probably some measures that could be taken to improve safety such as closing gaps in barriers, and adding protection to posts, but they would be disproportionately expensive. I'm not sure how one could strengthen the car against a point load either, unless you turn it into a tank.
Then you think of the rescue equipment. I suppose they could have had more cutting equipment available to reduce delays. However, access will always be difficult, most rallies aren't held in the sort of terrain suitable for helicopter landings.
Do we really want to impose safety restrictions that put rallying out of reach of the enthusiast driver, and only allowed on expensively prepared routes?