I've wondered about this for years. It's become quite popular to film car crashes from inside the vehicle that suffers the worst damage. These scenes are usually shot from inside the "target" vehicle, looking out a side window as the oncoming "t-bone" impact happens. It seems especially popular in espionage/suspense/thriller types of films/shows.
Here is an example from the movie Adaptation (not at all one of the best FX examples as it's quite old, but it's the only one I could precisely recall off the top of my head)
Here is another (pretty poorly done, IMO) example that cuts just before any crash is actually seen, but if they had gone all the way past the point of impact, this is the kind of scene I'm talking about:
How exactly do they do this? I'm assuming it's a combination of practical and CGI, since it's usually done in such a way as to definitely be able to clearly see the actor's face so as to lend realism to the shot, yet obviously would be way too dangerous to the actor to actually execute. But some of these done more recently look so shockingly real... how do they pull it off?