While I don't have any safety statistic for Vanagon, I do know that they are
very safe. 
Here is my own experience and it happened only a few days ago on New Years
Day.
I was driving on Brooklyn-Queens Expressway (aka I-278) in New York City on
New Years Day. The car in front of me suddenly slow down so I had to slow
down also. When I was slowing down I turned on the hazard light. Two seconds
later, I heard a loud skidding sound and a Jeep Grand Cherockee slammed into
my rear. In me horror, I saw that Jeep caught fire and then exploded... right
behind my Vanagon. Luckily, the two passenger of that Jeep was able to get
out in time. And the Vanagon was able to restart
and drove away from that fireball.

Of cause that Jeep was totalled, but the Vanagon could still move on its own
power. Yes,  the body suffered damages but its is repairable (according to
the body shop).

I and my wife also injured but not too seriously. We were taken to hosipital
and were discharged on the same day.

About 1.5 ft of the rear of the Vanagon was folded in, but since the damages
was mostly on and above the bumper, the engine compartment was mainly intact.

I would say this brick is pretty strong. I was driving a Fiat X1/9
before...if I were in that car....well.

Now, anybody has a 87 or newer Vanagon to part out. I am interested to know.

Best Regard