If you have a look at the corners of the oval circuits in the US you'll see there are two "walls" the original outside wall and then a separate tubular wall about a few feet apart. Between this is a very dense foam, so in the event of a car hitting the wall, it will move to try and dissipate the energy. It's a very simple idea but it works very well. The damaged pieces of foam can then be removed and replaced as needed.
Not so much in Indycar but certainly in NASCAR it's saved a lot of people from bad injuries (simply because of the weight of the car, inertia, etc.) They use SAFER barriers on the inside walls as well. I can't remember which race it was but someone went into one inside wall at about 160-180mph. The accident was so violent if that had still been a concrete wall still he would have been badly beaten up, as it was he managed to climb out the car unaided.
Why not make them softer? Well you then have the issue of bouncing. At the moment the SAFER wall contains the accident, if you made it softer or rubbery the car will either bounce away or into oncoming traffic.
Make no mistake oval racing is still very dangerous but with SAFER barriers and HANS it's a lot safer than it was a few years ago.
I wonder though if with Bourdais's accident they might try and extend the side pods forward or maybe add on an additional crash structure, we'll see.
