Sorry to hear the bad news, but "big and heavy" is rarely safe, principally. Look at modern crash test (NHTSA and Euro NCAP). Cars that you think would do well in a crash, do not and vice versa. One of the safest cars on the road is actually a Mercedes SMART car. Due to the short overhangs front and rear, there is no space to build a crumple zone. A UK television show called FIFTH Gear, crashed a SMART into a concrete barrier at over 40 MPH and could still open the doors easily. People look at the car and say, "oh it's small, that thing is a death trap." Race cars are small and light and they fair quite well in a crash (see below)
Mercedes builds what amounts to an internal roll cage, into the car, during manufacturing. It is not necessarily done with tubing, as you would add one into a race car or Jeep, but it is there. Have you ever seen a 57 Chevy crashed or an old Thunderbird? Big heavy car with a long front end, right? Force equals Mass times Acceleration (or Deceleration). A big heavy "anything" has more mass, more momentum and is thus harder to stop, needs more crumple zones to dissipate the energy of a crash, etc.
Look at modern race cars like WRC or Formula 1. They are basically jungle gyms (WRC) with Aramid or carbon body panels that tear apart and fly off, even in a minor crash. This dissipates a huge amount of energy. A modern F1 car can take MASSIVE impacts at 100 - 150 MPH, without so much as a scrape or scratch to the driver. Try that in your Mustang or Dodge pickup truck and you will be dead. The F1 cars fly apart, thereby dissipating energy as it comes apart in the crash, saving the driver and the chassis of the car. Wings, suspension and wheels can be replaced.
Hopefully, this technology will work it's way into modern cars, along with composites, like carbon reinforced plastic body panels instead of steel ones, thereby making all automobiles safer in a crash.