While it is possible to just mount your belts, thread them through your racing seats, and go hit the road, that method leaves far too much risk on the table. Proper shoulder harness belt angles should be maintained through the use of support bars. Harness bars, sold by vendors like Sparco USA, I/O Port Racing Supplies and M1 Development, are not designed to significantly add any sort of chassis stiffness. Rather, they are primarily in place to ensure proper harness mounting angles. Mounted directly behind the driver's shoulder level, harness bars are a solid method to ensure proper harness mounting at all times without having to install a roll cage. The only downside is due to the solid construction and placement within the cabin, passengers should not be riding in the backseat of any harness bar-equipped vehicle because of the danger of contacting face to harness bar. That's right, your Civic just became a two-seater.
If you can't hold rear seat passengers anyway, why not just move up to a full 56-point roll cage, right? If only it was that easy. A roll cage with a rear cross bar has the same capability as a harness bar to properly position the angle of shoulder harness belts, but there are other issues on hand that draw the distinction between using a roll cage, a roll bar, or a harness bar. Obviously, the biggest difference between the three lies in roll over protection. A harness bar is not designed to support the roof in any way during a roll over; its only function is to ensure proper harness mounting. Resting one step up from a harness bar is the roll bar, available from such vendors as Autopower and Kirk Racing. Offering rollover protection, but lacking the forward hoops and door bars that a full cage provides, a rollbar is the usually the choice for street-driven track monsters.
Required by many road racing organizations and mandatory in the NHRA drag racing ranks depending on e.t. or trap speed, roll cages are not for the average street car. A full cage will provide greater protection from deformation of the cockpit during crashes, but there are inherent dangers from installing a full cage in a streetcar. Roll cages are supposed to be made from metal tubing, and in the event of an accident, if you hit your head on roll cage tubing, it's not going to be a pretty sight, especially for the coroner. By now, ideas are forming in your head and you think, "What if I cover my cage tubing with heater insulation? It looks like roll cage padding." Not so quick smart guy. Even genuine roll cage padding is designed only to absorb the impact of a helmeted skull, not your bare face, it won't make cage tubes soft enough to safely hit in an accident.
Take a look into your average World Challenge racecar, there's a full precision bent roll cage, FIA approved seating, properly mounted safety harnesses, a racing steering wheel, fire extinguisher system, nomex racing gear, and a quality helmet for the driver. Every area of safety equipment is designed to properly function together as one, and only by properly thinking ahead and balancing what you install will you stay safe. It may seem like in today's frantically dangerous world, the only way to be 100 percent safe is to put on your racing suit and helmet, strap into your caged, racing seat-equipped Corolla and go pick up some drinks from the supermarket. While that method is admittedly the safest way to go about commuting in our increasingly Mad Max-like world, it doesn't have to be that hard. A good seat and a properly mounted harness is an easy install with the right parts, and the results can be instantly felt everywhere you drive. Properly equipping your ride for grip and safety isn't a difficult thing at all, you just need to keep your head on straight. And that, my friends, is something done a whole lot easier if you keep yourself in one piece.