When you are driving in a known high-risk area for this crime (you can learn this by asking locals and by regularly reading the metro page of the newspaper or watching daily news), be particularly on guard for events around you, which could lead up to a car-jacking. Some signs are that you are being boxed in closely in traffic--especially at a stop sign. If you sense that such an event is happening, avoid it by defensive maneuvers with your automobile. The most drastic of such maneuvers might be to drive onto the sidewalk or other normally prohibited area, or even to crash into either car, front or back or side, in an effort to remove oneself from the situation. In such drastic events, just be pretty sure that you are correct.
Another tell-tale sign might be one or more people approaching your car whether in conjunction with or separate from being boxed in. People have an innate ability to detect such conditions, if they will open themselves up to it, and consider, ahead of time, that such events really can happen. Also use the color coded system discussed earlier in a post that used the national color codes for terror alerts for a personal system to assist you in not being caught off guard.
By far the best means of stopping a car-jacking, from which you ca not remove yourself quickly, is a handgun. A handgun on your hip, is not very accessible. There is a maneuver intended to trick the car-jacker by making it look as if you are merely unbuckling your seat-belt, while you are also accessing your holstered handgun--with with you will promptly shoot the assailant. This is not the time to be squeamish. Decide what you will do ahead of time.
I believe a better, more forward thinking use of your handgun, is to carry between the seats, accessible to you while driving. Or carry it in you lap, secured from flying forward with car movement, by placing it slightly under one leg. This is the least obvious and fastest place from which to access your handgun.
I often carry a hammerless lightweight 38 special. Most of my upper sports coats and other jackets have been altered to carry a this weapon. In such cases I could very quickly fire from within this pocket through my clothing without th risk of malfunction due to the hammer catching on my clothing. This is an advantage to such a hammerless revolver. But it does require you to remember to change it back and forth, as does the method of placing the handgun between the seats. It can easily be forgotten and left there. Not good.
I alternate the loads in my pistols to begin with a metal jacketed bullet or two followed by hollow-points or fragmented bullets. This technique is to have the ability to fire through a windshield initially if necessary. A hollow-point or fragmented self-defense round is apt to crush completely when it hits a closed window, without any stopping power at all. this must be considered.
the use of a handgun presupposes that you can and do legally carry one. In the event that you don't, several other items can be helpful as weapons to repel a car-jacker. One is to carry one of the following items readily available in the next seat or propped vertically between seats: a large mag-light, a heavy metal steering wheel locking device, or a short umbrella.
Savagely striking your attacker as you get out of the car when ordered to do so can have dramatic results. Even scratching in the eyes with keys, spraying pepper-spray when approached, or using a key-chain weapon called a cu-baton are also possible options. If trained to do so, a car-jacker, places himself in a vulnerable position for you to adopt a choke-hold on him. Even slightly built people can be trained to effectively render a person unconscious within seconds.
There are also car-door maneuvers that can help you evade a car-jacker. You can open the door on him hard and fast and/or close the door on his arm or body and inflict considerable deterrent injury. Again it comes down to your early plan and decision to viciously counter-attack in an effort to refuse becoming a victim. If you do so, your chances of survival sky-rocket. If you are taken hostage, and don't resist, your odds for survival plummet.
One last consideration is a special case of car-jacking or robbery. Your color code should be on orange or red anytime you are outside your car preparing to reenter. The most used moment for attack in this condition is while you are refueling your car. The criminal can simply come up to you with areal or pretended weapon and demand your wallet and your keys. If you are vigilant, no one should ever be able to get this close without your protest.
If you scream or speak gruffly to anyone entering your protective space, or zone of comfort, you will be wise. If you are armed or have a can or other object in your hand, use it menacingly. If it is a mistake, it is the advancers mistake, not yours. No one should ever invade your comfort zone unchallenged.
Links: The Wright Place