Breakdowns happen to the best of us, even those who scrupulously adhere to their auto maintenance schedules. The best way to survive this sort of trauma is to stay calm; the best way to stay calm is to have a plan, and some basic knowledge of what caused the breakdown. And it also helps to carry a charged cell phone.

Now or Later
Breakdowns come in two categories: those that require us to stop immediately, usually because the vehicle is incapacitated and you have no choice. And those that present a narrow window of opportunity to quickly find a safe place to pull over. The former category may be signaled by an "idiot light." For instance, once the oil light comes on, your engine may be in serious trouble and should be shut down immediately.

With gauges that record temperature or alternator functioning, you have the luxury, or agony, of a more advanced disaster warning. A good rule of thumb with both temperature and alternator is to know what's normal for the specific vehicle and what's dangerously abnormal. For instance, pick-ups on flat highways with no load easily run below the 200-degree mark, but when running up steep grades with a heavy load, the temperature will rise steadily.

With the battery, or alternator, gauge, the needle may fluctuate in stop-and-go traffic or in the rain at night. In other words, when the electrical system has a full load. If you're cruising along in normal driving conditions with little load on the system and notice the needle is sinking, it's time to worry.

When a breakdown is imminent, signal (by hand, if necessary) and get completely out of the flow of traffic. If the nature of your breakdown is going to cause your vehicle to drive erratically, turn on your flashers to alert other drivers.

Once you're safely off the road, be sure your flashers are on. Raise your hood, even if the engine isn't the problem, since that's the universal sign for a breakdown. Also set out flares or warning triangles, if it is safe to do so, behind your vehicle. The safest place for you, especially on a busy freeway or at night on urban roadways, is not in your vehicle. Stay near—but never get between traffic and your disabled auto.

Here's where pre-planning comes in handy. Call for help. That may be in the form of a friend, an auto club or your trusted mechanic. Avoid dialing 911 unless there is immediate danger to you or passing motorists. Some state freeways have call boxes, but be cautious if you've broken down at night with no call box in immediate sight. Now, for specific breakdown scenarios:

Overheating
An obvious of overheating is either the temperature warning light or a temperature gauge needle that's into the red area. Steam billowing out from underneath the hood is a pretty good clue as well. Pull over as soon as you safely can and shut off the motor. If you see or smell steam, raise the hood and check for a broken hose, leaking radiator or engine core plug. Check the engine drivebelt that operates the water pump. If you identify a major leak or broken drivebelt, don't try to drive the car. Get help.

Do not ever remove the radiator cap while the engine is hot or even warm. When you've checked for possible leaks or broken belts and everything is intact, wait until the top radiator hose is no longer hot to the touch, about 30 minutes, before you check the radiator. When the engine has cooled, you can add water to the cooling system through the coolant recovery, or overflow, reservoir under the hood. You may not have to deal with the radiator at all.

After you've been on the side of the road for half an hour and added water to the reservoir, you still may not be able to figure out why you've overheated. It's probably safe to restart your engine and proceed to a facility to get the vehicle checked out. Be prepared to pull over and let the engine cool if it continues to overheat.

Electrical Problems
With an electrical problem, the charging system warning light will come on, or you've noticed your gauge is hovering low. Pull off the road safely, but don't turn off your engine. The process of starting an engine requires a significant amount of juice, which now may not be available. The first thing to check under the hood is the fan belt—the one that drives both the alternator and the water pump. If this belt is broken, go ahead and turn off the engine. You're not going anywhere because if your vehicle isn't overheating, it soon will.

If this belt is intact, then turn off everything but your engine, such as your air conditioner or heater and radio. You may not have the option of turning off your headlights or windshield wipers, but if you can safely drive without them, do. Your alternator or generator is dead, but your engine can drive off of a fully charged battery for about an hour (assuming that it has a full charge).

Brake System
When the red brake warning light comes on, you may still have some braking power (let's hope so!), but it is probably reduced and you will require much greater braking distance. Get off the highway, using your emergency brake if necessary. Ease the parking/emergency brake lever on, keeping your finger on the release button. When you feel the brakes start to lock up, release the button and start again.

If you're in heavy traffic, turn on your flashers and/or use your horn to alert surrounding motorists that you've got a problem. There are some situations where you can get to help with a failing brake system. For instance, if the brake caliper is broken and you've leaked brake fluid, a few quick pumps of the brake pedal can get the pressure back up. But if at all possible, just stop the car and call for help.

Obviously, we haven't covered all the possible causes of breakdowns, just a few of the most common. The best test for whether you should tough it out and drive to help, or give up and pull off the road, is the degree of danger that your vehicle's malfunction exposes you and other motorists to. It's always better to err on the side of safety.