The Braking System
The principle behind the braking system of a vehicle is to convert kinetic energy (motion) into heat energy generated by the friction produced when the brakes are applied. As the brake pedal is pressed down the brake linings rub against the disc or drum creating friction proportional to the pressure applied at the pedal. This friction changes the kinetic energy into heat energy and when all the kinetic has been converted into heat the vehicle has come to a stop. The following factors may result in a brake systems failure and a resultant traffic accident:

1. Excessive wear of the disc brake pads and/or drum brake shoes. Note, most cars manufactured today have disc brakes on all four wheels rather than a disc braked front and drum braked rear.
2. Wear of the moving parts of the master cylinder, especially the seals, which may allow fluid to leak resulting in decreasing brake efficiency with the possibility of a complete brake system failure.
3. In a drum brake the wheel cylinder is a critical component, as any fluid leak will contaminate the linings of the brake resulting in reduced friction, and therefore stopping power, on that wheel, as well as damage to new brake shoes, or partial system failure. A sticking wheel cylinder may cause brake drag and/or imbalance, excessive pedal effort and reduced braking efficiency.
4. Faulty disc brakes can cause excessive pedal travel, a pedal that requires pumping or a pedal that needs "fighting", vibration under braking or brake failure.
5. A low level of brake fluid in the reservoir.
6. Rupture of the brake hoses or brake pipes.

Tyres
A tyre, apart from its own function of rolling on the road, also affects the general performance of the car. Having a lower pressure than prescribed in the manufacturer's handbook will affect stability during driving and can make the steering heavy during manoeuvring. It will also cause higher fuel consumption. Having a higher pressure than recommended results in faster wear of the tyre's tread, giving a harsh and bumpy ride, increased risk of skidding, as well as damage to the suspension system. The following factors can affect the normal operation of your car and could result in a traffic accident:

1. Incorrect and/or uneven tyre pressures;
2. Loose wheel nuts;
3. Depth of tread below the legal minimum, or that recommended by the tyre's manufacturer if greater;
4. Visible and hidden damage;
5. Wheels/tyres that have become out of balance;
6. Cross ply and radial ply tyres on the same axle;
7. Cracked or damaged sidewalls of the tyre; and
8. Defective and/or non-standard wheel rims.

The Steering System
The main function of the steering is to provide directional control of the vehicle. Generally, there are three fundamentally different system designs that are commonly used: rack and pinion, steering box and a hydraulically actuated system (not power steering - that is an aid to lessen the effort required of the two previous systems). In passenger cars the most common system is the rack and pinion. The following defects can lead to serious consequences is not rectified immediately:

1. Broken/damaged track control arm;
2. Excessive "play" in the steering;
3. Loose ball joints;
4. Loose or broken steering column;
5.  Broken and/or damaged components in a steering box
6. Damaged or leaking power steering hydraulic pump and system; and
7. Low fluid level in the power steering reservoir.

Lighting
Defective lights may sometimes not have an immediate, or apparent, effect on safe driving but rather be a latent, or hidden, problem. Driving at night time without headlights on is hazardous as there is not only a lack of good vision for the driver but also there is the problem that other road users may not be able to see you. Contributory factors include the following:

1. Defective headlamps and brake lights.
2. Defective auxiliary lights such as indicators, reversing lights, side lights and fog lamps.

Bodywork
The main function of a car's bodywork is to provide a structurally sound compartment for the driver and passengers, and it is designed to progressively absorb impact forces during a collision, as well as be a good dynamic platform for the suspension and steering systems. Well maintained bodywork plays a very important role in driver and passenger safety, especially in collisions with other vehicles or immovable objects. Buckled or misaligned bodywork is a danger to drivers and their passengers - as well as other road users and pedestrians, especially when driving around corners, and the following factors are a major cause for concern:

1. Bumper damage - as the bumper is the first component of impact absorption in a vehicle.
2. Heavy corrosion of the chassis/floor pan as well as loose parts.
3. Distortion of the bodywork, possibly due to previous impact damage.

The Suspension System
The suspension system has two primary functions: to keep the car's wheels in firm contact with the road and to provide a comfortable ride for the car's occupants. A lot of the suspension's work is done by the springs. Under normal conditions the springs support the weight of the vehicle evenly by compressing and rebounding with every up and down movement. This up and down movement, however, needs to be damped down otherwise the movement continues at a decreasing rate until it finally stops - very uncomfortable for the passengers! This undesirable effect is reduced to a minimum by the car's shock absorbers. When a shock absorber needs replacing they must be replaced in axle pairs, excessive rebound indicates a defective shock absorber which should be checked at a reputable garage. Factors that can contribute to poor performance include:

1. Incorrect linkage adjustment.
2. Loose or worn mounting bolts.
3. Weakening of the springs and shock absorbers due to age/use.

Visibility (Glass, Windscreen Wipers, Rear View Mirrors)
The windscreen wiper is there to help clean the screen and to provide the driver with a clear view of the road ahead during rain. Wiper blades, being rubber, are subject to deterioration due to UV radiation in sunlight. Once they have lost their edge they can no longer function as designed. In extremely cold weather the wiper blades may freeze onto the screen and using the wipers can damage the wiper motor. Likewise, in extreme weather conditions, or after the car has been parked in the sun for extended periods, the rubber can bond to the screen. Defective wiper blades will not clean the screen properly and will, therefore, not provide good visibility for the driver. A cracked or damaged windscreen will also impair the driver's visibility as well as providing the driver with possible distractions. It also has the potential to shatter completely, due to vibration, thus leaving the driver with little, or no, visibility. Rear view mirrors are also vital components which are often neglected. A rear view mirror should provide a full view of the traffic conditions behind the vehicle so that the driver can take any necessary actions required to avoid an accident. The following factors can impair a driver's vision which could give rise to a traffic accident:

1. Deterioration of the rubber of the wiper blade.
2. Damage to the wiper motor.
3. Damage to the screen itself, e.g. cracks.
4. Low liquid level in the washer bottle.