Choosing a safe and sustainable car

Features that affect the environment

Air-conditioning

You should be able to adjust the temperature and ventilation to suit weather conditions. Air conditioning helps prevent fatigue by keeping you comfortable and also demists the windows in wet or humid weather. Air conditioning provides real safety benefits; however, using it will increase fuel consumption. At speeds of less than 80 km/h it may be more fuel efficient to open car windows instead.

Exhausts

A good exhaust system is important not only for your safety but also for the environment, as it will reduce emission of greenhouse gases and other pollutants. It will also reduce another environmental effect, noise. For the good of others, and the environment, make sure your exhaust doesn’t pollute the air with emissions, smoke or excessive noise.

- Leaky exhausts

With a good exhaust system the vehicle is sound, with no leakage of gases into the passenger compartment. For your own safety, check your exhaust has no leaks. An exhaust leak can be very dangerous. If the exhaust finds its way inside the vehicle, carbon monoxide poisoning can result. The smell of burning oil can mean a worn-out engine. If you can smell petrol fumes while you are driving, you may have an exhaust leak. This can be very dangerous, as carbon monoxide leaks can poison you and your passengers and you could pass out behind the wheel.

- Emission of pollutants and smoke

With a good exhaust system the vehicle burns the fuel efficiently, makes effective use of whatever catalysts, filters etc were installed at manufacture, and emits fewer pollutant gases that affect air quality. Keep the engine tuned and maintained. Checks for smoky vehicles are now part of the Warrant of Fitness. Some causes can be easily fixed, eg, by changing the air filter. Sometimes the vehicle may require a simple tune-up. In other cases, the vehicle’s engine condition may be more serious and require extensive repairs. You should consult a mechanic with experience in this area to ensure the most effective repair for your vehicle.

- Emission of noise

With a good exhaust system and effective silencer the vehicle does not make excessive noise when operated. An objective noise test has been developed to ensure vehicles are not excessively noisy. An objective noise test uses scientific procedures to measure noise levels. The equipment measures the vehicle's exhaust noise levels against a pre-determined standard.

Tyres

Tyres are one of the most important safety features. Whenever a vehicle accelerates, corners or brakes, it puts force on the tyres. Good tyres grip the road, which is crucial in helping avoid crashes.

Choosing the right tyre depends on the type of vehicle and how it will be used. Tyres that suit a car used for city driving could be unsuitable for one carrying heavy loads or used off-road. The tyres fitted by the manufacturer are suitable for everyday use on most vehicles, but it’s a good idea to discuss tyre choice with the dealer or a tyre specialist.

Tyre safety & maintenance

• Choose tyres with an approved standards mark. It is illegal to use or sell tyres that do not comply with an approved standard.
• Check the tyre pressure often. This will optimise performance, load-bearing and wear, and also cut down on fuel consumption – driving on poorly inflated tyres uses more fuel.
• Having tyres of different construction or size fitted to the same axle is dangerous and illegal.
• Ideally, all tyres on a vehicle should be of the same construction, as mixing tyre types affects driving control. Tyres should be replaced in sets of four (or at least in pairs on the same axle) to maintain consistent handling. At the very least, the same type of tyre should be fitted to the same axle (front or rear).
• Every tyre has a maximum speed rating. A tyre with a high speed rating will generally grip and perform better at higher speeds than one with a low speed rating.
• A tyre has a load index that indicates its maximum carrying capacity. Ensure vehicles carrying heavy loads have tyres capable of safely bearing the weight.
• Car manufacturers recommend that replacement tyres be the same type as those originally fitted, to maintain all-round driving performance.
• If the size of a replacement tyre differs from that of the original tyre, ensure the new size is compatible with the wheel rim size and that adequate clearance exists in all conditions (including when snow chains may need to be fitted).

Choosing tyres

No tyre is perfect for all driving conditions. When choosing tyres, you should select ones appropriate for your vehicle and the kind of driving you will be doing.

Long-life tyres made of hard compounds usually last longer than softer tyres, but may not grip as well, particularly in the wet. A tyre with a big 'footprint' (the surface area in contact with the road) will provide good grip in dry conditions, but may not grip as well on wet roads.

Ideally, tyres should be renewed in sets of four. If this is not possible, tyres should at least be replaced in pairs on the same axle. Most tyre manufacturers recommend placing the tyres with the best grip and cornering power (new tyres) at the rear, whether the car is front or rear wheel drive. Fitting new tyres to the front can result in oversteer and loss of control.

Tyre size and construction

Make sure your tyres are the correct size and that they are fitted to the correct rim size. If the size of a replacement tyre differs from the original, make sure that the new size is compatible with the rim size and that there is adequate clearance for all conditions, including when snow chains may need to be fitted.

Always check with a tyre specialist before changing an original rim or tyre fitted by the vehicle manufacturer. Fitting tyres with a different diameter to the originals will affect the accuracy of the speedometer and odometer. If you fit wider wheels and tyres, an increase in wheel offset beyond 25 mm overall, will require the vehicle to be certified by a Low Volume Certifier.

Speed ratings and load capacities

Every tyre has a maximum speed rating and a load index that indicates its maximum carrying capacity. A tyre with a high speed rating will probably perform better at high speeds than one with a low speed rating. If you carry heavy loads in your vehicle, make sure it is fitted with tyres capable of safely bearing the weight. Tyres are marked with symbols that indicate their maximum speed ratings and load capacities.

Balance

No matter how well a tyre is made, its life and performance depend largely on how it is treated. Safe driving, regular inspections and rotating tyres - moving tyres around the car to help keep wear patterns even - are all essential components of good tyre care.

Correctly balanced wheels will ensure smooth and vibration-free running and improve tread life, as well as extending the life of the vehicle's suspension and steering components.

Tyre inflation

Check the inflation of all tyres - including the spare - every two weeks, while tyres are cold. Even a short trip to the garage will warm up tyres and raise the pressure. (Remember, space-saver spare tyres must be inflated to a much higher pressure than normal tyres.)

Correct tyre pressure is vital for balanced braking, maximum grip and long tyre life. Under-inflated tyres will increase fuel consumption and affect the safe handling of the car, while over-inflation can mean an uncomfortable ride and reduced grip. Both under and over-inflation will cause your tyres to wear out sooner.

Legally, tyres are required to be maintained at the pressure recommended by the vehicle manufacturer. All modern vehicles have a tyre information placard in a conspicuous place, showing the correct inflation levels for normal driving, as well as for higher speeds and maximum loads.

Tread wear

Good tyre tread is necessary to maintain road grip, especially in wet weather. Legally, for tyres fitted to most types of vehicles, the tyres must have a tread pattern of at least 1.5 mm deep in all the principal grooves of the tyre (excluding any tie-bar or tread depth indicator strip) and around the entire circumference of the tyre. The principal grooves are the ones containing moulded tread depth indicators.

Tread wear isn't the only factor that reduces grip in older tyres. As most tyres age, the rubber hardens, further reducing wet-weather performance.

Directional tyres

Some high performance tyres have directional treads. These tyres are designed to rotate in one direction only, to provide handling and performance benefits.

If these tyres are fitted the wrong way around, in the wet the tread pattern will effectively dam up water and reduce grip. When fitted facing the wrong way, directional tyres can also cause vehicles travelling at high speed to become unstable.

Tyres with asymetrical treads have tread patterns which vary across the width of the tyre and must be fitted to the vehicle as indicated on the tyre. If directional tyres are moved from one side of a vehicle to the other, the tyres must be removed from the rims and turned around to face in the proper direction.

Tyre repairs

Manufacturers have firm guidelines on which parts of a tyre can be repaired. Always check these before carrying out repairs.
Currently the law requires repairs to return tyres to 'within safe tolerance' of their state when manufactured. It’s likely that tyre repairs will be required to meet approved standards in the near future.

Many garages sell 'string repair' kits or sealants as a quick-fix solution for tyre punctures. String repair kits use a fibre cord or rubberised string-type plug pushed through from the outside of the tyre to seal a puncture. Tyre makers warn that these repairs are only good for 160 km of driving at a maximum speed of 80 km/h. If a proper repair isn't carried out, the object that caused the puncture can remain in the tread scraping out the sidewall, or water can get into the tyre's casing and deteriorate the reinforcing material. Either of these can lead to a tyre rupture or blow out.

Similar to string repairs, sealants are injected into tyres. Preventative sealants can cover over a puncture hole, but the seal will be on the inside of the tyre and the hole on the outside may allow moisture to enter the casing. This can deteriorate the reinforcing material and lead to a rupture or blow out. If a sealant is applied through the tyre's valve it can also unbalance the tyre and wheel.

A string repair kit or sealant should only be used as a temporary measure until the tyre can be removed from the wheel and repaired. Vehicles with a sealant-repaired tyre should only be driven slowly and for short distances.

Some sealants are designed to be used in new, unpunctured tyres to limit the very slow loss of air pressure that usually occurs. These sealants are not intended for use as 'get-you-home' puncture repairs, but may be effective at reducing air loss when a sharp object punctures the tyre.

Space-saver tyres

Many modern cars are equipped with temporary-use or space-saver spare tyres which are smaller and lighter than standard spares. These tyres are usually about the width of a motorcycle tyre. Space-saver tyres normally need to be inflated to a higher pressure. Make sure yours is inflated properly.

Space-saver tyres should be used only in an emergency - they are not designed to be used over long distances. Space-saver tyres have a speed restriction of 80 km/h. Your vehicle's handling may also be different when a space-saver is fitted. Drive carefully and never fit more than one space-saver tyre to a vehicle.

As long as you keep to these guidelines and your space-saver tyre is in good condition, it is safe to drive on.