Traffic signsChile

Learn traffic rules with clear explanations and visual examples in our illustrated book, designed to make studying simple and engaging.


151. Diesel engine

A diesel engine is an internal-combustion engine that normally ignites fuel through the heat created by highly compressed air rather than by using spark plugs. For this reason, it is also known as a compression-ignition engine.

Diesel engines are commonly used in passenger cars, trucks, buses and machinery because they can provide strong low-speed torque and efficient fuel use. Modern diesel engines use emissions-control systems such as particulate filters and selective catalytic reduction to reduce harmful exhaust emissions.

Diesel engine
YaMZ-534 diesel engine for Tigr and Volk vehicles.
Wikimedia.org • Vitaly V. Kuzmin • CC BY-SA
How does a diesel engine work?

A diesel engine compresses air inside the cylinder until it becomes very hot. Diesel fuel is then injected into the compressed air and ignites because of the high temperature.

What is the difference between a diesel and petrol engine?

A diesel engine normally uses compression ignition, while a petrol engine normally uses spark plugs to ignite an air-fuel mixture. The two engine types also differ in fuel, combustion characteristics and emissions-control systems.

What emissions can a diesel engine produce?

Diesel engines can produce pollutants including nitrogen oxides and particulate matter or soot. Modern vehicles use systems such as diesel particulate filters and other emissions-control technologies to reduce these pollutants.

152. Electric motor

An electric motor is a machine that converts electrical energy into mechanical power. In an electric or hybrid vehicle, one or more electric motors can provide the torque needed to drive the wheels.

Electric motors can deliver torque from very low speeds and operate without the combustion process used by petrol or diesel engines. During regenerative braking, some electric motors can also operate as generators and convert part of the vehicle's motion back into electrical energy.

Electric motor
Tesla Model S platform chassis showing the electric drivetrain. (San Jose, California, United States)
Wikimedia.org • Oleg Alexandrov • CC BY-SA
What does an electric motor do in a vehicle?

An electric motor converts electrical energy into mechanical power that can propel the vehicle. Depending on the drivetrain, one or more motors may drive the wheels.

Do hybrid vehicles have electric motors?

Yes. Hybrid electric vehicles combine at least one electric propulsion motor with another propulsion-energy source, normally an internal-combustion engine.

Can an electric motor generate electricity?

Yes. In vehicles equipped with regenerative braking, the traction motor can operate as a generator while the vehicle slows down, converting part of its kinetic energy into electrical energy that can be stored in the traction battery.

153. Timing belt

A timing belt is a toothed belt in an internal-combustion engine that synchronises the rotation of the crankshaft and camshaft so that the engine's valves open and close at the correct time relative to piston movement.

The timing belt is a wear component and must be replaced according to the vehicle manufacturer's maintenance schedule. If it becomes excessively worn or breaks, the engine can stop suddenly and, in many engine designs, serious internal engine damage can occur.

Timing belt
Opel 1.0 ECOTEC direct-injection turbo engine displayed at the 2014 Paris Motor Show. (Paris, France)
Wikimedia.org • Thesupermat • CC BY-SA
What does a timing belt do?

The timing belt synchronises the crankshaft and camshaft so that the pistons and valves move in the correct sequence while the engine is operating.

When should a timing belt be replaced?

The replacement interval depends on the vehicle and engine. Drivers should follow the manufacturer's specified mileage and age interval rather than waiting for obvious symptoms of wear.

What happens if a timing belt breaks?

The engine will stop operating and, depending on the engine design, the pistons and valves can collide and cause severe internal engine damage.

154. Glow plug

A glow plug is an electrical heating element used in diesel engines to help ignite the fuel during cold starting. It heats the combustion chamber so that the compressed air reaches conditions suitable for reliable combustion.

Modern glow plugs can continue operating briefly after the engine starts to improve combustion, reduce cold-start emissions and help the engine run smoothly while warming up.

Glow plug
Diesel preheating and glow-plug dashboard indicator symbol.
Wikimedia.org • Chris828 • CC0
What does a glow plug do?

A glow plug heats the combustion chamber of a diesel engine before and during cold starting so that the injected diesel fuel can ignite more reliably.

Do diesel engines use glow plugs instead of spark plugs?

Diesel engines normally ignite fuel through compression rather than an electrical spark. Glow plugs therefore assist cold combustion but do not continuously ignite the fuel in the same way that spark plugs do in a petrol engine.

What are signs of faulty glow plugs?

Possible signs include difficult cold starting, rough running shortly after startup, increased cold-start smoke or a glow plug or engine warning light. Similar symptoms can have other causes, so proper diagnosis may be necessary.

155. Cylinder

A cylinder is a chamber inside a reciprocating internal-combustion engine in which a piston moves up and down. Air or an air-fuel mixture is compressed inside the cylinder, and combustion produces pressure that pushes the piston and helps generate mechanical power.

Most car engines have several cylinders arranged in configurations such as inline, V-shaped or horizontally opposed layouts. The combined swept volume of all cylinders is known as the engine displacement or cylinder capacity.

Cylinder
Engine block with visible cylinder bores.
Wikimedia.org • Nick johns • CC0
What happens inside an engine cylinder?

A piston moves inside the cylinder while the engine draws in air or an air-fuel mixture, compresses it and uses combustion to create pressure. This pressure acts on the piston and contributes to turning the crankshaft.

How many cylinders does a car engine have?

The number varies by engine design. Common passenger-car engines can have three, four, six or more cylinders, while some engines use different configurations according to their size and performance requirements.

What is cylinder capacity?

Cylinder capacity or engine displacement is the total swept volume of the engine's cylinders. It is commonly expressed in cubic centimetres (cm³) or litres.

156. Engine oil

Engine oil is a lubricant used inside an internal-combustion engine to reduce friction and wear between moving components. It also helps remove heat, keep internal surfaces clean and protect components against corrosion.

The oil level and condition should be checked according to the vehicle manufacturer's instructions. Only oil with the correct specification and viscosity should be used, and the oil and oil filter should be replaced at the recommended maintenance intervals.

Engine oil
Using a funnel to refill the engine oil in a car as part of an oil change.
Wikimedia.org • Dvortygirl • CC BY-SA
What does engine oil do?

Engine oil lubricates moving components, reduces friction and wear, helps carry away heat and keeps contaminants suspended so that they can be removed by the oil filter or during an oil change.

How do you check the engine oil level?

Depending on the vehicle, the level is checked with an oil dipstick or an electronic oil-level system. The vehicle manufacturer's instructions should be followed because the required procedure can vary between engines.

Can you use any engine oil?

No. Engine oils have different viscosity grades and technical specifications. Only oil meeting the requirements specified by the vehicle manufacturer should be used.

157. Coolant

Coolant is a fluid that circulates through a vehicle's cooling system to remove excess heat from the engine or other components. It usually contains water mixed with antifreeze and corrosion inhibitors so that the cooling system can operate safely across a wide range of temperatures.

The coolant level should be checked according to the vehicle manufacturer's instructions. The correct coolant specification must be used, and the cooling system should only be opened when it is safe to do so because hot coolant can be under pressure.

Coolant
Refilling coolant/antifreeze.
Wikimedia.org • Gasper12345 • CC BY-SA
What does engine coolant do?

Coolant absorbs heat from the engine and carries it to the radiator, where the heat can be released. It also helps protect the cooling system against freezing, corrosion and excessive temperatures.

Can you use any type of coolant?

No. Vehicles can require different coolant specifications and mixtures. Drivers should use coolant that meets the vehicle manufacturer's requirements and avoid mixing incompatible coolant types.

Should you open the coolant reservoir when the engine is hot?

No. A hot cooling system can be pressurised and opening it can release hot coolant or steam. Allow the system to cool and follow the vehicle manufacturer's instructions before opening the reservoir.

158. Maintenance

Maintenance is the regular inspection, servicing and repair of a vehicle to keep it safe, reliable and in good working condition. It includes tasks such as checking fluids, tyres, brakes, lights and other components and replacing worn parts when necessary.

Maintenance should follow the vehicle manufacturer's recommended service schedule. Regular maintenance can help prevent breakdowns, reduce wear, maintain safety systems and identify defects before they become more serious.

Maintenance
Vehicle technician working on a truck transmission at RAF Lakenheath.
Wikimedia.org • Nigel Sandridge • CC0
Why is regular vehicle maintenance important?

Regular maintenance helps keep safety-critical and mechanical systems working correctly, reduces the risk of breakdowns and can identify worn or damaged components before they cause larger problems.

What does routine vehicle maintenance include?

It can include checking and replacing engine oil and filters, inspecting tyres and brakes, checking fluid levels, lights, suspension and other components, and performing other work specified by the vehicle manufacturer.

How often should a vehicle be serviced?

Service intervals depend on the vehicle, engine, mileage, age and operating conditions. Drivers should follow the maintenance schedule provided by the vehicle manufacturer.

159. Spare tyre

A spare tyre is an additional tyre, usually already mounted on a wheel, carried in a vehicle so that a damaged or punctured road wheel can be temporarily replaced. Vehicles may carry a full-size spare wheel, a compact temporary spare or a tyre-repair kit instead.

A temporary spare wheel is normally intended only for emergency and short-term use. Drivers must follow the manufacturer's restrictions concerning speed, distance, tyre pressure and installation and should replace or repair the damaged normal tyre as soon as possible.

Spare tyre
Spare wheel of a Bentley Bentayga.
Wikimedia.org • Mike-fiesta • CC BY-SA
What is a spare tyre?

A spare tyre is an additional tyre, normally mounted on a wheel, that can temporarily replace a punctured or damaged road wheel.

Is a spare tyre the same as a spare wheel?

In everyday use the terms are often used interchangeably. Technically, a spare wheel usually consists of both the wheel rim and the tyre already fitted to it.

What is a space-saver spare wheel?

A space-saver is a smaller and lighter temporary spare designed to take up less storage space. It normally has stricter speed and distance limitations than a normal road wheel.

Can you drive normally on a temporary spare wheel?

No. Temporary spare wheels are intended for emergency use. Follow the maximum speed, distance and other restrictions specified by the vehicle or tyre manufacturer.

Do all cars have a spare tyre?

No. Many modern cars instead use a tyre-repair kit, run-flat tyres or roadside-assistance arrangements.

Can a tyre-repair kit replace a spare wheel?

For some punctures, yes. A repair kit may temporarily seal a small puncture, but it may not work for severe tyre damage, sidewall damage or a damaged wheel rim.

Should you check the pressure of a spare tyre?

Yes. A spare tyre can lose pressure while stored for long periods. Check it periodically according to the manufacturer's recommended pressure.

Can any spare wheel be fitted to any car?

No. The wheel dimensions, bolt pattern, load capacity and other specifications must be compatible with the vehicle. Use only a spare approved or specified for the vehicle.

What should you do after fitting a spare wheel?

Drive cautiously, respect any temporary-wheel restrictions and have the damaged tyre repaired or replaced as soon as reasonably possible.

Is carrying a spare tyre compulsory?

This depends on the country and vehicle category. Some jurisdictions require particular breakdown equipment, while others allow vehicles to operate without a spare wheel.

160. Flat tyre

A flat tyre is a tyre that has lost enough air pressure that it can no longer support the vehicle or operate safely. It can result from a puncture, damaged valve, damaged wheel, tyre failure or a gradual air leak.

A flat tyre can seriously affect steering, braking and vehicle stability. The driver should reduce speed smoothly, avoid sudden steering or braking and stop in a safe place as soon as possible rather than continuing to drive on the damaged tyre.

Flat tyre
Damaged and deflated car tyre.
Wikimedia.org • Stian Martinsen • CC BY-SA
What should you do if a tyre becomes flat while driving?

Keep control of the vehicle, reduce speed gradually and move to a safe stopping place. Avoid sudden braking or steering because the vehicle's handling may be significantly affected.

Can you continue driving on a flat tyre?

Normally no. Driving on a deflated tyre can damage the tyre and wheel and can make the vehicle difficult to control. Some run-flat tyres permit limited continued driving under specified conditions, so the manufacturer's instructions should be followed.

What can cause a flat tyre?

Common causes include punctures, damaged valves, cracked or damaged wheels, tyre sidewall damage and gradual air leakage. Regular tyre-pressure and condition checks can help identify some problems before complete pressure loss occurs.

161. Jack

A jack is a portable lifting device used to raise part of a vehicle off the ground, commonly when changing a wheel. Vehicle jacks can be mechanical, hydraulic or electrically operated.

A jack should only be used at the lifting points specified by the vehicle manufacturer and on a firm, stable surface. The parking brake should be applied and the vehicle secured against movement before lifting.

Jack
Changing a tyre of a Citroën Xsara with a jack to lift the vehicle.
Wikimedia.org • Santeri Viinamäki • CC BY-SA
What is a vehicle jack used for?

A jack is used to lift part of a vehicle so that a wheel can be removed or certain maintenance tasks can be performed.

Where should a jack be placed?

The jack should only be positioned at the lifting points specified by the vehicle manufacturer. Using an unsuitable location can damage the vehicle or cause it to become unstable.

Is it safe to work underneath a vehicle supported only by a jack?

No. A jack is primarily a lifting device and should not be relied upon as the sole support when working underneath a raised vehicle. Appropriate supporting equipment should be used for work beneath the vehicle.

162. Vehicle inspection

A vehicle inspection is an official check to determine whether a vehicle is safe, roadworthy and compliant with applicable technical and environmental requirements. Depending on the country and type of vehicle, inspections may check the brakes, tyres, steering, suspension, lights, emissions, identification and other safety-related components. Inspection rules and intervals vary between countries: some vehicles require regular periodic inspections, while others may also need an inspection after major modifications, an accident, importation or a change of ownership.

Vehicle inspection
Roller brake test at a vehicle inspection station.
Wikimedia.org • Roman Zázvorka • CC BY-SA
What is a vehicle inspection?

A vehicle inspection is an official examination of a vehicle to check whether it meets applicable safety, technical and environmental requirements.

What is checked during a vehicle inspection?

The inspection may include the brakes, tyres, steering, suspension, lights, vehicle identification and emissions. The exact inspection points depend on the country, vehicle type and type of inspection.

How often does a vehicle need to be inspected?

The inspection interval depends on the country and type of vehicle. Some countries require annual inspections, while others use longer intervals based on the vehicle's age, use or condition.

What happens if a vehicle fails the inspection?

A vehicle that does not meet the required standards may need to be repaired and presented for another inspection. Serious defects may restrict or prohibit the vehicle from being used until they are repaired.

Do all countries have the same vehicle inspection rules?

No. Vehicle inspection systems differ between countries, including which vehicles must be inspected, how often inspections are required and which technical standards are checked.

Do electric vehicles need a vehicle inspection?

In countries with periodic vehicle inspections, electric vehicles are generally also subject to inspection. Some inspection points differ because electric vehicles do not have a conventional combustion engine or exhaust-emission system.

163. Key

A key is a device used to unlock a vehicle and authorise its operation. Traditional vehicle keys use a mechanical blade, while modern vehicles commonly use electronic transponders, remote-control key fobs or keyless systems that communicate electronically with the vehicle.

Many modern keys work together with an immobiliser that prevents the engine or propulsion system from being activated unless an authorised key is detected. Replacement or duplicate keys may therefore need to be electronically programmed to the vehicle.

Key
Car keys of a Porsche, Ferrari and BMW.
Wikimedia.org • chen chin • CC BY
What does a modern car key do?

A modern car key can unlock and lock the vehicle and authorise the engine or electric propulsion system to start. It may use a mechanical blade, electronic transponder, remote-control functions or a keyless system.

What is a transponder key?

A transponder key contains an electronic identification device that communicates with the vehicle's immobiliser. If the correct code is not recognised, the vehicle normally prevents the engine or propulsion system from being started.

What should you do if you lose a vehicle key?

Use a spare key if available and arrange a replacement through an appropriate dealer, locksmith or vehicle specialist. Modern replacement keys often need to be programmed to the vehicle's electronic security system.

164. Dashboard

The dashboard is the area in front of the driver that displays important information about the vehicle and provides access to controls and warning indicators. It commonly includes the speedometer, fuel or battery level, warning lights, indicators and information about the engine, brakes and safety systems. Modern vehicles may use a digital instrument display instead of traditional gauges. Drivers should understand the main dashboard symbols and respond appropriately when a warning light appears.

What is a car dashboard?

The dashboard is the panel in front of the driver that displays vehicle information and contains controls, gauges and warning indicators.

What information is shown on the dashboard?

A dashboard may show the speed, fuel or battery level, engine information, warning lights, turn indicators and safety-system status. The exact display depends on the vehicle.

What do dashboard warning light colours mean?

Colours generally indicate the importance or function of a dashboard light. Red often indicates a serious warning, yellow or amber usually indicates caution, and green or blue commonly indicates that a system is active. Symbols and meanings can differ between vehicles, so consult the vehicle manual.

What should I do if a dashboard warning light comes on?

Identify the warning and follow the instructions in the vehicle manual. A red warning light may require you to stop safely as soon as possible, while other warnings may indicate that the vehicle should be checked or repaired.

What is the instrument cluster?

The instrument cluster is the part of the dashboard directly in front of the driver that contains the main gauges, displays and warning lights.

Can a dashboard be completely digital?

Yes. Many modern vehicles use a digital dashboard or digital instrument cluster that displays vehicle information on one or more electronic screens instead of traditional analogue gauges.

165. Windscreen wiper

A windscreen wiper is a device that removes rain, snow, dirt and other moisture from a vehicle’s windscreen to maintain a clear view of the road. Most vehicles use electrically powered wipers with replaceable rubber blades and several operating speeds, often together with a windscreen washer system. Drivers should replace worn or damaged wiper blades when they leave streaks, skip across the glass or no longer clean the windscreen effectively.

Parallelogram windscreen-wiper mechanism on a Porsche 904.
Wikimedia.org • Lothar Spurzem • CC BY-SA
What is a windscreen wiper?

A windscreen wiper is a device that moves across the windscreen to remove rain, snow, dirt and moisture so the driver can maintain a clear view of the road.

Why are windscreen wipers important?

Windscreen wipers help maintain clear visibility in bad weather and when the windscreen becomes dirty. Poor visibility can make it harder to detect traffic, pedestrians, signs and hazards.

When should windscreen wiper blades be replaced?

Wiper blades should be replaced when they are worn, cracked, damaged or no longer clean the windscreen effectively. Common signs include streaking, skipping, squeaking or areas of the windscreen remaining wet.

What is the windscreen washer system?

The windscreen washer system sprays cleaning fluid onto the windscreen so the wipers can remove dirt and improve visibility.

Can you drive with broken windscreen wipers?

Driving with defective windscreen wipers can be unsafe and may be illegal where functioning wipers are required. The driver must be able to maintain adequate visibility through the windscreen.

Do cars have a rear window wiper?

Many vehicles have a rear window wiper, especially hatchbacks, estate cars and SUVs. Whether one is fitted or legally required depends on the vehicle design and applicable regulations.

166. Doors

Doors provide access to the vehicle and help protect occupants while the vehicle is moving. They must open and close correctly, remain securely closed during driving and have functioning hinges, catches and locking mechanisms. Damaged or loose doors can create a serious safety risk, especially if they can open unexpectedly or cannot be closed properly.

Open car door from a Honda Civic Type R.
Wikimedia.org • Guyon • CC BY
Why are vehicle doors important for safety?

Vehicle doors help protect occupants and keep them safely inside the vehicle. They should close securely and must not open unexpectedly while driving.

What parts of a vehicle door should work correctly?

The door, hinges, catches, locking mechanism and surrounding structure should be secure and in good condition so the door can open and close properly.

Can you drive with a door that does not close properly?

A door that cannot remain securely closed can be dangerous and may make the vehicle unroadworthy. It should be repaired before the vehicle is used.

Are sliding doors checked differently from normal doors?

The basic requirement is the same: the door must open and close correctly and remain securely closed. The exact inspection method can depend on the type of door and vehicle.

Can damaged door hinges be dangerous?

Yes. Damaged, loose or badly worn hinges can prevent a door from closing correctly or allow it to move unexpectedly.

167. Glovebox

A glovebox, also called a glove compartment, is a storage compartment built into the dashboard in front of the passenger seat. It is commonly used to keep vehicle documents, the owner’s manual and other small items within easy reach. The glovebox should be kept closed while driving so that it does not obstruct passengers or allow loose objects to fall into the vehicle. Avoid storing valuables or items that can be damaged by the high temperatures that may develop inside a parked car.

An open glovebox with owner's manual and documents.
Wikimedia.org • Q4RadioGuy • CC BY
What is a glovebox?

A glovebox is a storage compartment in the dashboard, usually located in front of the passenger seat. It is also called a glove compartment.

Why is it called a glovebox?

The name comes from the early use of the compartment for storing driving gloves. Today it is commonly used for vehicle documents and other small items.

What can you keep in a glovebox?

A glovebox is commonly used for vehicle documents, the owner’s manual and small useful items. What should be kept in the vehicle depends on local legal requirements and personal preference.

Should the glovebox be closed while driving?

Yes. Keeping the glovebox properly closed while driving prevents it from obstructing the passenger area and helps stop loose objects from falling out.

Should valuables be kept in the glovebox?

It is generally better not to leave valuable or sensitive items in an unattended vehicle, as a glovebox does not provide strong protection against theft.

Can a glovebox become hot?

Yes. The interior of a parked vehicle can become very hot, and the glovebox can also heat up. Avoid storing heat-sensitive or potentially dangerous items there.

168. Visibility

Visibility is the ability of a driver to see the road, other road users and potential hazards clearly, while also making the vehicle visible to others. Visibility can be reduced by darkness, fog, rain, snow, dirty or misted windows, glare and objects that obstruct the driver’s view. Drivers should keep windows, mirrors and lights clean, remove anything that blocks their field of vision and use the appropriate vehicle lights when visibility is reduced.

Visibility
Experimental long-exposure photograph of moving car traffic.
Wikimedia.org • Rick Doble • CC BY-SA
What does visibility mean when driving?

Visibility describes how clearly a driver can see the road, traffic and hazards and how easily other road users can see the vehicle.

What can reduce visibility while driving?

Visibility can be reduced by darkness, fog, rain, snow, glare, dirty or misted windows and objects that obstruct the driver’s view.

How can you improve visibility while driving?

Keep the windscreen, windows, mirrors and lights clean, remove condensation or ice before driving and use the appropriate lights when conditions require them.

Can objects inside a vehicle obstruct visibility?

Yes. Objects placed on the dashboard, windscreen or elsewhere around the driver can block part of the field of vision and make it harder to detect road users or hazards.

What should you do when visibility is poor?

Reduce your speed, increase your following distance and use the appropriate lights. Make sure you can see far enough ahead to react safely to traffic and obstacles.

Why are mirrors important for visibility?

Mirrors extend the driver’s view to the rear and sides of the vehicle. They should be clean and correctly adjusted, although drivers must still check blind spots where necessary.

169. Rain

Rain can reduce visibility, tyre grip and vehicle control while increasing stopping distances. Water on the road can also cause aquaplaning, where the tyres lose contact with the road surface. Drivers should reduce speed, increase their following distance, avoid sudden steering or braking and use the appropriate lights when visibility is reduced. Extra care is needed during heavy rain and when water collects in wheel tracks or on poorly drained roads.

How does rain affect driving?

Rain can reduce visibility and tyre grip, increase stopping distances and make it more difficult to control the vehicle safely.

What is aquaplaning?

Aquaplaning occurs when a layer of water builds up between the tyres and the road, causing the tyres to lose contact with the road surface and reducing steering and braking control.

How should you drive in heavy rain?

Reduce speed, increase your following distance and use smooth steering, acceleration and braking. Use the appropriate lights and be prepared for reduced visibility and standing water.

Why should you increase the following distance in rain?

Wet roads can increase the distance needed to stop. A larger following distance gives you more time and space to react safely.

What should you do if the vehicle starts aquaplaning?

Remain calm, ease off the accelerator and avoid sudden braking or steering. Make smooth corrections until the tyres regain contact with the road.

Should you use headlights in rain?

Lighting requirements vary between countries. Drivers should use the lights required by local traffic rules whenever rain or other conditions reduce visibility.

170. Fog

Fog can greatly reduce visibility and make it difficult to judge speed, distance and the position of other road users. Drivers should reduce speed, increase their following distance and use the appropriate lights without dazzling others. Avoid relying only on the vehicle ahead as a guide, and be prepared for sudden changes in visibility. When fog is very dense, stopping in a safe place may be the best option.

Why is fog dangerous when driving?

Fog can greatly reduce visibility and make it harder to judge speed, distance and the movement of other road users.

How should you drive in fog?

Reduce speed, increase your following distance and use the appropriate lights. Drive so that you can stop safely within the distance you can clearly see.

Should you use high-beam headlights in fog?

Usually not. High beams can reflect from the water droplets in fog and make visibility worse. Use the lighting permitted and recommended under local traffic rules.

When should fog lights be used?

Fog lights are intended for conditions where fog or similar weather significantly reduces visibility. The exact rules for front and rear fog lights vary between countries.

Should you follow the lights of the vehicle ahead in fog?

No. You should maintain your own safe speed and following distance. Following another vehicle too closely can be dangerous because visibility and stopping distance remain limited.

What should you do if fog becomes extremely dense?

If visibility becomes too poor to continue safely, slow down and consider stopping at a safe place away from moving traffic until conditions improve.

171. Hail

Hail can reduce visibility, make the road slippery and create sudden hazardous driving conditions. Hailstones may accumulate on the road and reduce tyre grip in a similar way to ice or loose material, while larger hailstones can also damage windscreens and vehicle bodywork. Drivers should reduce speed, increase their following distance, avoid sudden steering or braking and, when conditions become severe, consider stopping at a safe place until the hailstorm passes.

Why is hail dangerous when driving?

Hail can reduce visibility and tyre grip, make the road slippery and distract drivers because of the sudden noise and impact of hailstones.

How should you drive during a hailstorm?

Reduce speed, increase your following distance and use smooth steering and braking. If the hail becomes severe or visibility is very poor, consider stopping at a safe place away from moving traffic.

Can hail make a road slippery?

Yes. Hailstones can collect on the road and create a slippery surface with reduced tyre grip, particularly when mixed with rain or melting ice.

Can hail damage a vehicle?

Yes. Large hailstones can damage windscreens, windows, mirrors and vehicle bodywork. Severe hail can also reduce visibility if glass becomes cracked or damaged.

Should you use headlights during hail?

Use the lights required by local traffic rules when hail or other weather reduces visibility. Lighting requirements vary between countries.

Is it safer to stop during severe hail?

If visibility or road conditions become too dangerous, it may be safer to stop at a suitable place away from moving traffic and continue when conditions improve.

172. Sunlight

Sunlight can reduce visibility when the sun is low in the sky or when bright light reflects from wet roads, snow, buildings or other vehicles. Sun glare can make traffic lights, signs, pedestrians and other road users difficult to see. Drivers should reduce speed when necessary, keep the windscreen clean, use the sun visor or suitable sunglasses and leave extra space to react to hazards that may be temporarily hidden by glare.

Sunlight
Sunrise over a street in Cabo San Lucas. (Baja California Sur, Mexico)
Wikimedia.org • Frank Contreras Cardenas • CC BY-SA
Why can sunlight be dangerous when driving?

Bright or low sunlight can cause glare and temporarily reduce visibility, making traffic lights, signs, pedestrians and other road users more difficult to see.

When is sun glare most likely to cause problems?

Glare is often strongest when the sun is low in the sky, particularly around sunrise and sunset, and when sunlight reflects from wet roads, snow, glass or other bright surfaces.

What should you do when sunlight makes it difficult to see?

Reduce speed and increase your following distance so you have more time to react. Use the sun visor where helpful and avoid continuing at a speed that is too high for the available visibility.

Can a dirty windscreen make sun glare worse?

Yes. Dirt, grease, dust and streaks on the glass can scatter bright sunlight and make glare much worse. Keep the windscreen clean inside and outside.

Can sunglasses help while driving in bright sunlight?

Suitable sunglasses can reduce glare and improve visual comfort in bright conditions. They should not be so dark that they significantly reduce visibility, especially when entering tunnels or shaded areas.

Does a sun visor improve visibility?

Yes. A correctly positioned sun visor can block direct sunlight without unnecessarily obstructing the driver’s view of the road.

173. Sunglasses

Sunglasses can reduce glare and improve visual comfort when driving in bright sunlight, especially when the sun is low or reflects from wet roads, snow or other surfaces. Drivers should choose lenses that allow traffic lights, signs and other road users to remain clearly visible. Very dark lenses can reduce visibility in tunnels, at night or in changing light conditions, so sunglasses should be removed when they make it harder to see the road safely.

Sunglasses
Canadian musician Daniel Wesley wearing sunglasses.
Wikimedia.org • Vancouver 125 • CC BY
Can sunglasses help when driving?

Yes. Sunglasses can reduce glare and improve visual comfort in bright sunlight, making it easier to see the road and surrounding traffic.

When are sunglasses most useful while driving?

They are particularly useful when the sun is low in the sky or when bright light reflects from wet roads, snow, glass or other surfaces.

Are very dark sunglasses suitable for driving?

Very dark lenses can reduce the amount of light reaching the eyes and may make it difficult to see in tunnels, shade, poor weather or at night. Sunglasses should not interfere with safe visibility.

Can you wear sunglasses at night?

Sunglasses generally reduce available light and can therefore make it harder to see at night. They should not be worn when they significantly reduce visibility.

Are polarised sunglasses useful for driving?

Polarised lenses can reduce reflections from roads and other flat surfaces, but they may make some digital displays or screens harder to read. Drivers should make sure all essential instruments remain clearly visible.

Should sunglasses be removed when entering a tunnel?

If the lenses make the darker environment difficult to see, remove the sunglasses when it is safe to do so. Drivers should always maintain adequate visibility as lighting conditions change.

174. Salt

Salt is commonly used for deicing and anti-icing roads in winter. It lowers the freezing point of water, helping to prevent ice from forming or to melt existing snow and ice. Road authorities may spread dry salt, wet salt or brine before or during freezing conditions. Salt improves road safety, but drivers should still reduce speed and adapt to slippery conditions because treated roads can remain hazardous, especially during heavy snowfall, freezing rain or very low temperatures.

Why is salt used on roads in winter?

Salt helps lower the freezing point of water, making it harder for ice to form and helping existing snow or ice melt.

What is the difference between deicing and anti-icing?

Anti-icing means treating the road before ice forms, while deicing means applying salt or another treatment after snow or ice is already present.

What is road brine?

Brine is a solution of salt and water that can be sprayed onto roads before freezing conditions occur. It helps the salt begin working quickly and can reduce ice formation.

Does salt make an icy road completely safe?

No. Salt can improve grip by reducing snow and ice, but treated roads can still be slippery. Drivers should continue to reduce speed and increase their following distance.

Does road salt work in every temperature?

No. The effectiveness of salt decreases as temperatures become very low. Road authorities may use different treatments or methods depending on the weather and road conditions.

Can road salt damage a vehicle?

Repeated exposure to road salt can contribute to corrosion of metal parts, particularly underneath the vehicle. Washing accumulated salt from the vehicle can help reduce this effect.

175. Air conditioning

Air conditioning helps control the temperature and humidity inside a vehicle and can improve comfort and visibility. In hot weather it cools the passenger compartment, while in damp conditions it can help remove moisture from the air and clear mist from the windows more quickly. Drivers should use the system in a way that keeps the interior comfortable without creating large temperature differences, and the system should be maintained so that it continues to work effectively.

Air conditioning button in a car.
Wikimedia.org • Mattes • CC0
What does air conditioning do in a car?

Air conditioning cools and dehumidifies the air inside the vehicle, helping improve comfort and reduce moisture on the windows.

Can air conditioning help demist the windscreen?

Yes. Because air conditioning removes moisture from the air, it can help clear condensation from the windscreen and windows more quickly.

Should air conditioning be used in winter?

Yes. Air conditioning can still be useful in winter because it reduces humidity inside the vehicle and can help demist the windows.

Does air conditioning increase fuel or energy consumption?

Yes. Operating the air-conditioning system requires energy and can increase fuel or electricity consumption, although the effect depends on the vehicle, system and conditions.

Should a car's air conditioning be maintained?

Yes. Regular use and maintenance can help keep the system effective. A poorly functioning system may cool less efficiently or fail to remove moisture properly.

Can you drive without air conditioning?

Yes, in many vehicles and countries air conditioning itself is not required. However, the driver must still maintain adequate visibility and safe conditions inside the vehicle.