The Story of The Car Part 8: Signals and Lights

Signals and Lights.

If glass and mirrors are for taking information, signals and lights are for the giving of information.

Signals should only be given if another road user would benefit. They should help not harm. Unnecessary signals are information clutter. Signals show an intention of purpose, they are not an assertion of rights.

It is your responsibility to ensure what you do is safe both for yourself and other road users. Please note there are no rights of way only an obligation to give way if that avoids an accident.

All signals whether taken or given need to be confirmed by speed and position so as to show they are not taken or given in error.

Speed and Position as a Signal.

Speed and position are a basic signal to the other road user and is sometimes known as the car’s chassis language. A wider view is by reading other vehicles speed and position you are reading the road and the intention of the other road user. Speed and position are in effect a signal regardless of whether a recognised signal is given.

Audible signals.

These are the signals of warning.


The Horn:

  • Used internally in your car as a warning to other road users of your presence
  • Your driving plan should allow for the fact the other road user may be deaf
  • It is not to be used as a rebuke because you may be distracting and making worse the errors of another road user
  • A rebuke to another road user can in certain circumstances be a trigger to road rage
  • Use at night should be also limited to minimise noise pollution
  • At night a flash of the headlights might be more effective


  • These are external to your car and warn you of the presence of an emergency vehicle
  • Pull over where safe and allow them to pass
  • A signal confirming your action may be helpful
  • Beware of pulling over by Traffic Islands or Pedestrian Refuges in the road
  • Your aim is to allow the emergency vehicle through
  • Emergency vehicles have statutory exceptions to certain traffic laws but must show just cause

Personal Signals.

These are hand signals which are driving task related. All drivers should have an understanding of hand signals as they may be used by other road users. Or if your car has a signal failure.

They are also courtesy signals which should be both given and acknowledged. Any hand signal should not be used as a rebuke.


Because driving is such a visually  rich experience most signals are visual. These visual signals are mainly lights and indicators, supplemented by hand and courtesy signals.

The more intense a light is the more it washes out what can be seen round it. This is important in how we use our vehicle lights. Our eyes are drawn to the light, and at night it is the light that we focus on.

All drivers should carry spare bulbs.

The light source is known as the lamp which produces the light. Hence the headlamps are the source and headlights are the product.

The lighting systems will serve 2 purposes:

  • As driving aids, to illuminate for the benefit of the driver.
  • As driving signals, for the benefit of other road users.
  • Sometimes the lights serve both purposes.

For example a reversing light will illuminate the immediate area behind but also inform the other road user that you are in reverse.


As vehicle speeds have increased, so the need to illuminate further ahead has increased.

This has been achieved in 3 ways.

Firstly by the bulb technology:

  • Which produces a more intense pre-focused light
  • The bulbs may contain 2 filaments to provide high and low beam light

Secondly pre-focused parabolic reflectors:

  • This is using shape to take advantage of the pre-focused light
  • The reflectors as well as increasing the light thrown forward also provide passive illumination when parked.

Thirdly better lenses to provide both high and low beam light:

  • A sealed beam turns the whole lamp into a very efficient unit with a long life
  • Because the unit is sealed no dirt or moisture can pollute the lamp
  • The bulb needs no separate glass envelope
  • This means the deposits from the filament are spread over a much larger area which increases the efficiency of the light
  • The downside of a sealed unit is a high replacement cost and light failure in the event of the lens cracking
  • Because it can be difficult to provide both high and low beam from a single unit a four headlamp system is sometimes used
  • Two headlamps for high beam: two for low beam

In a more rural setting the purpose of the lights is illumination of the road for the benefit of the driver.

In a more urban setting with the presence of street lights the purpose of vehicle lights is to illuminate your vehicle for the benefit of other road users.

Some vehicles will have a facility to make the headlights come on automatically. This may be when the windscreen wipers are working or when it starts to get dark.

Your headlights may have to be adjusted when carrying extra load in order not to dazzle any oncoming vehicles. Some cars will do this automatically,  in others it will be a manual adjustment.

The High Beam:

This may be known by other names such as main beam, driving beam or full beam. It shines directly into the road ahead for the purpose of lighting that road. The throw of light will be for a distance of approximately 100 yards or meters depending on the car. This is your safe stopping distance at 70 mph.

The illumination produced by this beam will dazzle an oncoming vehicle which tends to mean that it is used more rural or in low traffic situations. In bad weather this beam will light up fog, snow and rain due to reflection of the droplets. This means you should switch to a low beam to avoid the reflection of the droplets.  

Your speed should be appropriate to the distance you can see to be clear.

The Low Beam:

This is sometimes known as the dipped or passing beam. It will shine ahead but also off to the nearside and down a bit in order not to dazzle the oncoming vehicle. The throw of light will be for a distance of approximately 50 yards or meters dependent on the car.

Headlight bulbs need to be appropriate for the side of the road we drive on. This is because a low beam throws light to the near side. In bad weather the reflection from fog, snow and rain is reduced by using low beam but so is the area illuminated up ahead.

Note: you should always be able to stop in the distance you can see to be clear.

Flashed Headlights.

This is a visual warning of presence only. It may be used where the horn is inappropriate such as at night. Another use is where the background noise means the other road user may not be able to hear a horn. An example of this is overtaking where a quick flash may alert the vehicle being overtaken to your presence and intention.

Also: if a vehicle was about to pull out in front of you. Never assume that a flashed headlight is for your consumption. The message given by a flashed headlight can have different meanings.

Possible meanings are:

  • I am giving way or I am coming through.
  • Speed up or slow down, danger ahead.
  • I am overtaking or there is space for you to pull back in.
  • It may be a curtsy signal or a rebuke.
  • As stated at the beginning of this section headlight flashing is a visual warning of presence only.

Daylight Running Lights.

As any motorcyclist will tell you the one thing that ensures you get seen day or night is an illuminated vehicle light. The further north you are in the world and hence less bright daylight. The more likely that it is a legal requirement to have Daylight Running Lights.

Motorcycle groups are concerned that vehicles with daytime headlights on tend to devalue the benefit of motorcyclists having them. To allow for this, car manufactures are fitting strips of LED lights to reduce confusion with headlamps. If headlights are the eye’s of a car. Day light running lights are it’s eyebrows.

Fog Lights.

These tend to be used more badly in good weather than well in bad weather.

The purpose is to throw a bar of light down to the ground in order to illuminate the foreground and nearside edges. Their use is for when fog, snow, dust, rain or anything that might cause reflection of the projected light from the high beam.

A danger with fog lights is they can do a very good job of illuminating the foreground giving an illusion of safety. But unless you can stop in the distance you can see to be clear you are driving into potential danger.

The colour of the light may be white or yellow. Yellow/amber is used as the colour of warning but also for its greater visibility in adverse conditions. Because of the intensity of the light they may mask other lights. This is a particular problem with brake lights.

Fog lights should not be used when there is no need for them. So visibility should be less than 100 meters before being used. So if you can not see the next lamp post in a built up area you know that you need your fog lights on.

Indicators and Hazards.

These are used for the giving of information. When in use they are flashing amber. They work to the front, rear and side of your vehicle. Yellow/amber is used as the colour of warning but also for its greater visibility in bad conditions.

The indicators work from the indicator arm in the direction of turn which will cancel on the wheel being straightened. Inside the car there will be a flashing light on the dash to draw your attention to the fact the indicators are being used. The flashing effect will normally be speeded up if one of the indicator bulbs is no longer working.

The hazard light button sometimes sits proud either on the dash or steering column for ease of access. It will be a red button that will flash when the hazards are being used. Because of its position either on the dash or steering column it will reflect on to the windscreen when being used. This is to make clear that hazards are operational when the vehicle is moving. When the hazards are being used the indicators will not be available.

Side Lights.

These may be used as an indication of presence in the absence of daylight running lights. In the MOT manual they are called positional lights. They work to the front of your vehicle where they are white and to the rear when they are red.

When the headlamps are in use the sidelights will also be automatically on as an insurance against headlamp failure. They should also be used if the vehicle is parked at night and other road users would benefit. For example: on a country road with no street lights.

Brake Lights.

These are used to inform following road users that your vehicle is slowing or possibly stopping. The light shows red and may also be known as a stop light. It may be a separate light or a brake/side light unit with a dual filament bulb. 

On certain models of vehicles a braking intensity is shown by a greater intensity of light or a flashing of that light. The light may also be supplemented by a high level light centered to the rear windscreen.

Reversing Lights.

These are used to inform other road users and pedestrians that your vehicle is moving backwards. The light is white and can be a single lamp or a double depending on the vehicle.

Other External Lights.

The rear number plate is illuminated whereas the front number plate is not. Large vehicles carry extra lights to indicate extra height and width. Off road vehicle will have extra lights to illuminate the driving task. Emergency vehicles will have the appropriate flashing lights. Specialist working vehicles may have flashing amber lights. Taxis have illuminated top lights to show they are available for hire.

The Interior Light.

This is sometimes known as the dome or courtesy light is centred high to the ceiling of your vehicle. There may be additional ceiling lights located to the front and rear. They will come on when the doors are opened to assist in the finding of seat belts etc. They will go out as the doors are shut but do have the facility to be switched on and off. Your vehicle should not be driven with your interior lights on. Your eyes will adjust to the light in the vehicle rather than to the light outside the vehicle.

Dashboard Lights.

The lights here will illuminate the various instruments. There will be a series of warning lights. The Manufacturer’s Handbook will detail these. There will be a cowling over the top of the dashboard to stop the instrument lights being reflected onto the windscreen at night. The exception to this is normally the hazard light indicator which is sometimes set to the steering column or on top of the dashboard. Besides giving ease of access to that signal, when it is operational and flashing it will reflect to the windscreen.

car instrument panel

Assistance Lights.

These vary in number and location according to make and model. They could include lights to the boot and engine compartment, glove box, door, and ignition.

The Syllabus For Learning To Drive – Signals

Syllabus For Learning To Drive – Darkness

© Liam Greaney