Lighting & Optical Signals: DGT theory test questions in English

Clearance lights mark the full width and height of large vehicles. They are required on every vehicle wider than 2.10 meters. Height over 4 meters or the 2 m by 6 m size is not what triggers the rule.

Vehicle lights are an active safety feature. They let you see hazards and obstacles in time to react and avoid them, and they let others see you. Low beams also do this job, so it's not only high beams, and the lights are clearly useful.

If a turn signal can't be used, a right turn is signaled with the left arm bent at 90° and the hand pointing up. A left turn is signaled with the left arm stretched straight out. There is no arm signal for continuing straight.

High beams are strictly forbidden while the vehicle is stopped or parked, and so is flashing between high and low beams in that situation. Flashing them briefly to warn others of danger is allowed, and tunnels don't ban high beams as such.

Position lights show your vehicle's presence and width. They must be on whenever your high beams, low beams or front fog lights are on. On a well-lit road, parking there does not by itself require them.

Xenon headlights give light close to daylight, light the road better and use less energy. Their low beams reach farther without dazzling oncoming traffic and cause less eye fatigue. They don't increase fatigue or light the road worse.

You may flash your low or high beams briefly, day or night, to warn others and avoid a possible crash. This is allowed on both urban and interurban roads, especially narrow, winding ones. Always avoid dazzling oncoming traffic.

One long, continuous whistle blast from an officer directing traffic means vehicles must keep moving. It does not mean slow down. Short, repeated blasts are the signal for all vehicles to stop.

When oncoming lights blind you, don't look straight at them. Slow down, and stop completely if needed, until you can see well enough to drive safely. Driving on the shoulder or flashing your high beams back only adds risk.

A motorcycle, with or without a sidecar, may have either one centered or two symmetrical white low-beam headlights in front. So it isn't limited to one. Low beams are never fitted at the back.

In tunnels, underpasses, and road sections marked with the tunnel sign, you must use your low beams plus your parking lights (position lights) at any time of day, even if the tunnel is well lit. Having no lights or parking lights alone is not enough.

Officers may immobilize a motorcycle if the rider has no helmet or hasn't fastened it properly. Other reasons include exceeding gas, smoke, or noise limits, or having no mandatory insurance. So "never" is wrong, and the rule isn't limited to the passenger.

Signal a sideways move with the turn signal on the side you're moving toward. If you can't, use your arm. Hold it straight out, palm down, to move toward that side, or bent upward, palm open, to move toward the other side. The turn signal comes first, so the arm isn't preferred, and it isn't the only option.

The signal is only for the sideways move, so turn it off as soon as your vehicle is in its new path. Don't wait until you've finished passing the other vehicle. Don't wait for others to react either.

Between sunset and sunrise, you must use your parking lights (position lights) together with your low beams and the rear license plate light. Parking lights alone are not enough. High beams are not the required lights in town.

You may only use the horn to prevent an accident or to warn others that you're driving on an emergency service. Outside built-up areas, you may also use it to tell the vehicle ahead you intend to pass. Honking about a green light is never allowed, in town or outside it.

Arm signals are official, and they take priority over horn and light signals. If an arm signal contradicts a turn signal, other road users should follow the arm signal.

As part of regular maintenance, check your lighting system's aiming, operation, and condition. Make sure the headlights point in the right direction with the right brightness. You can do this yourself, and checking only the aiming is not enough.

Between sunset and sunrise, all motor vehicles and mopeds must use low beams on urban roads and roads through town (travesías), even poorly lit ones. High beams are not the rule there. Low beams are required whether the road is well lit or not.

Front fog lights are for weather or environmental conditions that greatly reduce visibility, such as fog, heavy rain, snowfall, or clouds of smoke or dust. Darkness alone is not a reason to use them. Using them every night or from sunset to sunrise would only dazzle other drivers.

If a light fails and you have to drive with weaker lighting, you may still drive at night. You must adjust your speed so you can stop within the distance your lights reach. There is no rule that limits you to the nearest shop, and you are not required to stop your trip.

Front fog lights light up the road ahead in bad weather that cuts visibility, such as fog, heavy rain, snow, or clouds of smoke or dust. Driving in an extra lane or entering a tunnel doesn't call for them on its own. In a tunnel you need your low beams.

On a road section affected by fog, you should use your front fog lights, low beams or high beams. If your car has no front fog lights, you must at least turn on your position lights together with your low beams. Leaving out the position lights doesn't meet this minimum, and hazard lights don't replace your headlights.

Yes, it's dangerous. The contrast between the light inside the car and the darkness outside distorts your vision and makes it harder to see the road. The interior light is meant for the cabin, not for driving, so it neither rests your eyes nor prevents glare.