ROAD safety organisation GEM Motoring Assist is urging motorists to ensure they're as visible as possible.

The advice follows complaints and observations from GEM members across the country about vehicles with dangerous lighting defects.

There are large numbers of drivers using vehicles with defective headlights, causing a significant risk to themselves and others on dark days and wintry nights.

Cars with only one headlight mean the drivers have only 50 per cent of the light they should have, and the missing light risks causing confusion to other road users who may think there's a motorbike approaching, says GEM.

Parking and slow speed manoeuvring is also made riskier, as the absence of light means impacts with parked vehicles, walls, posts and trees are much more likely.

A GEM spokesperson urged drivers to use dipped headlights on every journey and not to assume that a car's automatic light settings would guarantee safety and visibility.

"Drivers who consider that lights are for use only in darkness are causing danger to themselves and others," she said.

"Many drivers are making journeys on gloomy winter days without switching their lights on. Using dipped headlights for all journeys at this time of year is the safest option.

"Unfortunately, some drivers are making themselves harder to spot from behind when daytime visibility is reduced, because they're relying on automatic lighting systems and front-only daytime running lights. These lights are designed purely so that a vehicle can be seen; they do little to illuminate the road ahead.

GEM has issued the following tips for drivers to make sure their lights are in order:

1. Carefully check your lights before setting off, to ensure they're free from dirt and ice, and to ensure they're working properly. Dirt, ice, snow and frost reduce the effectiveness of a car's lights and it's an offence to drive with obscured lights.

2. Get any defective bulbs replaced immediately. A bulb failure on your car compromises your safety and increases risk to other road users.

3. See and be seen. Look after your vehicle's lights and you will be helping to make the roads safer.

4. Use dipped headlights for every journey in winter months. Don't rely on daytime running lights, as they won't brighten the road ahead for you and you may find you have no rear lights showing at all.