Lighting-up Time

In the United Kingdom there is a legally enforced lighting-up time, defined as from one half-hour after sunset to one half-hour before sunrise, during which all motor vehicles on unlit public roads (but not parked) must use their headlights.

Lighting-up time was first introduced in the nineteenth century in local by-laws and enforced nationally by the Lights on Vehicles Act of 1907. The Road Lighting Act of 1942 stipulated 1 hour after sunset/ before dawn. It was amended to 30 minutes by the Road Traffic Act of 1956 because of the increasing speed of traffic. These were the required times for showing all lights on all vehicles, including bicycles and horse drawn carts, hence the name lighting-up time.

The (still current) Road Vehicles Lighting Regulations, 1989 tightened the requirements further. Lighting-up time is retained as the required period for use of motor vehicle headlights on roads without lit streetlights, but with that exception, all vehicles must now keep conspicuity lights lit during the longer period of sunset to sunrise (unless parked, either in a designated parking place or facing the same way as adjacent traffic and more than 10 m from the nearest junction on a road with a speed limit not exceeding 30 mph). The conspicuity lights required are "front and rear position lamps" (side and tail lights) plus, for large vehicles, side marker lamps and end-outline marker lamps and, for motor vehicles, rear number plate lights.

Headlights are also required at other times when visibility is restricted, e.g. by fog, rain, snow, overcast sky or smoke. They should also be used in tunnels.

Streetlights are usually set to come on automatically near the beginning of lighting-up time, although modern lamps monitor the light level and turn on when this gets too low, and so are influenced by weather. They may also be set to switch off automatically when road usage is reduced, often at midnight, although currently most stay on until about the end of lighting-up time. Headlamps must be used during lighting-up time unless streetlamps are alight.

Sunrise and sunset are defined by the Road Vehicles Lighting Regulations as local sunrise and sunset so the times are different in different parts of the UK; they are earlier in the east and later in the west, and vary more with the seasons in northerly locations than in southerly locations.

Lighting-up times were formerly commonly displayed in national and local newspapers in the UK and announced on national and local radio stations, but the widespread adoption of street lighting has rendered this largely redundant. As a result, most of the previous sources no longer provide them, but may still provide sunrise / sunset times.