White painted markings
At junctions they indicate priorities. As centre or lane lines they indicate the best line for vehicles to follow. White markings are generally advisory.
Lane arrows are used on the approaches to traffic signalled junctions to indicate which lane should be used for turning and straight ahead movements. Lane arrows are generally not permitted on the approaches to roundabouts.
SLOW markings are used on the approach to a hazard.
Areas of central cross hatching, called "ghost island" markings, are used to reduce accidents by separating oncoming traffic, reducing traffic speed and providing safe right turning areas. These, along with central traffic islands, play a major part in reducing motorcycle accidents.
Double white lines
Continuous white centre line markings must not be crossed
These are often used to prevent overtaking or reduce speeds in roads with poor visibility where there are bends or crests of hills. They are used sparingly so that they have more impact when used.
Rules for using these markings depend on traffic speed and visibility distances.
It is an offence to park in any section of road that is marked with a continuous white line.
Continuous white lines may only be crossed by traffic that is turning right
More information regarding lining can be found in the Highway Code.