Explanation: Road markings will warn you of a hazard ahead. A single broken line along the centre of the road, with long markings and short gaps, is a hazard warning line. Don't cross it unless you can see that the road is clear well ahead.
Category: Road and traffic signs
References: The official DVSA guide to driving: section 6, Highway code: rule 127, Highway code: page 114, Know your traffic signs: page 62