Explanation: Long white lines with short gaps mean there's a hazard ahead. Often a warning sign will show you the nature of the hazard. Don't cross the line unless you can see the road is clear well ahead and you wish to overtake or turn off.
Category: Band 2 traffic signs and signals
References: The official DVSA guide to driving: section 6, Highway code: rule 127, Highway code: page 114, Know your traffic signs: page 62