Usually the centre of the road is marked by a broken white line, with lines that are shorter than the gaps. However, when the lines become longer than the gaps this is a hazard warning line. Look well ahead for these, especially when you are planning to overtake or turn off. If there is a continuous double white line down the centre of the road, this means it would be dangerous to overtake. You are only allowed to cross continuous lines to pass a stationary vehicle, a cyclist, horse or road maintenance vehicle travelling at 10mph or less, and to enter premises or a side road.