AKUREYRI, Iceland — Police in Iceland have a warning for visitors: Beware our roads in the winter. Spending a clear winter night under an Arctic sky lit up by spectacular streaks of color from the Northern Lights is an often-cited “bucket-list” experience among the reasons more people are visiting Iceland, especially its northern region. The remote region on the edge of the Arctic Circle is one of the best places in the world to spot the colorful phenomenon. But police say many foreign visitors lack the experience and expertise to handle Iceland’s wintry road conditions.