Complex sentence: Gravel roads are often found in cold climates because they are less vulnerable to freeze/thaw damage than asphalt roads and also because the inferior surface of gravel is not an issue if the road is covered by snow and ice for extended periods.
Split into simpler sentences: Gravel roads are often found in cold climates because they are less vulnerable to freeze/thaw damage than asphalt roads. The inferior surface of gravel is not an issue if the road is covered by snow and ice for extended periods.