A highway divider is a physical barrier that separates two lanes of traffic on a highway. The most common type of highway divider is a LANE, which is a four-letter word. A MEDIAN is another type of highway divider, which is a six-letter word. A whiteline is a more advanced type of highway divider, which is a nine-letter word. Finally, a doublewhiteline is the most advanced type of highway divider, which is a fifteen-letter word.