Equally divide polyline feature class

I was wondering if anyone knows a way to divide a cities polyline feature class into equal parts. My task is to divide our local utilities gas mains into equal areas then create polygons from these areas. For example, the city has 500 miles of gas mains. I need to divide the gas mains into 5 groups that contain as close to 100 miles each as possible. The combined area near the center of town will be smaller due to the concentration of gas mains in the area versus the outskirts of town where the mains are more spread out and the area will be bigger. Thanks in advance!