Clearance requirements for overhead service conductors have often proven to be a life or death matter. In many cases, the installer adhered to the NEC minimums without considering the actual conditions. Always use these as a starting point, not as the distance you can get by with in an attempt to save money on masts and supports.
Overhead Service Conductors, Part 2
Know whether the conductors have adequate mechanical strength for the support provided for a given span.