Electrician's Licensing Practice Exam

What is the required clearance for a 400-amp service drop across a major roadway?

1. 12 ft.

2. 15 ft.

3. 18 ft.

4. 20 ft.

The correct answer is: 18 ft.

The required clearance for a 400-amp service drop across a major roadway is established to ensure safety and accessibility for both vehicular and pedestrian traffic. A clearance of 18 feet is necessary for service conductors to minimize the risk of electrical hazards and to accommodate the height of large vehicles such as buses and trucks that may travel under the service drop. This height requirement encompasses considerations such as maintaining a safe distance to avoid accidental contact with the conductors, which could lead to severe injuries or fatalities. It also accounts for potential variations in the roadway surface due to factors like snow, wear, or construction activities that may affect the effective height of vehicles. Other clearance options, such as 12 feet, 15 feet, or 20 feet, do not meet the established safety criteria for service drops, either falling short of necessary protection in the case of larger vehicles or exceeding what is typically mandated, affecting the practical implementation of the installation. Therefore, 18 feet is the standard minimum clearance for this situation, ensuring compliance with safety regulations and enabling safe operation in areas with higher vehicular traffic.