Part-time engineers develop and monitor the construction of the functional aspects of a product, structure, or system for their company or client. Unlike full-time engineers, part-time engineers typically work thirty hours or less a week. Specific job duties vary, depending on their specific engineering industry. For example, civil engineers design, construct, and maintain large infrastructure projects for municipalities and other agencies, such as bridges, highways, and airports. As the structures wear down, civil engineers reevaluate the needs of the area and may redesign the current structure or create a new system. Electrical engineers draft plans for electrical systems. Once the systems are created and installed, electrical engineers may also be responsible for maintaining the system to ensure it continues to run efficiently.