In a transit system, what is typically the highest voltage present?

In a transit system, the highest voltage present is typically 600 volts DC. This voltage level is commonly used in various forms of electric rail transportation, such as light rail systems and subways, due to its efficiency in powering electric motors for traction. The 600 volts DC is sufficient for operating trains and can effectively convert electrical energy into mechanical energy without the need for excessively high voltage systems, which could pose greater safety risks and wiring complexities.

While 120 volts AC and 240 volts AC are standard voltages used in residential and commercial electrical systems, they are not sufficient for the power requirements of a transit system. Additionally, 1000 volts DC, while it is used in some specialized applications, is not standard for general train operations and would represent a higher voltage than what is typically required for everyday transit systems.

Therefore, the selection of 600 volts DC as the correct answer reflects its established and practical use in the rail transit industry for providing adequate power while maintaining safety and reliability.