Typical back-up battery systems provide battery power in case of an outage to a signal for:

Typical backup battery systems for traffic signals are designed to provide power during outages for a practical duration that allows for mitigation of traffic disruptions and safety concerns. The most common duration of 2 to 6 hours strikes a balance between enough time for utility restoration and maintaining signal operation to ensure continued safety on the roads.

This duration is sufficient to allow for temporary disruptions while aiding in reducing the risk of accidents that could occur if signals were to go dark during periods of power loss. A backup timeframe of 2 to 6 hours is widely acknowledged in the industry as practical for ensuring that signals remain operational during anticipated power outages.

Longer durations, such as 6 to 12 hours or 12 to 24 hours, may not be typical for standard traffic signal installations, as they often exceed the needs of most outage scenarios and would require larger or more robust battery systems, which may not be feasible for every installation or budget.