To maintain orderly and safe vehicle, pedestrian and bicycle movements at signalized intersections interconnected with a railroad crossing it is recommended to provide uninterrupted, operation, avoiding black out or flashing red conditions, during a railroad preemption event. The TxDOT standard is to install a uninterruptible power supply/battery back-up (UPS/BBU) system at traffic signals that are interconnected to a railroad crossing. UPS/BBU systems at interconnected traffic signals shall provide at least 4 hours of continuous operation before transitioning to all-red flash operation.