Recommended Practice

UPS/BBU systems are not currently required at signalized intersections; however, the 2011
Texas Manual on Uniform Traffic Control Devices
 (TMUTCD), provides guidance that “Except for traffic control signals interconnected with light rail transit systems, traffic control signals with railroad preemption or coordinated with flashing-light signal systems should be provided with a back-up power supply.” Even though back-up power is not currently required, there are many locations that can benefit from the installation of battery backup systems.
The decision to install UPS/BBU systems is at the discretion of each district, but should be based on a study of conditions at the proposed intersection. In deciding whether to install a UPS/BBU system at an intersection, there should be an evaluation of the conditions at the intersection. Installation of UPS/BBU systems should be based on a priority established by the characteristics or conditions at the location. Locations where UPS/BBU systems are most beneficial include:
  • intersections with unique geometry such as wide medians, conflicting left turns that require lead-lag operation, protected-only left-turn operation, or split phasing where right-of-way assignment is difficult for a four-way stop operation
  • intersections over capacity with heavy directional traffic flow
  • intersections with a history of signal malfunction due to power quality or reliability issues
  • intersections on high volume roads (total volume of all approaches in excess of 20,000 ADT)
  • intersections with rail preemption
  • intersections with emergency preemption, or intersections near fire stations (within 1200 ft.)
  • intersections with signal repair response time in excess of 30 minutes
  • intersections with 1320 ft. proximity to another intersection with UPS/BBU
  • intersections that are part of a coordinated system, or are part of a corridor that functions as a major arterial in an urbanized area
  • intersections with high speed approaches.
Intersections that consistently experience trouble with utility line power, have railroad interconnect for preemption, or have a unique geometry, are high in priority. Intersections that rarely have utility power issues and/or have simple geometry would be considered low priority and would not be good candidates for a UPS/BBU system. A UPS Guidelines Worksheet is available from the Traffic Safety Division that can be used to develop intersection priority for installation of UPS/BBU systems. Not all intersections will have all the conditions listed, and in some cases, the engineer may consider the relative importance of the conditions at the intersection a higher priority than listed on the spreadsheet.
Documentation detailing the criteria for the installation that was considered should be maintained by district traffic operations for each location where a UPS/BBU system is installed.
Installation of UPS/BBU for new traffic signal locations should be identified during the initial design development process.