Four hours at full load is the effective Australian benchmark, and it is well sourced. Queensland TMR’s MRTS213 requires 4 hours at a 1400 W full test load. Australian traffic controller products in the SCATS ecosystem are built to roughly the same figure, around 4 hours at maximum load for both integrated and external UPS controller families. NZTA’s ITS UPS specification allows 1 to 8 hours determined per site as part of the installation design, based on criticality and fault response capability. Note this differs from the North American pattern, which typically splits full-operation hours from extended flash-mode hours.

Increasingly LiFePO₄, and specified explicitly rather than permitted. TMR’s MRTS213 requires LiFePO₄ with a minimum 10-year life, 4 hours at 1400 W, maximum 80% depth of discharge, 4-hour recharge from maximum DoD, in multiple parallel strings, rack mounted. NZTA permits lead-acid or LiFePO₄ with minimum service lives of 5 and 10 years respectively. Main Roads WA Specification 713 requires maintenance-free batteries with a minimum expected life of 5 years and a maximum 8-hour charge time. The governing product standard across all of them is AS 5715:2015, UPS for roadside devices.

More than most people specify, and it usually matters more than the battery choice. TMR’s MRTS213 requires an IP-rated double-skinned enclosure with ventilation slots, thermostatically controlled fans and a heater, white (N14) heat-reflective paint to AS 2700, and an internal temperature held between 0 °C and 50 °C, with batteries low, controller above and switchboard at top. Main Roads WA requires internal temperature within ±10 °C of outside ambient within a 10–60 °C range, thermostat regulated. The 0 °C minimum with a heater is not incidental: it exists because LiFePO₄ must not be charged below freezing, and both TMR and NZTA have engineered around that explicitly.

Those are the two ends of the same specification and both have to be answered. NZTA states it directly: required battery backup times “shall be met at a temperature of 0 degrees Celsius”, with reduced autonomy acceptable below that. At the hot end, TMR’s 50 °C internal maximum is the design ceiling. LiFePO₄ handles both discharge extremes well, good products retain most capacity at −20 °C on discharge and do not follow the VRLA temperature-life curve at the top end. The constraint is charging below 0 °C, which is why the cabinet heater is a specification item and not an option.

This is now an explicit requirement in the better specifications and it is worth insisting on. NZTA requires that “replacement of any string shall not require removal of the complete UPS or other strings”, with plug-and-socket DC connections and Anderson-type connectors. TMR requires multiple parallel strings, rack mounted, which supports the same outcome. For a network of hundreds of intersections, string-level replaceability is the difference between a routine maintenance visit and a site shutdown with traffic management.

The bar has moved. Main Roads WA requires RS232/RS485 and Ethernet with an industry standard protocol, full web-server management over a secure connection, SNMP v2 or better, non-volatile logging with encrypted credentials, and a front panel displaying battery voltage, charge and discharge current and remaining autonomy time. NZTA now requires SNMPv3, ideally with DHCP, plus volt-free ELV alarm contacts. If you are specifying today, SNMPv3 is the ask, not v2, and “remaining autonomy time” on the front panel is a genuinely useful requirement worth copying.