Which characteristic defines the NEMA TS-1 standard for traffic signal controllers?

The NEMA TS-1 standard for traffic signal controllers is designed to ensure universal compatibility among various equipment and devices involved in traffic management systems. This compatibility is crucial for effective interoperability, whereby different manufacturers' products can work seamlessly together, facilitating easier upgrades, maintenance, and system integration.

By promoting universal compatibility, NEMA TS-1 allows municipalities and agencies to select from a variety of vendors and technologies without being locked into a single manufacturer's ecosystem. This flexibility can lead to cost savings and improved functionality as agencies can leverage the best available technologies for their specific needs without technical barriers.

In contrast, other characteristics mentioned, such as a focus solely on cost reduction, would not align with the standard’s goal of ensuring interoperability and flexibility. Similarly, a specification for a single configuration or encouragement of proprietary designs would limit the overall effectiveness and adaptability of traffic signal systems, which is not the purpose of the NEMA TS-1 standard.