During which decade were solid-state electronic controllers developed to replace electro-mechanical controllers?

Answer: B — 1970's

The development of solid-state electronic controllers as a replacement for electro-mechanical controllers took place during the 1970s. This technological shift was significant because solid-state devices offered greater reliability, efficiency, and features compared to their electro-mechanical counterparts. Solid-state electronics allowed for more compact and versatile designs, which improved the overall functionality of traffic signal systems. They also provided enhancements such as better timing precision and the ability to integrate with new technologies, paving the way for advanced traffic management solutions in the future. This transition became an important milestone in the evolution of traffic signal control systems during that decade.