答案：

　　When smart traffic lights are set up and traffic management software is installed, the number of green lights on each street has been optimized to avoid traffic congestion as well as to allow ambulances to reach incidents without any delay.

　　* software (不可数名词)软件;托福写作常用不可数名词，还有：education, transportation, equipment, evidence, globalization, feedback, homework, advice, information等。