Complex sentence: By the time the buses have reached the San Salvador historic downtown they would already transported 20,000 passengers, SITRAMSS us a public-private partnership involving the current passenger transport operators, who must purchase the busses.
Split into simpler sentences: By the time the buses have reached the San Salvador historic downtown they will have already transported 20,000 passengers. SITRAMSS is a public-private partnership involving the current passenger transport operators, who must purchase the busses.