Complex sentence: Then the new extension to the new platform and ticket booth was built and a crossover was built in the middle of the 1/2 mile loop to complete the main layout.Sprung switched allow for doubling back over most of the line.
Split into simpler sentences: Then the new extension to the new platform and ticket booth was built and a crossover was built in the middle of the 1/2 mile loop to complete the main layout. Sprung switches allow for doubling back over most of the line.