Complex sentence: The Baby Bullet trains reduced travel time by stopping at only four or five stations between San Francisco and San Jose Diridon Station; the faster express trains could overtake slower local trains at the two locations where bypass tracks were installed.
Split into simpler sentences: The Baby Bullet trains reduced travel time by stopping only at five stations between San Francisco and the San Jose Diridon Station. The faster express trains could overtake slower local trains at the two locations where bypass tracks were installed.