Complex sentence: At the time, the Chase train wreck was Amtrak's deadliest crash ever; in 1993, however, the Big Bayou Canot train disaster in Alabama resulted in a much larger death toll.
Split into simpler sentences: At the time, the Chase train wreck was Amtrak's deadliest crash ever. In 1993, however, the wreck at Big Bayou Canot in Alabama resulted in a much larger death toll.