Complex sentence: Railtrack did not know how many other cases of rail fatigue around the network could lead to a Hatfield-like accident and consequently imposed over 1,800 emergency speed restrictions and instigated a nationwide (and costly) track replacement programme.
Split into simpler sentences: Railtrack did not know how many other cases of rail fatigue around the network could lead to a Hatfield-like accident. Railtrack imposed over 1,800 emergency speed restrictions and instigated a nationwide (and costly) track replacement programme.