No one bothered to put a traffic blockade in place, as required, and the welding of the tracks could not be completed before the train passed through.
I. The train collapsed injuring many passengers.
II. Signal is required to indicate that the repair work is in progress.
I is an effect of the statement and not the assumption. Thus, I is not implicit. Since no one ‘bothered as required’ is mentioned. It means that signal like traffic blockade is a must to avoid accidents. Thus, II is implicit.