1.   Drivers have to be on their guard, as faults or signal failures can occur at any time.

2.   It has been a signal failure.

3.   Rookie drivers making mistakes, signal failures, lagging maintenance, and divided management are being blamed for the wave of accidents, equipment failures and shabby service.

4.   The crash was caused by human error or signal failure, said Mike Martino, an investigator for the safety board.

5.   The other signal American failure has been in the former Yugoslavia.

6.   The Olympics may continue to be a success as a financial enterprise, but it is a signal failure as an ethical institution.

7.   Their signal failure, so far, has been to get Kosovars to live with the remaining Serbs.

8.   While early reports indicated that the accident may have been caused by a bomb, officials said later that an initial investigation pointed instead to a signal failure.

9.   Investigators from the state railroad company suspected a signal failure caused the collision on the single line track.

10.   In the past, however, officials have blamed signal failures for similar collisions.