1.   They also want the trees kept to a height which will not let them block the track should they be blown over.

2.   Soon afterwards the track was blocked again by sand and gravel dumped on it.

3.   At other times, bandits have blocked the track with boulders and couches, or tried to dismantle the railroad ties to force a derailment.

4.   At Vaughn, Miss., the main track was blocked by two freight trains that extended from a siding.

5.   Some roller coasters have the additional protection of infrared light beams that give an alarm when there is someone or something blocking the track.

6.   The effort only stopped when refugees blocked the tracks.

7.   The whole track was blocked by smoke and spinning cars.

8.   At least four convoys have been forced to return to the port after roads and rail tracks were blocked.

9.   But she promised not to block the tracks again.

10.   But on the way back, the driver found the track blocked with rocks and the lid of a water tank.