Collisions vs. Interference - Rule 7.09
The runner has a right to an unobstructed path while running the bases. The fielder has a right to make a play without interference. The runner has the right to the base path except when the fielder is attempting to field a batted ball or has possession of the ball. Sometimes when a fielder or runner collide, no penalty should be applied. The umpire must judge whether someone's rights were violated. This applies mainly to plays where the throw and the runner are arriving at the same time.
When a runner collides with a fielder attempting to field a batted ball, he should be called out in almost all cases. If a runner collides with a fielder attempting to catch a throw, the umpire must first decide if the collision was intentional, then decide if the act interfered with, impeded, hindered or confused the fielder.
If the runner is legally in the base path and simply running the bases when a collision occurs, he is not out. If he deviates from his path and/or intentionally interferes, he is out.
In sliding to a base he must be able to reach out and touch the base with his hand. If he slides into a fielder while more than an arms length from the base it is interference if he fielder is attempting a play. If a runner goes into a base standing up and this act hindered the fielder in an attempt to make a play, it is interference. If he does not slide, he must get out of the fielder's way.