What measures do railway cars use to avoid collision?

Question

I have often wondered how 2 trains avoid traveling on the same rail avoid colliding with each other. How do the appraoching trains, accidentally traveling on the same rail avoid this collision? With the frequent use of the railroad, why aren't there a higher occurence rate of collision?

Answer 1

trains use a device called a collision whistle. Warning the operators of the impending collision.

Answer 2

Electronic sensors and Brakes.