It's horrible! I got really frightened cos I thought our train had broken down and perhaps the other train was gonna come up behind and smash into ours! I always think the worst in situations like that though!!!!!!!! x
Hehe - you really should read some more on basic rollercoaster design. The chances you have two trains collapsing on a track really is about non-existing. Basically, the tracks are divided into different sections (each section is usually bordered by either a break section, like on Indiana Jones, where you can easily see where these sections are, or by a lift hill).
A train is only allowed to "enter" the next section if the computer registered that the previous train already left the next section.
You see this happening a lot on Space Moutain; if two trains leave to soon after one another, you sometimes are put on a "break" on the lift hill in the middle of the ride (where you have to get out when it really crashes too LOL).
And before you say computers can't be trusted - don't ever compare a PLC (the chips that work on these things; they also are used in washing machines and ovens - how many times did yours crash?) to a Windows machine

Anyway - just to assure you that the chances really are VERY small...