From The TimeSplitters Wiki

There are many glitches in TSFP Arcade Custom. Many of them include the use of the Buggy vehicle, found in Siberia.

- Blue Base: To get "inside the inside" of the base, you must drive the buggy into the small crevice between the long wall and Blue Base. The vehicle should be stuck in the crevice, continuously attempting to drive by itself into the side of the base. Get out of it and be sure you can step into the wall. Now you are inside the inside of the base, though in a different dimension. Other players can only see your tag above your character. You are virtually invisible!

Cool Tricks Check it out, and you'll see a weapon to the far side of the glitched area. Run to the edge of the glitch and be sure you are aligned with the weapon. Now, run to it! Instead of falling into the abyss of the level, you can make it to the platform and grab the weapon. Now turn left from there, and you'll see the entrance of the base to the far left. Run straight forward until you are adjacent to the entrance. You should not have died, making it across the invisible bridge. Now, turn left and go into the entrance. You have gone back into the "real" dimension of the level. Just look behind you. Now you can see the entrance, along with the inside of the base.

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- Siberia Dam We all get tired of n00bs hogging up the buggy all the time, but theres a way to stop them. First, lade the Buggy with Remote Mines, about 9 to 20 (this works best when planted on the underside of the car or on the side) and aim it at the dam. If you plant enough and aim well, blow it up. It'll fly into sky, either disappearing completely never to fall back to the ice or land on the other side of the dam. Thus, no one will be able to use the Buggy for the remainder of the match.

Grey land This doesn't help you win the game, rather lose it, but it is fun nevertheless. You end up committing suicide in a grey area and seem to fall to your death. This is a pretty tricky glitch. First, get the buggy on the dam, then, with a lot of skill, try to get the buggy to have its back wheels on top of the wall on the back of the dam (the one that has sky behind it). Climb into to the buggy, and if it works, you can get out and fall down this grey area and die.

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- Yellow Base: One can virtually use the same method used at Blue Base here, at Yellow Base. The only difference is that one must get the buggy to climb the rock wall to the left of the base, and step out of the vehicle while it is situated parallel to the base wall. One can basically do the same tricks used in Blue Base, though there is a feature of it that is unique:

The ability to shoot from the other dimension into the "real" , allowing one to kill unaware players. Since the wall of the level is still between the other dimension and the "real", one must take special precaution into coming in contact with it. Since one can shoot from between the dimensions using the wall, and if he/she were to be hit by a stray bullet (or otherwise direct shot from a veteran to the level), the impact would not only inflict heavier than normal damage, but increase the risk of the player flinching enough to pass through, completely, into the real dimension, thus breaking cover and exposing oneself.

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-Get the buggy onto the dam

To do this drive the buggy up the ramp leading to the dam as far as the buggy will go. Get out and plant 6 to 8 Remote Mines on the back of the car. Blow them up and the buggy will launch to the top of the dam where you can drive it around.