[Lordzy]

You could use the SetTimer function at OnGameModeInit() and when the timer ends, set player's position to some other place(I haven't done derby before).

Example:

pawn Code:

public OnGameModeInit()
{
 SetTimer("MapChange",900000,false); //We've set a 15 minute timer.
 return 1;
}

forward MapChange();

public MapChange() //After 15 mins.
{
 for(new i; i< MAX_PLAYERS; i++) //Looping through players.
 {
  if(IsPlayerConnected(i)) //After looping, we're choosing connected players.
  {
   SetPlayerPos(i,yourposX,yourposY,yourposZ); //Setting all the connected player's position. You've to set the pos.
  }
 }
 return 1;
}
//Just an example.

.