[[XST]O_x]

pawn Code:

stock GetPlayerSpeed(playerid)
{
    new Float:ST[4];
    if(IsPlayerInAnyVehicle(playerid))
    GetVehicleVelocity(GetPlayerVehicleID(playerid),ST[0],ST[1],ST[2]);
    else GetPlayerVelocity(playerid,ST[0],ST[1],ST[2]);
    ST[3] = floatsqroot(floatpower(floatabs(ST[0]), 2.0) + floatpower(floatabs(ST[1]), 2.0) + floatpower(floatabs(ST[2]), 2.0)) * 179.28625;
    return floatround(ST[3]);
}

pawn Code:

public OnPlayerUpdate(playerid)
{
    if(GetPlayerSpeed > /*your speed limit*/) return Kick(playerid);
    return 1;
}