One question....who's paying for the repairs done on the rails, or tube system, this train is running through and/or on, because at 0.99999998% of lightspeed, the amount of heat generated via friction between the rails and the wheels of the bogies on the train, or it's motion through the transit tube if it's a maglev train, will be enormous!!!!!
Plus the shielding on the train would have to be metres thick and as dense as lead to keep the passengers from being fried by gamma radiation....and extremely high energy gamma rays at that!!!!.