>>1726907well, it's not difficult to build a barrier. what *is* difficult is ensuring that the barrier positions match the train door positions, and that the software on board the train talks correctly to the barrier ('hey i'm here, open up' 'ok i'm opening up' 'ok i'm opening too'). then, you can only use rolling stock with the doors at those exact same locations and sizes, so you're betting that this is the only door arrangement you need.
PEDs are good and useful - for safety, for comfort (lessening the 'whoosh' of air pushed ahead of the train), and for stopping debris/litter/etc getting blown onto the track - but they're a long-term bet.
