While technically a high speed ‘regional’ metro(like the ones China has been building) does have a top speed of 160km/h, it is more like regional rail than a ‘lowest tier’ urban transit. Most metro systems have a top speed of 80km/h due to station spacing and physics (motor gear ratios tuned for accelaration).
That or you are talking about the Keisei Skyliner, which is an Airport Express service.
Only send updates of position of the players that are likely to be visible ?