Personally think the route should be extended down to Barry. Adding a few miles of track, 7 stations, maybe the class 153 if that isn't already planned. Always remember being crammed into a 153 on trips down to Barry island in the summer. Could even go as far as Cardiff airport, located just a few miles from Barry. Good a chance as any to add such an extension. I'm assuming the route isn't too far into development as there's not too much information about the route and no screenshots as of yet. So judging from that there's still time
