Hello Helen
your late train west is useful but if the concert doesn't end until 22:30ish and there's 40-50,000 people trying to get out of the stadium there's no guarantee of catching it. And it's all very well for those who organise events to "encourage" people to use public transport but who pays for it? In Britain most trains and buses are run by PLCs (let's not get started on a political rant over who's fault that is!) and PLCs are legally required to look after their shareholders interests. If the event is something like an FA Cup final then the majority will be travelling from just 2 core centres so it's fairly easy to work out something that won't lose money. But at a concert the crowd comes from all over the place so there's not much that can be done. The problem with Cardiff is that the redevelopment seems to have been done inside out! The stadium should have been at the Bay and the National Assembly, Millenium Centre etc. should be in the centre. Having got that wrong the traffic planners took over and made things worse. I now know all the different ways from Central to Leckwith Rd (better than some of the taxi drivers!) and they all take longer than they should because of the lights, even on a wet Wednesday afternoon! In this case they put the event Park and Ride on the west side of the city when most people came from the east and I bet nothing was done about the lights on Newport Rd.
I've noticed that for some reason the first England-Australia cricket test is being held in Cardiff (presumably the little known English part of the city) in 3 weeks time. That'll be fun! Cricket matches don't have set finish times -the last day may not even happen - so it will be impossible to plan accurately for what to do at the end. In this case it should be possible to run some extra trains without losing money but at what time? What happens if bad light stops play early, or delays it during the afternoon so they play later in the evening? And Sophia Gardens seems even more badly placed for the M4 than the car parks on the east side of the centre.
I like Cardiff, it's one of the better cities in Europe for tourists - just don't go there by car or on an event day!