Bristol Numbers
In term of passenger traffic about 20% of passengers at BRS come from South Wales. Whilst that represents a sizeable number they are spread thinly. I often hear a Welsh accent on a BRS flight, but those passengers only represent about 10-20% of the plane. These figures aren't going to sustain stand alone services from Cardiff. In terms of attracting BRS passengers over the bridge I'm afraid that's an uphill struggle. It takes me an hour and a quarter/half to get from North Bristol to CWL, especially if there is traffic is on the roads. If the tunnels are jammed it can take two hours. In an hour and 45 mins I can drive in the opposite direction and reach Heathrow. I've even used London City recently, as since the line was electrified I can travel from Bristol Parkway to Paddington in one hour 10 and use Cross Rail to get to LCY in 30 mins.