But you have no idea what it is, and therefore have no idea what it's planning process was like. So how can you say 'Portishead's been held up unfairly but road schemes are being pushed through' with any credence at all?
I will also reiterate my point that Portishead is not a trunk railway, but a local connector. Comparisons to Motorways, therefore, are misleading. You want to be comparing Portishead to smaller link roads. I linked upthread to the South Bristol Link Road, providing local people with better access to the existing motorway network - this is far more comparable to the concept of Portishead linking people to Temple Meads.
Is it the Grantham Southern Relief Road?
https://www.lincolnshire.gov.uk/major-projects/grantham-southern-relief-road
The timeline starts in 2007, and opening is estimated for 2025. The 3.5km road is costed at £133m.