As well as relieving acute traffic congestion in the city, the finished road will bring environmental benefits, better air quality and create the 'central and final link' between the M32 motorway and A4 trunk road.
David Holgate QC, for the department of transport, was urging three appeal court judges to dismiss the challenge to the road scheme brought by railway enthusiasts, Barry McNeeney and Andrew Nicolson.
The pair, both from Bath, are desperate to save an 850-metre stretch of the historic Bath and Bristol Railway Path - as well as a large swathe of Siston Common - from disappearing under the new road.
Like the M25 motorway around London, Mr Corner raised the spectre of the Avon Ring Road 'entering folklore as a victim of its own success,' by actually increasing the traffic congestion it was designed to do away with.
But Mr Holgate insisted today that the road represented 'good value for money', effectively meeting overwhelming public demand.
'There are currently heavy traffic flows on unsuitable roads in residential areas adjoining the scheme which will be greatly relieved. The scheme would enable environmental improvements to go ahead,' he told the court.
When complete, the ring road would form an 'essential part of the National Primary Road Network', greatly improving south Bristol's access to the motorway network. Residential areas would be bypassed resulting in improvements in road safety and air quality.
Mr Holgate said that with the ring road incomplete, the advantages of the finished sections of the road, built at the cost of millions to the public purse, could not be realised.
The future of the multi-million pound Emersons Green development - designed to create housing and employment land to last Bristol into the next century - would also be placed in jeopardy if the missing link is not built.
He added: 'There would be improvements achieved for ecological interests, noise levels and air quality. Traffic pressure on urban and rural areas would be significantly relieved.
'The total benefits of the ring road cannot be achieved unless it is completed.' Mr Holgate said the department of transport had 'clearly taken into account' concerns from anti-road pressure group SCRAPPIT that the road would create high levels of 'induced traffic', actually increasing traffic congestion.
'The secretary of state did take the induced traffic argument into account and therefore cannot be criticised.
'He has chosen to give very much greater weight to the wide, overall, benefits of the scheme.'
Mr Holgate ackowledged that the government's COBA computer which had projected that the road would be of 'distinct economic value', had not taken account of the induced traffic threat.
But he told the court the computer had also not taken full account of the social, environmental and economic benefits of the scheme
Earlier today the case took a dramatic turn when it was revealed that one of the appeal judges, Lady Justice Butler-Sloss, is chancellor of the University of the West of England which has an interest in the development of a science park at Emerson's Green.
The judge said she had had no idea of any connection between the university and the development, and Mr McNeeney and Mr Nicolson made no objection to her continuing to hear the case.
The hearing continues and the court made up of Lady Justice Butler-Sloss and Lords Justices Aldous and Auld, is expected to reserve its decision to be given at a later date.