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Justification for Cambridgeshire Guided Bus is 'built on sand'
CAST.IRON reveals crucial failures in appraisal and modelling
Date Issued: Monday 19th February 2007
Research into archive documents reveals that the Cambridgeshire Guided Bus (CGB) scheme failed some basic tests even before construction began – but the evidence has been ignored.
'It's a complicated business', says Tim Phillips, Chairman of CAST.IRON, 'and that is why it is vital that the scheme is monitored by us at every stage and the public made aware of the truth'.
Documents released last August admit that the 'benefit/cost' ratio for the scheme is now down to 1.968. This is the lowest figure yet conceded by Cambridgeshire County Council, who are the promoters of CGB. The figure originally submitted to government for appraisal was 4.84 when the cost was estimated at £54 million.
The latest cost estimate is £116 million.
That's over 100% increase in costs for 60% decrease in benefits', says Mr Phillips.
The modelling process was subject to a formal, independent audit procedure by the Transport Research Laboratory (TRL), but criticism in that audit has been overlooked. In particular, TRL highlighted flaws in the 'inputs' (which can give huge variations to the outputs, i.e. what will actually happen) and said it was 'abnormal' for non-user benefits – at 66% – to dominate the justification for this type of transport scheme.
Of those non-user benefits, 40% related to road traffic queueing in four specific places.
One of those places is Longstanton, where the new roundabout and by-pass have already neutralised the traffic problems that form part of the CGB cost justification.
The proportion of overall benefits in the CGB scheme for this location works out at £9 million. However, the road scheme already in place was completed for less than £1 million.
The biggest 'queue buster' claim was based on fictitious queue reduction times for traffic at a single, badly timed traffic light at the as-yet-unbuilt Arbury Camps development.
Mr Phillips says that such details undermine the whole case for CGB, as so many of the 'benefits' can be achieved in other ways at a fraction of the cost. 'Many of the benefit claims are dubious at best, particularly the non-user benefits. This may not have seemed important when the benefit/cost claim was nearly 5, but if you strip out the doubtful elements now it is under 2, the ratio drops to 0.656; anything less than 1 is an overall dis-benefit.
'This means that the likely net waste is 35% of the total costs – that's £40 million of public money. The misguided bus scheme was built on sand... and it is beginning to trickle away'.
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