(or... Why have the figures been drastically changed ?)
There've been some changes made. Back in 2009, when all the intensive work was being done, consultants Mott MacDonald came up with figures for the likely traffic impacts of the South Bristol Link.
Among all the stats, it was revealed that the road would draw enough traffic onto the new alignment to push up the numbers at both ends. At Brunel Way, as it passes Bower Ashton, another 6,000 vehicles a day would funnel in with the 35,000 that pack it now; along Hengrove Way/Airport Road, there'd be an extra 5,000 on top of the 16,500 that we see today. Frightening, but not really surprising.
Meanwhile, advised Mott MacDonald's experts, the Bus Rapid Transit (sorry, I must learn to call it 'Metrobus') would carry 3,000 people a day along the leg of its journey between Hartcliffe and the A38.
But that was in the olden days. Planning Committees reading the latest reports will find the goal posts have been adjusted and traffic projections rounded right down – and not directly comparable because daily figures aren't given, only the hourly peak and the 'interpeak average'. So on Brunel Way, the new road is now claimed to have no significant effect on traffic levels approaching the Cumberland Basin in the morning rush. Back at Hengrove, the planning committee will be told, morning peak traffic will actually drop (!) once the same road becomes a new ring route through South Bristol.
Just as the traffic numbers are now being played down, it turns out that the SBL Metrobus (you know, the one that's going to be good enough to get people out of their cars) will also carry far less passengers – certainly a tiny number compared with the forecasts on which the scheme was developed. This link (figs 7-12) shows that for most of the running hours, and much of the route, throughout the 15 year study, hourly passenger numbers won't even reach double figures, let alone the 3,000 a day plus on which the whole SBL project was sold.
Conspiracy or cock-up? It needed high passenger figures to justify the scheme in the first place. With that out of the way, and funding secured, low passenger figures can justify dropping the expensive, uneconomic bus element of BRT altogether, leaving just the highway, a new ring road, and a stimulus for developing the Green Belt. Job done.
Of course, I made that last bit up. It couldn't possibly be true. After all, we're going to be European Green Capital.