First, the RTA's own projections are used in modelling traffic impacts and are therefore critical in deciding what road changes would be required. The fewer cars there are using the tunnel, the more will still be using the surface roads. So if the RTA's tunnel projections are too optimistic, and the road changes have gone ahead on this basis, there is a risk of congestion remaining on the surface roads.
Second, if CCM does not achieve its optimistic projections, its financial viability would be at risk. Under a worst case scenario the Government might need to step in to keep the tunnel open amid potentially significant traffic disruption. Also, CCM's projections influenced the RTA's revised projections for the 'Long 80' tunnel.
These are significant risks. We consider that there should have been more rigorous evaluation of the patronage projections, including those commissioned by the RTA. We discuss the impact of the patronage projections further in Chapter 4.