Missing your forecast

From today’s Sydney Morning Herald: Cross City Tunnel receivers put tollroad on sale block . The tollroad tunnel went under (so to speak) in part because they missed their forecast, getting 30000 travelers per day instead of 90000.
Another article on this in Toll Roads News The firm responsible for the forecast was Hyder Consulting who remarkably still claim credit for the project on their website.
Forecasting traffic is not easy, but there are established methods that should get freeway demand estimates within 20-30% or better (i.e. one lane) of actual values (not 300% off) and one is not convinced these guys used them. In fact, even with no tolls, traffic was still only 60% of the predicted flow.
Unfortunately, there is really no liability for poor forecasts, at least not for the forecasters.
Of course this points out the advantages to private sector assuming the risk, the public is not on the hook for a bailout. It also argues for higher returns to compensate for the risk, otherwise projects won’t get built.