Clem 7 traffic estimates predict 50,000 car shortfall

The Clem 7 tunnel will carry 54,000 fewer vehicles a day than its builders anticipate by 2026, according to traffic estimates provided as part of the building of the Northern Link tunnel.

If true, this would a mean shortfall in tolls collected of more than $200,000 a day, or $6 million a month.

The Clem 7 tunnel will connect Woolloongabba to Bowen Hills.Credit: Michelle Smith

In 2006, RiverCity Motorway won a 45-year concession to build and run the Clem 7, Brisbane's first road tunnel project, which will run from Bowen Hills to Woolloongabba and is due to open in mid-2010.

Its traffic estimates, provided by private toll company Maunsells, predict an average of 136,188 vehicles each day using the tunnel by 2026.

However, traffic estimates completed by Sinclair Knight Merz and Connell Wagner in June as part of Brisbane City Council's Northern Link tunnel predict only 82,000 vehicles will use the Clem 7 tunnel by 2026.

That is 54,188 fewer vehicles on average each day.

Both companies say they have factored in the impact of the Northern Link tunnel, which runs from Toowong to Bowen Hills, and say it impossible to compare the estimates because "assumptions" for both are different.

But RiverCity Motorway's own financial statements point out the effects differing traffic projections could have on the $2.8 billion Clem 7 tunnel's financial base.

"If traffic assumptions over the entire concession period differed to estimates by +/-5% then the value in use would be impacted by +/- $99 million," its 2009 financial statement states.

The Connell Wagner/Sinclair Knight Merz traffic prediction is 40 per cent lower than RiverCity Motorway's.

Two Sydney tunnels have had troubled histories based on traffic projections that were never reached.

Sydney's Lane Cove tunnel, run by Connector Motorways, originally projected 100,000 vehicles a day by September 2007, but was struggling at 62,364 in February 2008.

By September this year 73,761 vehicles a day were using the tunnel plus the Military Road ramps.

A second Sydney tunnel, Sydney's Cross City Tunnel, was placed in the hands of receivers in April 2007 after projecting 90,000 vehicles a day, but carrying only 30,000.

Maunsell defended its traffic forecasts, saying it had sound forecasts on other tollway projects, such as Melbourne CityLink, and the M2 and WestLink M7 in Sydney.

A spokesman for Brisbane City Council described the Sinclair Knight Merz and Connell Wagner figures as "conservative", and the Maunsells figures as "aggressive".

Maunsells defended its 2006 modelling, describing it as "extremely detailed".

"It is important to note that these forecasts take into account future road network changes, including the opening of the Northern Link tunnel," a spokesman said.

"This forecast was prepared following extensive data collection, modelling of the transport network, consideration of potential network changes, existing and projected population and employment growth, planned urban development, assessment of people's willingness to pay tolls and other economic factors.

"It was a very in-depth study, focussing particularly on the Clem 7."

Brisbane City Council says the estimates by Sinclair Knight Merz and Connell Wagner for the Clem 7 tunnel project were completed in February 2005.

It includes estimates "with" and "without" Northern Link.

RiverCity Motorway refused to comment on the opposing figures when contacted by brisbantimes.com.au.

"RiverCity Motorway is not in a position to comment on the traffic forecasts prepared for the Northern Link EIS process and have no specific detail of the modelling undertaken," it said in a statement.

"Questions regarding Northern Link modelling should be referred to Brisbane City Council."

Brisbane City Council said its estimates for Clem 7 did include traffic projections, but was not as broad-based as the work completed by Maunsells.

The wide variation in the traffic modelling is apparent even earlier in the modelling.

By 2016 Maunsells estimates that 116,384 vehicles each day will use the Clem 7 tunnel, while the Sinclair Knight Merz Northern Link project team estimate 65,900 by 2014, growing at about 1350 vehicles a year.