If the Basin Reserve flyover goes ahead as planned it could cause more crashes in central Wellington, independent traffic experts have warned.
With the flyover's four-month board of inquiry hearing almost at an end, the board has heard from its own independently-commissioned experts about the concerns they still have for the $90 million project.
Helen Andrews, the board's legal counsel, said Abley Transportation Consultants were worried about the situation motorists would face when they moved off the proposed westbound flyover, 20 metres north of the Basin, and entered the Buckle St underpass.
Once the flyover is built, the New Zealand Transport Agency proposes to give motorists the option of turning left into Taranaki St after exiting the underpass, rather than forcing them to continue straight along the Inner City Bypass (Karo Drive).
Doing so would encourage more motorists to change lanes inside the underpass, as they try to make their way across to the left-hand side, Andrews told the board.
"This additional weaving would substantially increase the number of potential conflicts within the underpass and inevitably lead to more crashes."
Allowing the left-hand turn could also delay some of the State Highway 1 traffic wanting to travel west, she said.
No one knows how big the delay could be because the transport agency has not had time to model the scenario.
In documents presented to the board, the flyover's project manager Selwyn Blackmore said the left-hand turn was a relatively recent design change requested by the Ministry of Culture and Heritage to discourage motorists from using a road through the soon-to-be-constructed National War Memorial Park, above the underpass, to access Taranaki St.
If approved, it would mean the road through the park would only be used for vehicles needing to access local properties, such as Massey University.
But Mr Blackmore said the board need not worry about the issue because the final design of the underpass lanes would need approval from both the Wellington city and regional councils.
Andrews said the traffic experts at Abley were also concerned about the proposed 3-metre wide cycle and pedestrian path that will run along the flyover's northern edge.
Given cyclists would be travelling a lot faster than pedestrians, the narrow width of the path was a safety issue, she said.
Abley believed the shared path should be a minimum width of 4.5m. It also suggested including a 1.2m-high handrail where the path adjoins the flyover to minimise the risk of cyclists toppling over the safety barrier into traffic.
The transport agency says its approved safety guidelines allowing for a 3m-wide path, and making it any wider would place it extremely close to St Joseph's Church.
The agency will sum up its case for approving the flyover's resource consent this afternoon.
- The Dominion Post