The bendy buses are being mooted as a solution to expanding passenger capacity through the Karori Tunnel – which is not tall enough to safely fit double decker buses.

Other options, such as daylighting the tunnel and building a viaduct for Raroa Rd, had been disqualified due to the prohibitive cost.

The vehicle, which can seat 67 and has a standing capacity of 47, will follow the route to gauge any obstacles.

About 10,000 people travelled the route each day, Nash said –three million trips over the past year.

Sensors had been attached to the vehicle to see where the bus would track on Wellington’s roads, Nash said.

He estimated about 40 to 50 car parks may be removed along the 2’s route due to the need to extend bus stops to accommodate the extra length of the buses.

“We will be working with Wellington City Council to work out what needs to change – the layout on the road, traffic furniture, or car parks.”

The diesel-powered bendy bus is an Auckland Transport bus used for school runs, Nash said.

Nash said procuring electric versions would mean a difference in price with modern electric articulated buses costing around $1.4 million to purchase.

The bus has a turning circle of 24 metres, and requires a Class 4 licence to drive – the same as that for the double decker buses.

Advantages included faster loading of passengers and improved mobility access, but they took up more space at bus stops.

The trial is designed to help Metlink understand the possible constraints through the narrow streets of Wellington’s hillside suburbs.

It will also allow Metlink officers to check the accuracy of the expected path of the bus against the actual path on the route.

The trial will be run late in the evenings to avoid disrupting timetabled services and traffic flow. Passengers will not be able to board the bus.

A possible purchase decision will be made in mid-2024, if route infrastructure is in place for the buses from 2026.