KEY POINTS:
Auckland's newest railway line has an electric train - but it runs through the belly of the harbour bridge and takes no passengers.
Transit NZ has become a railway operator so it can haul 760 tonnes of reinforcing steel into the bridge's clip-on girders for a $45 million structural strengthening project over the next two and a half years.
It has begun the project by laying 622m of rail tracks inside the bridge's northbound clip-on, and contracted Pakuranga inventor Dave Giles to design and build a battery-operated train for emissions-free haulage through the confined spaces inside the box girders.
The train will take the steel to welders who are due to start work inside the bridge next month.
A second set of tracks will be laid inside the southbound clip-on for similar "stiffening" treatment next year.
Wagons will be loaded with up to a tonne of steel at the northern foot of the bridge, then lifted about 20m by crane to a suspended platform before being lowered on to the train from an overhead monorail.
The 10m train has a driving cab at each end.
Operator Rob Kyle acknowledged from his reclining position high above Waitemata yesterday that it felt "a bit like being in a dentist's chair".
Mr Kyle and his counterpart at the other end of the train have several safety features, including fire extinguishers, back-up batteries and "deadman" controls to stop it in an emergency.
The train has eight driving wheels with a peak output of about 5kw, and will travel at just under 4km/h.
Its batteries harness "regenerative braking" technology similar to that used in petrol-electric hybrid cars, to extend their electrical charge.
Project manager Keith Stolberger said extra ventilation was being installed in the clip-ons for the welders, but the train's operators would have to wear heavy-duty protective clothing while lead paint was removed from the interiors.
Transit will close the northbound clip-on lanes to all traffic for six nights a week from early next month, and throughout the day to trucks weighing 13 tonnes or more.
Its northern operations manager, Joseph Flanagan, said that was to allow welding to take place at night and for steel-work locations to be accurately marked by day without interference from heavy loads passing overhead.
