The trench will be covered by next winter to form a 220m traffic tunnel between the highway and a recon-figured Mountain Rd, enabling buses, taxis and cars to drive over its lid to drop off and pick up rail passengers.
A new bridge is also taking shape beside the Ellerslie-Panmure Highway over the railway to form the start of the busway to Botany and traffic will be diverted to it temporarily from next month to allow the highway's existing road bridge to be replaced.
Auckland Transport major projects manager Rick Walden said the new road, which is expected to carry about 20,000 vehicles daily including 2400 trucks, had to be built first to ease pressure off Panmure's roundabout before that could be replaced.
The ultimate Ameti plan involves taking even more pressure off Panmure by diverting commuter traffic from eastern suburbs such as Howick to the Southeastern Highway via a flyover of Ti Rakau Drive from Reeves Rd behind the Pakuranga town centre.
Subject to funding approval from the Government's Transport Agency, that will be built as part of Ameti's second stage, as will a separate bridge to carry buses across the Tamaki River to Panmure, beside the existing three-lane traffic crossing.
The second stage is expected to cost about $400 million, but the transport bodies have yet to decide whether the Waipuna Bridge needs to be widened to cope with more traffic on the Southeastern Highway, which has a daily count of 60,000 vehicles.
$580m investment in highways
Auckland Eastern Manukau Transport Initiative (Ameti):
Stage 1 (2012-2014)
$180 million. Includes: 1.6km road from Mt Wellington Highway to Morrin Rd; two road bridges; one bus bridge; upgrade of Panmure railway station into bus-train interchange.
Stage 2 (from 2015)
About $400 million. Includes: replacing Panmure roundabout with signalised intersection; busway from Panmure to Pakuranga; separate bus bridge across Tamaki River; road flyover from Reeves Rd, Pakuranga, to Southeastern Highway; 7km of new cycling paths and 6km of footpaths.