A quarter of the Waterview Connection twin tunnels are fitted with lights, paving and a system to drop sheets of water to extinguish fires almost immediately.
The 2.4km tunnels, New Zealand's biggest roading project dubbed by some as the "Spaghetti Western", is on track to open early next year.
In the belly of the tunnels, up to 40m below the city, the ceiling is being painted and each bolt pressure tested.
The northern end of the southbound tunnel at Waterview is now fitted out with asphalt, piping and wiring through to underneath the Pak'nSave on New North Rd. Yesterday, the New Zealand Transport Agency and the project's organising group, the Well-Connected Alliance, gave media a tour of the $1.4 billon project.
The ceiling is painted black to suppress drivers' urges to look up as they're moving through, and the panels fitted to the sides by Alice, the tunnel boring machine, as she drilled around the clock, will be white to aide with lighting.
The walls are also marked with morse code-like dots and dashes where the bolts were fitted before the magic of engineering, gravity and physics locked them into place and the fasteners were removed.
Now the tunnels are built, work is focused on fitting out the 2.4km long tunnels - each twice the length of the Auckland Harbour Bridge, so long and curved that the light at the end of the tunnel can't be seen from their middles.
The Transport Agency's Auckland highways manager, Brett Gliddon, said there was still quite a bit to be done and every piece of equipment would be tested before the rubber hits the road next year.
David Taylor, the mechanical and electrical construction manager from the Well-Connected Alliance, said the deluge system is capable of dropping 10mm of water a minute throughout the tunnels, each 30m apart, in case of fire.
"If you're standing on the road during the deluge, you can't see through it," he said.
Other safety features include a PA system to instruct people how to react in any situation, CCTV cameras, vent fans and 16 cross passages so emergency services can cut between the tunnels instead of forcing their way through traffic which could reach up to 2400 vehicles on each of the six lanes every hour.
Mr Taylor said at any given moment, up to 1000 workers are on numerous sites around the project, including welders, brick-layers, fitters and electricians.
When all of the construction and fit-out work is completed, the number of workers will wind down to about 250 as they start testing.
Some of the very last jobs will be laying the tarseal and painting the road markings as emergency services are trained to react to situations in Waterview's belly, and a huge public information campaign is rolled out to teach motorists how to drive in tunnels - changing lanes in the Waterview Connection will be a very high-risk manoeuvre and trucks carrying dangerous goods will be not be allowed through.
When the Waterview Connection opens early next year, it will complete the Western Ring Route, a new 48km route to the west of Auckland, connecting Manukau, the city, Waitakere and the North Shore.
Cost: $1.4 billion
Started: January 2012
Estimated completion: Early 2017
What it involves:
• 4.8km link for three lanes of traffic each way between the Southwestern and Northwestern Motorways, 2.4km of which will be through twin tunnels.
• Three-deck motorway-to-motorway interchange at Waterview, with four ramps of a combined length of 1.7km, the highest of which is 23m above the ground.
• Compacting 74,500m3 of aggregate for backfill.
• Laying almost 5km of drainage pipes.
• Installing 104 flame traps.
• 140,000m2 of paint - black for the roof, white for walls.
• 4000 lights and 62 ventilation fans.
• 50km of cable trays to support wiring and equipment.
• 400km or 270 tonnes of cabling and wiring.
• CCTV cameras and signage.
• 5 deluge storage tanks for fire control.