For the inauguration of the main trunk express service in 1909, New Zealand Railways (NZR) introduced new passenger carriages, seating 30 people in first class and 44 in second. These cars featured chairs (three or four abreast depending on class) instead of the old-style bench seats, lavatories in both first and second class, and gangways and gates between carriages. There were also sleeping cars with beds for 20 passengers. By the mid-1920s steam heating was widely used on mainline trains and gas lighting was being superseded by electricity.
In the 1930s better-off travellers could enjoy the trip in luxurious 16-berth sleeping cars or first-class day cars, sheathed in steel panels and lit by electric lights. Writing in the New Zealand Railways Magazine in 1935, Robin Hyde recalled:
Lights out on the Limited – perhaps it's eleven o'clock when the last page is turned and the last yawn yawned. The game then, unless you are travelling by sleeper, is to curl up in such a way that your sleeping-partner can't object, and lapse into the arms of Morpheus.
But for most second-class travellers, travelling the main trunk meant a long, sleepless journey on hard-backed seats, struggling to find 'elusive comfort with the NZR pillow'.
The second-class carriages, which were nearer the front of the train, were also more susceptible to the intrusion of smoke, cinders and coal dust from the locomotive. If windows were left open when the train entered one of the numerous tunnels, carriages were often engulfed in smoke.
In her novel State of Siege (1967), the writer Janet Frame described travelling in a sleeper after the Second World War:
Then followed the dimly-lit, meat-pie journey to Auckland, in a shelf-like top bunk ... Breath soot-high; voices when the train stopped, voices sharp and clear as footsteps walking the platform of the station; steam clouding like cotton wool; heavy-eyed sleep, eyelids sealed with specks of soot. Then early morning, cold clothes with too many arm and feet holes, a fawn railway-coloured, blanket-coloured biscuit; tea; a newspaper. And then, at the end of the jolting, heaving journey ... a slow, measured halting, and in the scatter of people waiting, promising cars and warm homes, crying welcome from Auckland Station.
In 1971, overnight travel between Auckland and Wellington was revolutionised by the arrival of the sleek Silver Star. With its bow tie-wearing stewards, buffet car and on-board alcohol sales, this air-conditioned all-sleeper train offered business and tourist travellers a new level of service and luxury. But increasingly intense air competition saw the Silver Star make its last run in 1979.