It’s 7.40am on Monday morning and Stiofan Sexton is about to do something he has never done before – and he doesn’t even know it.

Waiting on the platform at Sydney’s Chatswood station, he is one of the first thousand passengers on the new fully driverless Metro Northwest in its first weekday rush-hour test.

He used to take a slow bus up to work in North Ryde. Now he steps on to a carriage that goes up to 100km/h, along a 66km track, with service every four minutes, all run by a single computer.

Asked by Guardian Australia how he feels about the fully automated train, he says he did not realise it was.

“I didn’t know that,” he says. “It’s my first time on it. So it’s fully driverless is it? Unreal. It excites me. That’s what it’s all about really.”

On Sunday, travel was free, and packed with trainspotters. Complications struck – the metro overshot platforms and had to slowly wriggle back and forth. Doors didn’t open. Today, it is smoother and quicker.

On the Chatswood to Tallawong line, a steady stream of passengers queue at the front. Through a glass window you can see the driverless metro eating up the tracks. A father is videocalling his children and shows them the view.

Back at Chatswood, on the opposite platform, Mazhar Jafri steps off, beaming.

He works where the metro ends and used to live 20 minutes away by train, in Waitara. Last week he moved further, to Castle Hill, but his commute is the same.

“The train was on time, it was very clean and everything,” he says. “Today was the first day I caught the train from Castle Hill station. It was 20 minutes from Waitara, now it’s 20 minutes from Castle Hill – either way it was very convenient. I’m very happy to be part of the journey.”

Susan Yu also steps off at Chatswood, early to work. It is her second time on the metro and it saves her half an hour each way – but she wants one key change.

“The train was pretty fast but the seating – I’m still used to the old seating,” she says. “It was more comfortable. This was very hard. When the train moves, everybody and bodies just move. You bump into each other.”

She doesn’t mind the automation (“Mentally it was scary but, when you ride on it, it’s OK”) but misses the standard double-decker seating of Sydney trains.

“I wish they could change it to the normal carriage,” she says. “It would be a lot better. I know it’s a short trip but it’s still 25 minutes for me on the train.”

For Sexton, his first trip is all positives.

At Chatswood, everybody stepped on, clearly gawking, but trying to hide it. A very ambitious man brought his bike on – it gets stuck in the door – but with a quick push he is in.

On the map, a display bar shows you, in moving increments, how far from each stop you are.

But there are still teething issues. An overly anxious warning system won’t stop telling passengers to stay clear of the doors – and loudly repeats this for a good few stops. People start whispering complaints. The progress bar stops working, frozen at North Ryde.

But it sorts itself out. Transport NSW says it tested the driverless trains over more than 180,000km – roughly 4.5 times the length of a trip around the equator (40,000km).

After 10 minutes, Sexton is at his stop.

“It’s good,” he says. “It’s fast, faster than I thought. It’s smooth, it’s quite nice.”

He points to the track.

“It’ll definitely shave off a few minutes for me. If I go in a bit later on the bus, I get stuck in traffic. Here, I can get it any time.”