New signs have been urgently installed on a major Sydney road in time for Monday’s evening commute after a disastrous morning on the city’s latest “spaghetti junction”.

It follows a chaotic morning on the city’s new Rozelle interchange, which faced its first test on Monday.

The new WestConnex interchange connects motorists to the M4 and M8 tunnel extensions, the Anzac Bridge, City West Link and the Western Distributor.

Up to 100,000 commuters are expected to navigate its 16.6 kilometres of tunnels daily. It had a smooth opening on Sunday, despite some motorists making a last-minute lane changes an one even switching into reverse on the open highway, as they confronted the new interchange.

But as thousands of peak-hour commuters headed into the city early on Monday, there was chaos for city-bound traffic along Victoria road to Huntleys Point.

“This is a planning disaster, an absolute failure,” one motorist told the ABC after a “nightmare” morning commute.

“My commute will take me an hour-and-a-half and normally it takes me 30 minutes.

“I don’t know where it [the tunnel] goes. It says it goes to Port Botany.

“It’s super confusing, it’s poorly signposted, people are weaving in and out of lanes. I have no idea how this has been so badly planned.”

The confusing signs read “Tunnel City to M8 toll Port Botany” – but did not make it clear there is no toll on the tunnel between the Iron Cove Bridge and the Anzac Bridge. That meant many drivers stayed on Victoria Road rather than bypass traffic along the Iron Cove Link.

Transport officials told the Seven Network Monday morning’s chaos was confined to just one entrance of WestConnex, while the rest of the system ran smoothly.

NSW Premier Chris Minns said the signs had “not been good enough”.

“Many people weren’t aware that you could use a big chunk of that new roadway and not have to pay a toll at all. So, the signing’s got to be better,” he said.

“It will get better, GPS will catch up and they’ll used the learned knowledge of repeat car activity to demonstrate you can use this roadway without having to pay a toll. But I appreciate it hasn’t been good this morning,” he said.

Later, Transport for NSW Coordinator-General Howard Collins said openings of new major roads were always tough, until motorists became familiar with the new set-up.

“Motorists were confused as to what lane they needed to be in as they headed towards the city and this caused heavy traffic to banked up on Victoria Road this morning,” he said.

“To address this, additional variable message signs and extra portable signs were turned on in the lead-up to the tunnel, reminding motorists to use the two right-hand lanes to access the toll-free section of the tunnel between the Iron Cove Bridge and Anzac Bridge.”

“New markings on Victoria Road, leading into the new tunnel, will be put in tonight to make it easier for drivers to know the best lane to be in for those heading to the city.”

Collins said drivers should use the no-toll Iron Cove Link towards the CBD to bypass Victoria Road, between Iron Cove Bridge and the approach to the Anzac Bridge – “allowing motorists to skip seven sets of traffic lights along Victoria Road”.

“We do expect this afternoon to be a busy one also, but we have our Joint Operations Centre stood up, monitoring traffic and ready to respond to any issues or incidents in real-time,” he said.

“Our main concern so far is that we are seeing drivers changing lanes at late notice over the Anzac Bridge heading towards City-West link and Victoria Road – please pay extra attention to road signs, don’t panic, and drive carefully.”

Authorities expect congestion on the interchange may “up to six months to settle down” as drivers became familiar with the network and vehicle GP systems adjust.