The NSW government has warned that Sydney's bus network still faces several "tough weeks", despite passing the first test of major changes to timetables and routes.

While the network operated relatively smoothly on Tuesday, Transport Minister Andrew Constance said the city had a "long way to go" before commuters adjusted to the changes. George Street, a major arterial route in the CBD, has been closed to buses to allow for construction of a light-rail line.

"We have got a tough couple of weeks ahead," Mr Constance said. "It is going to take a good number of weeks for people to settle into the rhythm of the city as a result of us taking buses out of George Street and completely overhauling the network. One good peak hour this morning doesn't mean we have bedded this in."

Premier Mike Baird dismissed suggestions the government had overstated the impact of the changes to commuting times and congestion on roads in the CBD.

"This is an unprecedented change. People are being inconvenienced but obviously what we are trying to do is minimise it," he said.

The majority of commuters canvassed by Fairfax Media on multiple bus routes into the city were either pleased or nonplussed about the changes.

"I think it was better than normal," Elise Smith, of Neutral Bay, said. "It flew straight in. I say keep it this way."

However, some commuters faced delays during the afternoon peak due to congestion from buses driving from York to Druitt streets, and then onto Clarence Street near the Queen Victoria Building.

Passengers also highlighted long delays to bus journeys on Castlereagh Street.

Transport officials again urged commuters to plan their trips. Traditionally, traffic is lighter on the first day after a public holiday.

While avoiding any major congestion on Tuesday, transport authorities still had to deal with a bus with a flat tyre at Wynyard, an accident in the Harbour Tunnel and a truck that hit a sprinkler system in the airport tunnel. It was the second time in four months that a truck has disrupted traffic in the tunnel.

CBD transport co-ordinator general Marg Prendergast also warned that Wednesday would be a bigger challenge because of higher levels of road traffic. "We think [Wednesday] will be the real test," she said, urging commuters to try to avoid travelling during the morning and afternoon peaks.

"One message for commuters is update your apps. There are people who are using the trip planning off the apps who might be on the old timetable."

The first closure of George Street to cars will occur on October 23 when a section between Market and Park streets is cordoned off for construction of the light rail line.

After a number of people narrowly avoided being hit by vehicles on Tuesday morning, Ms Prendergast warned pedestrians against jaywalking on George Street near work sites.

Despite the new bus system passing its first test, NSW Labor leader Luke Foley again warned that congestion in the CBD would get worse when construction of the light rail line ramps up.

"This isn't about one morning. This is about the weeks, months and years ahead. To be building a light rail line system down the central north-south spine of the city is the wrong transport project for the CBD," he said on Tuesday. "You can't be for the motorist and be for light rail down a narrow George Street – the two don't go together."

Unlike Melbourne, he said Sydney streets were not wide enough for city trams.

Labor transport spokesman Ryan Park said commuters were picking up the tab for the project. "It is not fair that commuters have to be forced off one public transport mode, get on another, and for the privilege, they have to either pay more or walk more," he said.

But Mr Constance said commuters would not need to pay twice if they simply changed buses.

"Bus-to-bus interchange is one fare, and in terms of bus-to-train ... people still have the option to get onto a bus and do the bus interchange," he said.

The state's pricing regulator is conducting a review into integrated fares, and is due to release a draft report in December.

An issue also might be emerging with buses from the Hills District, which are now being directed to the Western Distributor, and back north through the city via Bathurst and Kent streets.

But this route means those buses, servicing suburbs such as Dural, Cherrybrook and West Pennant Hills, no longer travel on the dedicated bus lane on the Harbour Bridge.

One commuter, Matt, said his journey time to work almost doubled on Tuesday. "The bulk of the delay was actually just being stuck in the general traffic across the bridge," he said.