Trams will begin running every four to six minutes through the heart of Sydney within two weeks to simulate the $2.7 billion light rail line's timetable ahead of passenger services starting in December, prompting transport officials to warn people to be extra vigilant.

The government has also decided to delay major changes to bus services in Sydney's south-east until April, about four to six weeks after a branch of the light rail line to Kingsford opens.

A pedestrian crosses in front of a tram on George Street last week. Credit:Janie Barrett

Driver training is taking place using more than a dozen trams along the line from Randwick to Circular Quay, which is due to open to passengers in early December.

Transport for NSW's coordinator general Marg Prendergast said testing had shown there had been an increase in cases of poor pedestrian behaviour and vehicles blocking intersections as more of the 67-metre long tram sets ran along the line.