Sydney's new tram line from the city to the eastern suburbs is projected to cause more than one fatality a year, according to secret research commissioned by the state government.

A confidential risk assessment obtained by Fairfax Media says the biggest danger from the new line, which will run down George Street and along other busy surface streets, is the possibility trams will hit other trams, cars at intersections, or pedestrians.

The risk assessment by consultancy Arup highlights the number of intersections to be encountered by vehicles on the line to run between Randwick and Kingsford and Circular Quay, and slated to be built over the next four years.

"The risk profile for CSELR [CBD and south east light rail] equates to 1.14 equivalent fatalities per year," says the risk assessment, obtained by Fairfax Media.

Another factor in the analysis by Arup, which was prepared in February and which runs to more than 200 pages, is the speed Sydney's new trams are expected to travel.

According to the study, trams on the new light rail line will pass through 23 traffic intersections at "high speed" (up to 70 km/h), 17 traffic intersections at "medium speed" (up to 40 km/h) and six intersections at low speed (less than 25 km/h).

However the risk analysis prepared by Arup might be somewhat cautious.

The analysis says Sydney's existing light rail line, which runs from Central Station to Dulwich Hill, would be expected to cause one fatality every five years. But there have never been any fatalities on this line.

Asked for a response, a spokeswoman for Transport for NSW said light rail was in general one of the safest modes of transport and, in the case of Sydney, the tram line and general traffic would be widely separated.

The light rail line is also expected to replace hundreds of daily bus services, which are over-represented in casualty figures.

Three pedestrians died after collisions with buses in Sydney's central business district between 2010 and 2014. On George Street, which is where the new tram line is to run, one pedestrian died after being struck by a bus in 2011, while there have also been 20 injuries in the past five years.

Safety concerns about the new light rail line were raised last year after the government revealed trams on the line would be 67 metres long – some of the longest in the world and double the length of the longest tram currently running in Sydney.

The Transport for NSW spokeswoman said the fatality risk quoted was from a "draft version of the report."

"A major communications campaign will happen in the lead up to the opening of light rail, so all road users can take the relatively simple steps that will keep them safe," the spokeswoman said.

"In general, light rail experiences lower injury and crash rates than other transport options including private vehicles."

The Baird government faces a race against time to alert commuters and businesses ahead of major traffic and transport changes in the city when construction of the light rail project begins.

Bus routes from across the city will need to be change.

For instance buses that currently run from Parramatta Road or Anzac Bridge down George Street will soon no longer be able to. The most recent communication from Transport for NSW is that construction should start in September or October.