The NSW Government has been warned that overcrowding at three Sydney train stations could become so bad that commuters are at risk of being "crammed in like sardines" in environments "conducive to panic".

After a legal battle, ABC News can reveal consultants' reports which detailed unacceptable and sometimes dangerous overcrowding risks at Epping, Strathfield and North Sydney stations.

The reports, prepared by the Beca consulting firm in 2015, use coloured heat maps to outline the number of pedestrians using future timetables from 2018 and 2024.

Some maps showed large zones of red, representing a safety standard of LOS F (Level of Service F), which means crowding of 10 people or more per square metre.

At that rating, free movement could become impossible and queues dangerous.

One report described the rating as "people crammed in like sardines", with an "environment conducive to panic in large crowds".

By comparison, the highest level, LOS A, is less than one person per square metre.

Nirajan Shiwakoti, an urban transportation expert in the engineering faculty at RMIT, said the maps suggested major safety problems.

"What we have seen in previous disasters is they are likely to occur when the flow of people exceeds capacity," Dr Shiwakoti said.

"At Level of Service F the flow is unpredictable – if one person pushes another person, that is dangerous and can cause a chain reaction, and a dangerous, unpredictable situation."

Crowd crush risk at Epping

Epping is a station facing significant congestion in 2024 when platforms five and six will operate as a transfer point for commuters on the new Metro line from Castle Hill.

Report authors warned in some scenarios elevators and the concourse could become congested at the Level of LOS F, due to the larger number of pedestrians switching platforms.

The report warns: "This could cause a situation where those arriving at the top of the escalators from platforms five and six will have nowhere to go."

"This could cause a crowd crush situation."

During the morning peak, large areas of unacceptable F rating have also been mapped on Epping's platform one.

The authors suggest the elevators are a "problematic pinch-point" and point to "poor platform clearance times" causing impacts to the on-time running of trains.

Consultants heat-map modelling shows red areas of dangerous overcrowding on escalators and on the main concourse at Epping in a 2024 peak-hour scenario. ( Supplied )

Bottlenecks at North Sydney

North Sydney is described as the fifth busiest station in Sydney, and the report said the station had already encountered overcrowding during peak hours, especially in stairwells, lifts and escalators, creating congestion on platforms.

By 2024, some peak-hour scenarios, such as a cancelled train, could create major congestion worries especially on main platform four.

With the platform so heavily constrained, movement could be blocked for people trying to exit the station.

The crowding would also affect the upper concourse, as escalators and elevators used by pedestrians became bottlenecked.

A 2024 cancelled train scenario reveals major areas of unsafe overcrowding (in red) on North Sydney's platforms three and four. ( Supplied )

Insufficient gates at Strathfield

Strathfield is a busy station in both afternoon and morning peak periods, and the report said by 2024, its two gate-lines face unacceptably deep queues — up to 10 people deep — blocking pedestrian access to western ramps, and heavily constraining entry and exit to Strathfield Square.

Dr Shiwakoti, said the heat map suggested two crowds coming together in conflicted movements, could create narrow bottlenecks, which could be dangerous.

"We can see in the concourse, two flows merge together. Our recent research demonstrates that stampedes can happen at T-junctions like this - such as in 2010 in Germany's Love Parade event disaster, this was caused by merging sections of crowd where many people were killed," he said.

Major infrastructure upgrades not the only solution

The consultants recommended infrastructure upgrades as a solution to overcrowding with improved gateways needed at all three stations.

Several train stations are at risk of LOS F - a fail rating for crowd safety. ( Supplied )

In North Sydney, additional suggestions were to remove buildings and structures from the platforms and replace stairs with high-speed elevators.

The consultants acknowledged this might require the station to close to the public for a long period for major construction.

In Epping, it was suggested extra elevators and escalators be installed, but it also acknowledged that space and design constraints might not allow this.

Another suggestion to planners was to consider encouraging Metro passengers to transfer at other stops, such as Chatswood station.

The ABC also received reports on Parramatta and Hornsby stations, which, while performing better, might also require infrastructure upgrades in the future.

Requested pedestrian modelling for Town Hall, Chatswood and Central stations have not yet been provided by Transport for NSW.

A departmental spokesperson for the Transport Department said safety was its first priority in future plans.

"Capacity, customer comfort and the reliability of trains are other important factors that we consider," a statement read.

"Work to finalise future train timetables continues."

In a radio interview, Transport Minister Andrew Constance criticised the ABC for reporting on three-year-old planning documents.

However, the concept documents were obtained less than two weeks ago after a ruling by the NCAT found in the ABC's favour for release under public interest considerations.