Findings from a traffic investigation will determine whether The Hills Shire Council can implement their preferred outcome of traffic lights at the front of the Castle Hill Day Surgery in McDougall Lane.

The traffic management plan will be conducted by council officers this week enabling the RTA to make a final ruling on the project by the end of the week.

The doctors are outraged by what they have described as ``bully-boy tactics'' from the council who, when approving their building design in 1998, insisted their exit be onto Terminus Street.

``If they can do this to us, I shudder to think what they can do to the average citizen,'' said the day surgery spokesman, Dr John Fox.

``We have been advised by an independent engineer that this option is illegal because it does not comply with Australian building standards but they are going to force it upon us anyway.''

Under the council's proposal, lights will only operate when cars leave the surgery, via the building's one-way internal ramp to the underground car parks. The existing exit from the surgery into Terminus Street will remain closed, after the doctors' own traffic engineers deemed it ``unsafe'', forcing the RTA to put a stop to the project.

The Hills Shire Council general manager, Dave Walker, who is now talking about the project after issuing a blanket media gag last month, said ambulances would have no less facility than what they had now.

``There are traffic light exits like this which work perfectly well around Sydney, namely the Sydney Water headquarters at Parramatta.''

It is understood ratepayers will foot the bill for the $100,000 to $200,000 cost fixing the problem.

The doctors proposal to knock a hole through the wall and exit via the council car parks, also the RTA's preferred option, will not be considered by council because of the commercial impact on the future redevelopment of the neighbouring car parks.