The project is scheduled to take place over three days.

ARTC group executive for the Hunter Valley network Jonathan Vandervoort said the maintenance program involved about a 1000 workers tackling 122 jobs to help deliver service reliability.

"The work will take place from the port at Kooragang and along the rail corridor to Narrabri, as well as the Ulan line west from Muswellbrook," he explained.

"Similar to other recent maintenance programs, a scheduled 62-hour shutdown is required to allow us to access the track for maintenance and upgrades that cannot be done safely when trains are running.

"The work will start at 6.30am on Tuesday, May 21, and is expected to be completed about 8.30pm on Thursday, May 23."

Motorists in Denman should note that detours will be in place due to the closure of Rosemount Road level crossing on the Ulan line during the three-day maintenance period.

"With upgrades occurring at the level crossing, including improvements to the road approaches and line-marking, road users will need to follow the signage and traffic controllers for detours," Mr Vandervoort said.

"We apologise for the inconvenience and as always we appreciate the patience and cooperation of motorists, commuters and customers right across the maintenance program.

"We also ask people in communities close to the rail corridor to be cautious during the shutdown period and keep an eye out for increased vehicle movements in and out of work sites."

Other works along the network include ballast cleaning, re-railing and track reconditioning.

Enhancements to signalling systems will occur on the Bengalla to Mangoola section on the Ulan line and on the Werris Creek to Burilda section on the main north line, providing increased availability of the network on those lines.

With the shutdown affecting Hunter Valley train services, alternative bus services will be provided, and details and schedules can be found at the Transport for NSW website.