A contra-flow was in place at Mount Victoria slowing traffic in both directions but that's now been removed from the highway.

Fires continue to rage in the area, however, with the Gospers Mountain and Grose Valley fires still labelled as 'out of control'.

SUNDAY, 8.30AM: Emergency services are at Mount Victoria battling fires, with a back burning operation on the Great Western Highway impacting traffic flow in the area.

Police are directing traffic through a contra flow, allowing motorists to pass the area in both directions but flow is slow.

Visibility from the mammoth smoke haze is also impacting conditions, and motorists are urged, if they absolutely need to travel through the area, to do so safely.

SATURDAY, 5.30PM: The Great Western Highway has reopened again at Marrangaroo as fire conditions continue to change.

The highway between Katoomba and Hartley has also reopened.

The Grose Valley fire has been downgraded to watch and act, however, another blaze on Upper Turon Road in the Mudgee council area has been upgraded to emergency alert.

UPDATED 4PM: The Great Western Highway is now closed in two locations - eastbound at Marrangaroo, and between Katoomba and Hartley at Jenolan Caves Road. Motorists have been warned there are no diversions and they should stay away.

UPDATED 1.30PM: The Great Western Highway has reopened westbound at Marrangaroo but remains closed eastbound between Reserve Road and Barton Avenue. Live Traffic NSW has advised people to delay travel if they can or drive to the conditions.

The RFS reports the highway at Blackheath is closed in both directions due to the emergency warning at the Grose Valley bushfire in the Blue Mountains - Mount Victoria and Little Hartley residents have been told it is too late to leave.

An emergency warning has also been issued for the Gospers Mountain fire.

Air quality has improved in Orange, but remains hazardous, with the air quality index now at 550 - the index is 767 in Bathurst.

UPDATED 11.30AM: The Great Western Highway is closed again in both directions at Marrangaroo due to bushfire. Motorists are being warned to stay away.

Meanwhile a grass fire at Bulgas Road was extinguished on the roadside at 1am.

Canobolas Zone RFS inspector Nils Waite said it was caught early and only burned through about 400 square metres.

He said the fire was deliberately lit and it was fortunate it occurred during kinder conditions.

"If there was something like that this afternoon, it will turn into a monster," he said.

He urged people not to undertake any activities capable of starting a fire, including grinding, welding or slashing, and to report fires immediately.

UPDATED 10AM: Air quality remains hazardous across Orange this morning due to bushfires to the east.

Readings are third-worst in the state after Sydney's southwest and the Southern Tablelands around Goulburn.

The air quality index was 967, more than four times the hazardous threshold.

Those with respiratory conditions are urged to remain inside as much as possible and follow their health plans in their symptoms change.

7.30AM SATURDAY: The Great Western remains open on Saturday morning but motorists have been asked to reconsider their travel plans today.

A state of emergency remains in place across NSW and with fire conditions expected to worsen throughout the day, police and the RFS have asked people to delay all non-essential travel.

Expected backburning between Lithgow and Mount Victoria did not go ahead last night due to changes in forecast wind conditions.

The fire rating for Bathurst and Central Ranges is listed as extreme today with the Greater Sydney, Illawarra/Shoalhaven and Southern Ranges expecting catastrophic ratings.

The Bells Line of Road remains closed while, to the south of Bathurst, the Jenolan Caves Road and Edith Road are closed between Taralga and Duckmaloi Road and Shooters Hill Road.

Trains are not running between Mount Victoria and Lithgow/Bathurst on the Blue Mountains Line and while replacement buses are running, the buses cannot access the Bell and Zig Zag stations.

More road closures are expected throughout the day.

FRIDAY, 11PM UPDATE: The Great Western Highway is now open in both directions at Marrangaroo, west of Lithgow, after being closed due to a bushfire.

The Traffic Management Centre advises that the speed limit has been reduced to 60 kilometres an hour for eastbound motorists.

The Great Western Highway is also currently open through the Blue Mountains.

Motorists are advised that conditions may change quickly, and roads may close with little or no notice in bushfire-affected areas.

Motorists should exercise caution, follow directions of emergency services, and check the latest traffic conditions at www.livetraffic.com.

FRIDAY, 4:50PM UPDATE: The Great Western Highway is now closed at Marrangaroo, west of Lithgow.

The Traffic Management Centre said the highway was shut in both directions due to a bushfire.

Motorists are advised to avoid the area.

FRIDAY, 4PM:

Orange and the Central West will be cut off from Sydney and the Blue Mountains with the closure of the Great Western Highway on Friday evening.

The road will close from 6pm between Blackheath and Little Hartley for a back-burning operation, cutting off the Central West and metropolitan Sydney.

There's no indication of when the road will reopen.

The Bells Line of Road was closed last Monday and remains that way with the Gospers Mountain blaze out of control.

There is no diversion in place for either closed road.

Motorists are advised to delay all travel though the Blue Mountains, with no access in either direction.

Other roads closed in the area due to the fire include The Darling Causeway between Bell and Mount Victoria, Chifley Road between Bell and Lithgow and Bells Road in Lithgow.

Additionally, trains are not running between Mount Victoria and Lithgow due to the bushfire.

Access between Sydney and the south and the north of the state may also be impacted by fires in the next day so motorists heading away should check before leaving home.

Motorists already in bushfire-affected areas should follow the directions of emergency services and traffic crews and keep in mind that conditions can change quickly and roads can close with little notice.

For the latest traffic information, visit www.livetraffic.com, download the Live Traffic NSW app or call 132 701.

For the latest public transport information, visit www.transportnsw.info or call 131 500.