Lithgow City Council mayor Cr Ray Thompson said he was pleased with Thursday's announcement that community input was being sought into the future direction of the Great Western Highway duplication from Katoomba to Lithgow.

"Of course, there have been some for and some against the corridor proposed, but somewhere along the line there had to be a route through," he said.

"They've got to get down the pass some way."

He and deputy mayor Cr Steve Ring were unable to attend the announcement on Thursday due to a prior commitment at Eastern Creek to view waste facilities.

In a letter to the mayor on Thursday, Cr Stephen Lesslie criticised the "disrespect" shown to the council during the announcement.

"Mr Toole announces a major road project but gives such short notice that the Mayor and Deputy Mayor of Lithgow are unable to attend. I was not informed. Were other Lithgow Councillors invited?" he asked.

Bathurst MP Paul Toole told the Lithgow Mercury that the Lithgow City Council mayor was "my very first invitee" on Wednesday morning and that Cr Thompson had been "very apologetic" he was unable to be there.

READ MORE: "Well overdue": Have your say on $2.5b Great Western Highway duplication route | Video

There were considerable restraints in finding a way down into the valley and there were significant challenges in finding the best way around the towns of Blackheath, Medlow Bath and Mt Victoria.

This week, Blue Mountains mayor Cr Mark Greenhill said the plan did not address the needs raised by Mountains residents.

"This looks to me like a recipe to dump more and bigger trucks on to the Great Western Highway, impacting every town from Lapstone to Katoomba," he said.

"I am concerned about the environmental damage this will do, the impact on the world heritage area. I believe that it will make the situation worse for upper mountains towns as well."

The $2.5 billion duplication of the highway was announced by the NSW Government in March this year. It aims to deliver 34km of four lane divided highway between Katoomba and Lithgow, with construction to begin in 2021 and be completed in 2028.

The corridor between Mount Victoria and Lithgow was reserved in local environmental plans in 2013. The NSW Government estimates 23 per cent of affected properties on this route have been acquired. Parts of the existing Great Western Highway that are not upgraded would become part of the local road network.

Between Medlow Bath and Katoomba, the bridges are planned for the highpoints along the ridgeline.

A bypass for Medlow Bath is not on the cards, according to the plan, offering two options north of the village. Further studies will be needed to decide on a final option.

Significant constraints around Blackheath have not been resolved. Options include duplicating the highway through the village centre, the building of an outer bypass with bridges over the rail line to the north. In this option, tunnels would cross the rail line at the south. A third option would include a cut and cover tunnel, a tunnel underpass of the rail line and then a bridge over the rail line to the north, while a fourth option was for a long or short tunnels underneath Blackheath.

You can see more detail online at rms.work/greatwesternhighway or at displays at libraries in Lithgow, Katoomba, Oberon, Bathurst and Orange.

You can call 1800 953 777, email gwhd@rms.nsw.gov.au or write to PO Box 2332, Orange, NSW, 2800.

Information sessions will be held throughout the affected areas. The closest for Hartley and Lithgow residents are: