This travel time calculation has people talking when Dubbo mayor Mathew Dickerson ignited the conversation recently through his social media.

Back in 2014, Cr Dickerson, a futurist and well-known pubic speaker, made his first case on this proposing a straight railway tunnel crossing from Emu Plains to Mt Lambie covering 70.5 kilometres in his calculation with no speed limit.

In his December 20, 2014 article in another publication he argued "a straight tunnel crossing with a speed limit of 110 kms per hour would result in that distance being covered in a theoretical 38m - and it would be possible to achieve much closer to the speed limit on a multi-lane motorway.

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"This results in a reduction in time of 55m and a reduction in distance of 33.5km. Imagine doing a legal Dubbo to Sydney drive in less than 4 hours! It would open up Bathurst, Orange and Mudgee and practically make Lithgow a suburb of Sydney."

"The logic is still there with petrol price going through the roof, I think most people would be happy to pay $10 toll and save that much on petrol," Cr Dickerson told the Daily Liberal.

"We need this future (longer) tunnel because it would open up this whole region incredibly such as Bathurst, Lithgow, Orange, Dubbo to Narromine and Gilgandra.

"Its hard for me to justify why I am spending my time trying to get the tunnel through the mountains while I've got lots of things to do here but I just want to put it out there so people keen to get these thing going and we hear a variety of thoughts.

"If people are saving on petrol, I think people will be okay with that [paying road toll]."

For his recent argument, Cr Dickerson said he would be reviewing the cost of petrol against his earlier calculation when the average petrol price in Australia between 2014 to 2015 was fluctuating from $1.17 to $1.49 per litre.

The prevailing cost is now astronomical, according to Cr Dickerson comparing his 2014 petrol price calculation that would save an average motorist $1.05 per kilometre.

He recommended $12 per car and $24 per heavy vehicle toll charge on vehicles using the tunnel.

Having more than 30,000 vehicles using the Great Western Highway daily, a quarter are trucks and nearly 48 per cent of them are business travels and freight transport, Cr Dickerson estimated more than $150 million in annual revenue could be generated.

The increased productivity for business would save them $595 million per year.

The current tunnel due for completion in 2024 is part of the $4.5 billion Great Western Highway upgrade between Katoomba and Lithgow.