What You Need to Know About Traffic Volumes
Here's the link to RMS Traffic Volume Viewer shows traffic movements. Clicking on the black shield will show traffic statistics through Blackheath at all times of the day, with am and pm peaks, as well as week days and weekends, westbound and eastbound. The percentage of heavy vehicles can also be seen. All these vehicles must travel the highway between Katoomba and Lapstone. The movements do not show traffic which does not travel beyond Katoomba.
Here's the link from Allianz Insurance. From their research Allianz rank the Great Western Highway between Katoomba and Lapstone No 12 out of the 15 most high risk roads for accidents in Australia. It is the only one in NSW, and has speed limits no higher than 80 km/h. Introducing large B-doubles on to this road would surely increase the risk by a high percentage.
As you can see in the table below, westbound vehicles in the am peak for 2019 already comprise over 25% of vehicle movements through Blackheath, and therefore between Lapstone and Katoomba.
TRAFFIC THROUGH BLACKHEATH (Heavy Vehicle Checking Station - T0298)
This table shows the increase in all traffic from 2015 to 2019 (year not yet complete), with the increased percentage of heavy vehicles on an average daily basis and an average morning peak hour basis (ie approx. 560 heavy vehicles average per a.m. peak).
All these vehicles travel through Mount Victoria, Blackheath and Medlow Bath, and join the existing highway from Katoomba to Lapstone, together with the traffic which originates at Katoomba, or only travels as far as Katoomba.
The Great Western Highway from Lapstone to Katoomba is ranked No 12 out of 15 of the most high risk roads for accidents in Australia (research carried out by Allianz Insurance) and this is with a speed limit of 80 km/h.