Marble Bar Road

depends on if it has been hit by cyclones at all which is a 50/50 bet. Will be closed if it has been raining

cyclones will wash out the creek crossings making them rough.
generally a good road we were restricted to 90 on it and it pays to keep the speed down as although generally good those creek crossing rush up on you.
this road will have seen a huge increase of traffick since i last drove it just over a year ago so could be carragated now with all the road trains with mines starting up along it.
Used to take about 2 hours from Nullagine to Newman

Temperatures average in the mid to high 40s in January, so you'd want to make sure you have a reliable vehicle, plenty of water and be well prepared. Overseas tourists regulary die in Australia from dehyradtion after becoming stranded in the hot conditions. Without water in these sort of temperatures, people don't often live past 1 day.

January temperatures for Marble Bar

While I don't discount what you're saying, the temperature/rainfall graphs give a pretty good indication on what to expect.

Andrew...........am up around that way allot .cutting through from mine site to site........the roads ok .another dirt road ...dont compare it to bitumen....so adjust to the conditions....all in all its a fair run..marble bar to Nullagine..and down to the cloud break mine.turn...is always better than the section from there to Newman....as loads of trucks and haul trucks running at full noise .......so beware from there in nice drive with lunch break.3.5 hours
cheers Bundy