Frank Black is back on the road after two weeks out of work when he spots a sign, a little too far from where he’s standing to make out clearly.“Is that $2.08 for diesel?” he says. “I’ve gotta check that price out. If that’s right I’m gonna fill up!”It’s not. Diesel hasn’t been that close to $2 since before the war in Iran. Black won’t be filling up here. He climbs back into his truck, rumbles it to life and continues on his journey.The 40-year-old trucking veteran has been caught up in the global fuel crisis triggered by the war. Like other truck drivers, he relies on diesel – and lots of it. Prices rose from about $1.80 a litre to a peak of about $3.20 in April.As an owner-driver, Black goes by the rule of thumb that one-third of a job’s pay should go to fuel, one-third to truck maintenance and the remaining third to wages.But when diesel prices surged, the numbers stopped adding up, forcing him to “park’ his truck for more than two weeks – it just wasn’t worth going to work.Even without a fuel crisis, “we work on slim margins anyway”, Black says, “so the slightest volatility in fuel or any costs is going to put pressure on small operators”.The war in Iran has been “the final nail in the coffin for a lot of people”.‘The house is on the line’Black is on his third week on the road. After carting mining equipment through the outback from South Australia to Queensland, he made his way down the east coast, picking up jobs as he went. I join him as he drives north again from Sydney to Brisbane, a truckload of stage equipment in tow.Filling up with diesel on the road to Brisbane. Photograph: Sarah Smaje/The Guardian“After that, I’ll see what happens,” Black says. “It’s part of the deal being an owner-driver like I am … I go everywhere and anywhere.”The sun fades and the lights of passing cars and trucks rush by as we tumble down the two-lane highway towards Narrabri in northern New South Wales. The radio crackles as we pass out of range of a local station.