Rob Mitchell's office is hard to miss.
It's three metres high, four metres in length and it is usually taking up most of the road.
The 28-year-old operates a contract spraying business, which sees him travelling between different farms in Western Australia's Great Southern region.
Mr Mitchell decided to speak up about unsafe overtaking after "one too many near misses". (ABC South West: Kate Forrester)
The size of the sprayer means sticking to the road rules is paramount while travelling between properties.
"If you're over a certain width, you must have an escort in front," he said.
"I have mirrors on either side and have a 180-degree view."
But Mr Mitchell has had one too many near misses recently, even though he believes he is following all the right rules.
He said a growing number of drivers — who are following an unwritten convention on country roads that the driver of a large or slow vehicle will use their right indicator to suggest it is safe to pass — are mistakenly interpreting his right-turn signal as an opportunity to overtake.
"I have indicated to turn right into a paddock and drivers behind me have taken that as a presumption to overtake me," Mr Mitchell said.
"It's nearly caused a T-bone collision."
Mr Mitchell frequently has to move his machinery from farm to farm on main roads. (ABC Great Southern: Mark Bennett)
'My mate's kid was on the school bus'
The most recent near-miss Mr Mitchell had was what prompted him to speak up about the dangers of people using the right indicator as a signal to overtake oversized vehicles.
"A local school bus, which was full of kids, thought I was saying go around me," he said.
"I had to call my mate to say your kid nearly got ran over by me today.
"And when or if it does happen, the headline won't read 'school bus hits boom sprayer', it will be the other way around."
Mr Mitchell says because of the sprayer's size, it is hard to make last-minute manoeuvres. (ABC South West: Kate Forrester)
Assuming a driver's ability
A recent national survey of learner and probationary drivers by the national heavy vehicle regulator found fewer than half of young drivers had been taught how to drive alongside trucks.
Veteran truck driver Glenn 'Yogi' Kendall believes driver ability has declined over his 28 years in the industry.
Glenn Kendall operates a transport business, carting agricultural equipment around Australia. (ABC South West: Kate Forrester)
He said the convention of oversized vehicles "indicating to pass", combined with that lack of ability, was a recipe for disaster.
"The main danger in indicating others around you is 'I don't know your ability', I've never met you before," Mr Kendall said.
"I know truckies do it, but if you have indicated someone around and it put lives at risk, it becomes a real grey area.
"That person behind you could be 80 with no engine power."
Warnings ahead of harvest
Great Southern Police traffic officer-in-charge Derek Grimes has warned drivers that even if they indicated that someone could overtake in good faith, it could create an unsafe manoeuvre.
"If an accident occurs and you have overtaken, irrespective of whether the vehicle in front has indicated you to go around, there is infringements for the person behind," Sergeant Grimes said.
"People in front need to drive to their own capability and allow people to overtake only when it is safe to do so."
Sergeant Derek Grimes says any infringements will always fall on the driver who is overtaking. (ABC Great Southern: Mark Bennett)
Ahead of this year's harvest, Sergeant Grimes also urged drivers to have more patience when driving on country roads.
"Trucks have heavy tons of weight on board with grain at this time of year, they take a long time to slow down," he said.
"Unsafe overtaking offences can go into dangerous, careless or reckless driving and serious fatalities could even occur."