There are a couple of ways to game a speed limiter, a mandatory device fitted to heavy vehicles to control how fast they go. A lot of people in the industry know how to do it, and a lot of people know how widely it is done.
When NSW police raided Lennons Transport on Wednesday an Assistant Commissioner, John Hartley, said the operation was unprecedented.
Launching Operation Marshall, officers swept through the company's Enfield headquarters. They intercepted trucks across the state. Drivers for Lennons, tipped off about what was happening, abandoned their vehicles at Casula and by the side of a road in Victoria.
But what the police found - widespread evidence the company was rorting speed and safety regulations - came as small surprise to many with a close knowledge of long-haul trucking.
The industry, report after report has described, survives on testing the limits. It tests the limits of the people who work in it, and they test the limits of the law.
One way they do so is to manipulate speed limiters with ''whizzers'' - a device about the size of a cigarette packet. The whizzer can be fitted anywhere in the truck's rig, and it plays with its electronic timing.
''It sort of pumps electronic impulses through the electrical wiring which speeds up the timing of a truck,'' says Euan Scott-Bell, a company driver for Toll, who has not used whizzers but has just been told about them.
''The truck then always seemed to be starving of fuel,'' Scott-Bell says.
The truck's computer thinks the truck is travelling one speed. But the whizzer dupes the engine into receiving more fuel and then running faster.
Another method involves fiddling with the truck's gearing ratio.
"They put a ring around the gear box off the drive line,'' says another driver, 60, and with 38 years experience.
This driver, who does not want to be named, explains this method involves changing the number of ''teeth'' or sensor points attached to that ring.
A ring with "12 sensor points" might tell the truck's computer it has a top speed of 100km/h, he says, but a ring with a different number of sensor points "tells the computer we're right for 130ks''.
Both drivers, Scott-Bell and the anonymous veteran, say they have not tampered with their speed limiters, nor do they now. But this is what drivers are talking about this week.
''The industry's alive with rumours and stories today,'' Scott-Bell said on Thursday. ''They are obviously not the only ones doing it.''
Lennon's was the employer of Vincent George, who crossed to the wrong side of the Hume Highway in his B-double last month and hit and killed Calvyn Logan and his parents Donald and Patricia Logan.
It was this tragedy, on January 24, that triggered Operation Marshall and the week's dramatic events.
When police charged Mr George they alleged speed was a factor in the accident. If it was not, it was definitely a factor a day earlier when Mr George was booked at Wagga Wagga travelling 133km/h, more than 30km/h above his speed limit.
As anyone who drives the state's highways knows, trucks regularly travel above their 100km/h speed limit.
This should not really be possible. Since 1991 truck operators have been required to fit speed limiters.
The limiters control the ability of a truck's engine to propel the vehicle beyond 100km/h. Trucks can still go faster than this, and easily, but only legally if they are going downhill.
Yet you don't need a whistleblower to know speed limiters are regularly tampered with. In 2007, the National Transport Commission estimated that tampering with speed-limited heavy vehicles was in the range of 10 to 30 per cent. The Transport Commission thought for some heavy vehicle classes the rate could be even higher.
On these numbers, and given there are over 120,000 heavy vehicles in NSW, there could be more than 30,000 trucks with tampered speed limiters in the state.
Before this week, however, the police have struggled to fine or prosecute companies or drivers.
Figures provided to the Herald showed that between January 2010 and August 2011, Roads and Maritime Services sent out 365 ''directive to check heavy vehicle speed limiter'' notices.
As a result of these notices, they suspended five vehicles.
Soames Job, the former director of road safety for Roads and Maritime Services, has some sympathy with law enforcement on the issue. ''The enforcement difficulty is actually finding the bloody things,'' he says of whizzers.
''I thing that's a huge problem. So while there's been knowledge of it, to actually prove it is incredibly hard,'' he says.
Scott-Bell, the Toll employee, is a rare driver relatively happy with his lot. He is a delegate to the Transport Workers Union, he works for a major operator, and is on a regular salary.
''I'm lucky, mate, I'm a company driver, I get paid hourly for everything I do: I get paid waiting, get paid waiting for paperwork,'' he says.
''Whereas the majority of these interstaters - they don't, they just get paid from going A to B.''
Many of the reports into the trucking industry highlight this remuneration structure as a major cause of unsafe driving practices. The majority of drivers either work for themselves or work for very small companies.
The most recent survey of the industry, by the Bureau of Industry Transport and Regional Economics in 2003, reported 85 per cent of the industry worked for firms with fewer than five employees.
These smaller firms, in turn, often work on contract to larger companies. Lennons, for instance, the subject of this week's raids, would work on contract for the trucking giant Toll.
With each rung lower in the chain, the remuneration comes with fewer benefits and more strings attached.
The 60-year-old driver says working for a bigger company often means getting paid extra rates for time spent loading and unloading a vehicle.
But you won't get paid extra working for a smaller firm, putting more pressure on drivers to make up time on the road, or skip breaks.
One industry study, a survey of 402 truck drivers in 1990, by David Hensher, Professor of Management at the Institute of Transport and Logistics Studies at Sydney University, found drivers who were most likely to operate dangerously were the newest to the industry and paid the least.
They were not necessarily owner drivers. Rather, like Lennons and George, they were younger drivers working for smaller firms.
''Small company employee drivers have some of the worst industry practices in respect of speeding, use of stimulants and incidence of fines,'' Hensher's study found.
Later work by Ann Williamson of the University of NSW showed stimulant drug use was two to three times more likely for drivers paid on a by-results or contingency payment.
Then there are the client demands. In just one of many examples drawn out in a seminal inquiry into the industry in 2001 by Professor Michael Quinlan of the University of NSW it was shown some of the speeds in which produce was often transported across the country was not legally possible.
Mangos from the Bowen Basin, for example, were picked on a Friday afternoon and were then being delivered into Sydney within 39 hours - often by the one driver.
''Even at an average speed of 90km/h - an heroic assumption given road conditions and speed limits - the driving time would be around 33 hours or in excess of the legal driving limits,'' the inquiry said.
By definition this could not be legal. Drivers are required to have a seven-hour break between shifts.
In some respects the industry can point to an improving safety record. Since 1991 the number of fatal crashes involving heavy vehicles has remained relatively constant, but the number of trucks on the road has grown.
Nevertheless, drivers the Herald spoke to this week say plenty of the unsafe practices continue.
As a remedy, the Transport Workers Union has been campaigning on a ''safe rates'' agenda to codify a fairer remuneration structure for drivers, to prevent them having to skip breaks or catch up time with speed. The federal government has introduced legislation.
And the NSW Police and Roads and Maritime Services, meanwhile, will keep investigating Lennons.
with Jonathan Swan