Some foreign lorry drivers work such long hours they are reporting themselves to police to be sure they get a break from their cabs.
Tighter profits mean some firms are pushing drivers to work far over their hours, BBC Eye On Wales has found.
Police have come across drivers who have been at the wheel for 32 hours.
While they can take action against the foreign drivers flouting the rules it is much more difficult to prosecute overseas companies.
While lorries engaged in international journeys represent less than 1% of traffic on British roads, they are responsible for 8% of all road deaths.
Ch Supt Geraint Anwyl from North Wales Police leads the national roads policing forum.
He said he is concerned about their lack of control over foreign haulage companies who pressurise drivers into doing excessive hours.
Mr Anwyl said:"The drivers are committing offences, and clearly there's no excuse for that, but they're also victims in this - they are being exploited.
"It's a modern type of slave labour, in a sense.
He added: "We're able to do something with the UK-based operators, because there are traffic commissioners who issue the operators' licences and are able to place strict conditions and take punitive measures against companies who are offending.
"But the same system doesn't necessarily apply across Europe."
'Lost without her'
Dorothy Thomas, 63, from Amlwch on Anglesey, died in March when a German trucker crossed the road and hit her car head-on after 19 hours at the wheel.
Rolf Artmann, 54, was jailed for four years after admitting causing Mrs Thomas' death.
Mold Crown Court heard he had driven from Germany almost non-stop and the judge said he had shown deep remorse.
Gwyn Thomas, who was married for 42 years, is still struggling to come to terms with his loss, which he sees as wholly avoidable.
"If he had taken the rest, as the other drivers of two other vehicles which left Dortmund roughly about the same time, probably Dorothy would still have been alive today.
"It's very hard...I'm lost without her."
Meanwhile, British hauliers are under pressure to compete with their continental counterparts, in the face of disparity over fuel prices and road tax.
They are also frustrated at what they see as a lack of accountability by foreign operators.
Gill Sheddick, a former haulage operator and board member of the Freight Transport Association (FTA), said: "I think they try to enforce (the law) on foreign hauliers, and what happens is they take them to court, and they're issued with a fine, and the fine is never paid and the haulier is never chased.
"If you're a UK-based haulier, there is this corporate manslaughter issue being brought forward.
"But if you're a foreign operator, that doesn't apply to you, so that could could be an issue we should be pushing in Brussels, that it has to become a European-wide regulation."
Eye on Wales is broadcast at 1830 BST on Monday on BBC Radio Wales.
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