The plated weight for the Volvo in
Ethel's link is not 4.4t, it is 44t. This is not the tare of the unit.
In the many years that I operated a weighbridge I never encountered a cab weighing as little as 4 tonnes; this is especially true of a 6x4. You would only
approach that kind of weight with a daycab 4x2 used as a shunter. As a comparison, a Ford Mondeo weighs over 1.5t.
Perhaps showing how outdated I am but at that time 38t was the maximum weight permitted for road transport, which worked out to a 40' triaxle curtainside trailer and its unit (any axle combination) legally able to carry no more than a 23t payload, thus giving a minimum tare for the unit+trailer of around 15t. An empty curtainsider should account for less than half of that weight.
This
ERF (6x2) weighs 7.26t. with no fuel or driver.
This
MAN ERF (6x2) with full fuel tanks - 7.74t.
Daf's (4x2) ranging from 7.2t to 7.9t.
Mercedes-Benz Actros (4x2) - 7.04t
Mercedes-Benz Actros (6x2) fuel and driver - 8.488t.
Renaults, Volvos and Scanias tend to be at the heavier end of the market.