I am a lorry driver and here the maximum weight of a full sized artic (semi truck) is 44 tons including load
I used to drive a tipper lorry carrying mostly scrap metal
and i have driven containers,refridgerated,tankers,flat beds,curtainsiders
almost all types of normal trucks available
Here are some stats (these are rough and from memory so close but not always perfect)
tipper.............empty 17 ton + 27 ton load (This one i remember well, my truck was 17.2 tons with full tank of diesel FH12 volvo globetrotter with trailer made of steel)
flat bed..........empty 13 ton + 31 ton load (I remember my old truck an FM12 weighed 12.8 tons empty)
Refrigerated...empty 18 ton + 26 ton load (this is a rough guess i know fridge trailers are heavy and weigh more than tippers so its close)
containers......empty 11 ton + container 4 ton + 29 ton load (i remember i could carry 29 tons with my Iveco Eurostar and worked out the rest from there
tanker..........empty 15 ton + 29 ton load (this is mostly a guess i cannot remember how heavy that truck was but this will be very close)
curtainsider..empty 14 ton + 30 ton load (this is again a guess but based on what i know from other truck types 14 ton sounds about right to me)
Horsepower
I will start with the best you can buy
volvo FH16..............610 BHP
Scania 416..............580 BHP
M.A.N.....................680 BHP (this is really for heavy haulege)
other companys do have a big power truck but i dont know exact figures
Not everybody drives high power truck so these are some of my recent truck with power output.
Scania 412....420 BHP
DAF XF ........430 BHP
Volvo FH12...460 BHP (this was my tipper lorry i loved it

)
Volvo FM12...380 BHP
DAF XF ........480 BHP
DAF CF........320 BHP
DAF CF........430 BHP
M.A.N..........460 BHP (old shape)
M.A.N..........410 BHP (new shape)
No particular order i just put them in as i remembered them this gives an idea of a typical Truck in england
I drive for an agency so i drive lots of different trucks with lots of different loads. Corner speeds for tankers tend to be low, for other types it depends on the load.
speed limit is
56 mph (90kmh) on motorways
40 mph (66kph) on normal roads
I hope this helps i must admit i like the heavy load ones but i would use a vertion with correct weights too

depending on what type of game i was playing