a modification for American Truck Simulator adjusting trailers for overweight hauling

ATS HH49XVolvo

Modifies cargo weight-limit, weight, and mass ratios of owned lowboy trailers allowing more cargo options in consideration of rules for extra-legal non-divisible loads of each state and Western Regional Permit (WRP) for in-game highways and bridges. Also affects lowboy trailers in Freight Market. One cargo item also modified. Optional colored route map provided for more gameplay depth.

Basically I wanted to take advantage of my 8x6 (or 8x4) truck to carry more cargo on a single tridem lowboy trailer! A 6x4 truck may take heavier cargo, too.

For do-it-yourself or customizing, see “Modify Trailers for American Truck Simulator” handy to make changes to better suit your truck or your maps. The how-to post also covers creating and maintaining a modification. For those new to the game looking for advanced options see my post on preference suggestions.

Questions and feedback appreciated on Discord - DracoTorre Mods

ATS HHTTitle 320

version 1.48.DT.2.0 (2023 July 25) for American Truck Simulator 1.48


Requires game version 1.48 or newer!

old compatibility versions

Requires Heavy Cargo DLC

additional resource pages

table of contents


American Truck Simulator SCS Software

This modification tagged as mod-optional for convoy – untested

recommend heavy-duty wheels and tires available from:

recommended cargo packs:

ATS HHTiresFront

heavy-duty front wide tires


Recommend game version 1.48 or newer. For older game versions please download Heavy-Haul version v1.47.DT.1.9.

If on a job using a double or triple tandem lowboy trailer, finish the job to empty the trailer. When trying out this mod consider making a backup copy of your save or testing on a different profile.

  1. copy DTHHTrailerDef.zip into folder, /American Truck Simulator/mod/ (within your Documents)
  2. in game open the mod manager
  3. activate DTHHTrailerDef and sort as needed in consideration of compatibility


Simply copy-and-overwrite DTHHTrailerDef.zip into folder, /American Truck Simulator/mod/

intended use / recommendations

Please note the crawler tractor barely clears some enclosed load/unload positions. Optionally consider choosing appropriate parking such as safe. Shown in the image below apparently the overhanging lights may not impede parking.



barely clears with modified trailer - will not happen in unmodified game

Most loads should meet Washington (green routes), Oregon (light-green routes), and Western Regional Permit (WRP) Guide when using 8x6 or 8x4 truck with tridem lowboy trailer or tridem with booster (3+1) trailer, and using a 6x4 truck with other configurations. In Oklahoma (dark blue) limit is lower for tandem axle-group and higher for tridem. Other states (light-blue and gray routes) allow heavier cargo. Please note when using the 3+1 the heaviest loads (scraper, heavy bulldozer) may exceed green route weight limits with an 8x4 (or 8x6) semi-truck over 23500 pounds.

See optional heavy-haul route map page to observe bridge, length, and other restrictions with charts showing suggested cargo weight per trailer.

6x4 truck 50-foot tridem lowboy trailer:

  • cable reel is too heavy
  • in OK,ND,SD cargo at or under 24 tons (48000 lbs)
  • in Washington and Oregon cargo at or under 28 tons (56000 lbs) such as crawler tractor
  • in AZ,CA,CO,MT,NV,NM,TX,WY may haul tamping machine

6x4 truck tridem-with-booster (3+1) trailer:

  • all-terrain crane and Volvo L250H are too heavy
  • in OK,ND,SD cargo at or under 29 tons (58000 lbs) like the tamping machine
  • in in other states cable reel and lighter cargo

8x4 truck tridem-with-bosoter (3+1) trailer:

  • in Washington State to meet weight limit hauling heavy bulldozer or scraper use a day cab
  • in New Mexico to meet 90-foot length limit use a day cab

game limitations

Let us acknowledge game limitations relevant to changes this mod makes. As of game version 1.48:

  • scales only reveal total GVW without ability to determine axle-group weights
  • weigh stations allow all to proceed regardless of weight
  • no managed permits for oversized loads or no apparent fees applied
  • some cargo items on single trailer configuration may be too tall to clear some load/unload positions

Adhering to weight limits by route is player’s choice. By weight the beet harvester could be allowed on the modified single tridem lowboy, but due to the machine being too tall to clear some parking locations this modification adjusts the beet harvester cargo definition to limit it to double- and triple-trailer configurations. Same with the cotton harvester added to Heavy Cargo pack for game version 1.46.


Modifies definition files (found in def.scs) for owned lowboy trailers and the beet harvester cargo. May be incompatible with other modifications of the same files. No new content added. If another mod changes the beet harvester cargo give this mod priority else understand a chance the load may generate where it does not fit.

Files modified:

  • def/vehicle/trailer_owned/scs.lowboy/chassis/* (8 files)
  • def/vehicle/trailer_defs/scs.lowboy.* (30 files)
  • def/cargo/beet_harvester.sui
  • def\cargo\cott_harvest.dlc_heavy_cargo.sui (optional in game version 1.48)

summary of changes

  • tridem lowboy trailers increased weight limits except highest tier triple (3+3+3) remaining the same
  • tandem lowboy single trailer with a small increase in weight limit
  • tandem lowboy double and triple trailers reduced weight limits to observe assumed trailer rating
  • small increase to weights of double and triple trailer combinations
  • mass ratios adjusted for double and triple combinations

To estimate heaviest cargo, or weight limit, for each tridem trailer this modification observes the following:

  • Western Regional Permit Desk Guide (PDF)
  • each in-game state as of game version 1.45 plus Texas and Oklahoma
  • assumed trailer ratings and truck axle ratings
  • using center-of-mass formula to find axle group with maximum weight then estimating weight on remaining axle groups
  • avoid game generating disallowed loads within state (Washington) with most strict weight limits

Modified heaviest cargo per trailer:

  • single tridem lowboy: cable reel
  • double tandem-with-jeep (2+2): tamping machine
  • triple tandem (2+2+2): all-terrain crane, Volvo L250H
  • double tridem-with-booster (3+1): (scraper, heavy bulldozer,)** all-terrain crane, Volvo L250H
  • triple tridem (2+3+2): milling machine, log loader
  • triple tridem (3+3+2): lift truck, log stacker

**may exceed Washington State and green routes weight limit for 8x4 (or 8x6) semi-truck over 23500 pounds

again, some loads may be too heavy for a 6x4 truck - advise 8x6 or 8x4:

  • single tridem lowboy - cable reel
  • double tridem-with-booster (3+1) - scraper, heavy bulldozer, all-terrain crane, Volvo L250H


8x4 Peterbilt 389, modified tridem-with-booster (3+1) lowboy trailer hauling Volvo L250H



  • updated mod-package format to support game version 1.48 to make Heavy Cargo DLC optional
  • – if player lacks Heavy Cargo DLC will not mount changes made to these cargos


  • definition files updated with comments showing changes SCS made to default trailer weight limits for game version 1.47
  • cotton harvester cargo name updated to match SCS change; will show correct name
  • double tridem with booster (3+1) now accepts heavier cargos, heavy bulldozer and scraper (in Washington State recommend 8x4/8x6 day-cab)


  • handles overheight cotton harvester from Heavy Cargo pack to avoid loading on single tridem lowboy trailer

play suggestions

The game does not manage oversize or overweight permits and the weigh stations do not fine for being overweight, but players may wish to observe bridge weight limits or other oversized rules. Below I share some ideas.

Choose your truck and optionally check the colored Heavy Haul Route Map to determine heaviest cargo or best trailer to meet route restrictions which may include overall length. Weight of the trailer found by selecting trailer in the Trailer Manager menu then click on trailer image. Find your semi-truck weight, preferably full of fuel, at a paid scale found at some truck stops.

See the Western Regional Permit Desk Guide (PDF) which for loads under 160000 lbs (80 US tons) GVW, less than overall 110 feet length, and meeting its axle-group weight tables may travel on single permit through participating states. The route map indicates states participating with Western Regional Agreement by background having green tint which meets the green route weight limits.


Consider data for the mod, the route map, and the charts simplified in consideration of game limitations and the spirit of gaming. Do not rely on route map, charts, or modifed game data for real-world usage. I am a software developer having no experience with truck driving or in transportation. My goal in using references based on real-world information was to improve my enjoyment without necessarily making the game more realistic.

Design notes

Read a full explanation on my assumptions and how to modify to your liking on “Modify Trailers for American Truck Simulator”. In short I noticed lowboy trailers had the same weight limit as flatbeds (and others) and that real-world lowboys carry heavier cargo. So I set a goal to reasonably increase weight-limits for lowboys. The recently added drop deck trailers (game version 1.44) have weight limits 500 kg higher than un-modified lowboys and flatbeds having same axle count. I decided to keep weight-limit well below GVWR, avoid jobs spawning loads too heavy for a region, and for extra fun observe bridge weight limits. How to decide? I started reviewing real-world trailers and state heavy-haul rules.

After some consideration of New Mexico’s 90-foot overrall length limit, I later decided to allow heavier cargo for the tridem with booster (3+1) trailer since a tri-drive 49X day cab at 23500 pounds should meet Washington State and green route weight limit. When driving an 8x4 sleeper with 3+1 lowboy watch your weight in Washington and check your length in New Mexico. See my 1.9 update post for more details and a truck-length diagram.

See “Modify Trailers for American Truck Simulator” for more details and at the bottom of that page, the reference section.

permission and credits

Modification by David G Shrock, DracoTorre. You may alter values to your liking with credit. Please do not distribute on websites or Steam Workshop. Instead, please share link to this page.

Thanks to SCS Software.

Tools used:

ATS HH49XBoise 1200

Thank you. Feedback and questions welcome on Discord - DracoTorre Mods.

My World of Trucks profile page

American Trucking Simulator is a trademark of SCS Software. All other trademarks belong to their respective owners.