Tractor Trailer Tip Over's

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Construction Safety Association of Ontario

Summary Statement

Tractor-trailer dumping rigs can tip over while dumping, especially on an uneven surface with a load sticking in the top of the box while being raised.

Hazard Summary

Tractor trailers have tipped over while dumping loads of crushed quarry stone, fly ash, foundry sand, steel lathe turnings and other materials. There have been many such incidents, most involving long-box units.

Recently a truck driver was killed when he tried to enter the cab of his truck after the truck started to tip. The tip-over happened because steel turnings in the top of the box stuck together while it was being raised.

Conditions contributing to these tip-overs included:

  • uneven tire pressures,
  • poor suspension systems,
  • worn-out lifting components (including hinge pins),
  • defective lift cylinder components,
  • uneven or unstable dump areas,
  • reduced flow properties of materials, caused by freezing, moisture, compacting, etc.,
  • poor distribution of loads (they were top-heavy or had too much on one side),
  • strong winds, and
  • operator error.

Locations and Sectors

Mining, construction and industrial.


  • When loading the truck, distribute the load as evenly as possible (both side to side and end to end), and never put too much material at the upper end of the box.
  • In dumping materials, use a suitable combination of the following precautions:
    1. use bottom dump units or other, more stable, combinations of truck and dump unit;
    2. use a remote control for tipping the dump box so that the safety of the operator is not endangered, as required by the Regulations for Industrial Establishments (R.R.O. 851/90, section 45);
    3. dump at fixed locations where mechanical means are in place to prevent tip-overs (see R.R.O. 851/90, section 46);
    4. assign a trained observer to help the operator in situations where dumping will be carried out at many places on the same site (the observer would help the operator examine the truck and would direct the operation);
    5. use liners in the dump box to keep material from sticking; and
    6. use the truck's exhaust to heat the box and keep material from freezing.

  • Make sure that everyone in the dumping area is aware that a tip-over is possible.
  • There should be a daily inspection of the unit. This should include an examination of the tire pressures, the condition of the suspension components and the condition of dump box components, including the hinge pins and the lift cylinder.
  • Truck drivers and others should be trained in:
    1. how to examine the unit,
    2. safe methods of loading and dumping, and
    3. safe procedures for avoiding injury, specifying where to be while dumping is in progress and what to do if the truck starts to tip.

Please photocopy Ministry of Labour Alerts, distribute them widely and post them where people will see them.

Produced by the Mining Health and Safety Program, Ministry of Labour

Alert 15/1295 ISSN 1195-5228