Project: Security of Cross Loaded Timber

Reference: S0044/VE

Last update: 09/09/2003 15:56:25


The project objective is to investigate what is safe and what is not safe with regard to vehicle loading practices. The project may make recommendations for change to ensure safe operation is in use on the roads.


This project is a collaborative initiative with the Health and Safety Executive (HSE). The project was initiated after fatal accidents involving flat bed vehicles carrying crossloaded 2.0m - 2.5m long timber logs. The Timber Federation and HSE are concerned about the risks of individual timbers being ejected from apparently secure loads.

This method of loading can have the effect of significantly raising the vehicle centre of gravity compared with unladen and laden conditions. This will affect the stability of the vehicle, particularly when cornering or traversing rugged uneven terrain. These vehicles are moving timber from logging sites that are normally accessed from unmade roads and tracks, which can increase the risk.

The project will:

* review current practice in conjunction with the Timber Federation;
* carry out trials on flatbed vehicles loaded with logs to assess the restraint requirements for this mode of loading;
* establish the load shedding mechanism;
* identify the factors which trigger load movement; and
* consider methods to restrain the load.


TRL Limited
Crowthorne House, Nine Mile Ride, Wokingham, Berkshire, RG40 3GA
+44 (0)1344 773131

Contract details

Cost to the Department: £53,000.00

Actual start date: 06 August 2001

Actual completion date: 30 November 2002


PR/SE/514/2002. The Security of Cross Loaded Round Timber
Author: TRL Ltd
Publication date: 01/11/2002
Source: Contact

Summary of results

  1. Calculations predicted that the threshold acceleration for rollover of an articulated large goods vehicle carrying a flat-topped load would be 0.41g. The test programme showed that rollover can occur during a roundabout manoeuvre at 40km/hr where this lateral acceleration threshold was exceeded. In this instance, the loss of the load occurred after the vehicle started to roll. A further loss of load occurred when an attempt at a 100m radius circle test at 70km/hr was made.

    During testing of both the 38 tonne flat topped load and the 44 tonne convex topped load, the log load was seen to move sideways. Sideways movement (bowing) of the load was also noticeable during a static tilt test. For this test the load was secured following the Road Haulage of Round Timber Code of Practice.

    This research has highlighted two areas that need to be considered in order to improve the safety of timber haulage, load position and restraint and the height of the centre of gravity of the vehicle.