Volumetric concrete mixers: call for evidence outcome
Updated 18 March 2025
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Introduction
The Department for Transport (DfT) commissioned a report through National Highways (NH) on the impact on existing bridge structures from higher weight volumetric concrete mixers (VCMs) permitted under the current temporary arrangement to inform future decisions. The final report provides a summary of findings related to the viability of allowing VCMs to continue operating at higher weights.
The report compared the forces exerted by the VCMs to the standard highway vehicle load model used for assessing bridges and found the effects were up to 17% greater than for vehicles complying with the current standard weight limits. This will likely result in increased wear and tear and may impact the durability and lifespan of existing bridges. In addition to the impact on bridges, heavier vehicles also put more stress on roads.
Overload is likely to result in increased wear and tear to bridge elements and components. For example, this could lead to:
- cracking to concrete bridges
- accelerated deterioration of expansion joints
- increased wearing of surfacing
Significant resources and funding will need to be diverted to manage structures overloaded by VCMs.
In addition to the impact on bridges, heavier vehicles also put more stress on roads. Increasing the weight limit for 4 axle VCMs from 32 tonnes to 38.4 tonnes could more than double the average road wear per vehicle, which impacts maintenance costs and safety.
The implications from the NH report are that the continued operation of higher weight VCMs is not sustainable. This means that the only viable options from the call for evidence are:
- option 1: ‘do nothing’
- option 2: ‘advanced route notification’
Responses to the call for evidence highlighted concerns for option 2.
Next steps
The current policy position will be maintained. This allows VCMs to operate at increased weights via vehicle special orders (VSOs) until 2028 or the 12th anniversary of the vehicle’s first registration, whichever comes sooner.
This arrangement, implemented in 2018, permits VCMs to operate at up to 38.4 tonnes for 4 axle rigid vehicles and up to 44 tonnes for 5 axle articulated vehicles.
The length of the arrangement was agreed to provide sufficient time for industry to transition to compliant vehicles. At the end of the temporary arrangement, VCMs must operate at the legal weight limits applicable to other heavy goods vehicles.