Navigating Volumetric Concrete Mixer Weight Limits

Volumetric Concrete Mixers (VCMs), often referred to as mobile concrete batching plants, are indispensable assets in the construction industry across the UK. Their ability to carry all the necessary components for concrete and mix them on-site provides unparalleled flexibility, significantly reducing waste and helping to keep project costs firmly under control. However, these highly specialised vehicles operate within a complex regulatory landscape, particularly concerning their weight limits, which has been a subject of ongoing discussion and change.

The journey to the current regulatory environment for VCMs has been anything but straightforward. Significant shifts occurred in 2017 and 2018 when long-standing exemptions from annual vehicle testing and operator licensing were rescinded. These changes fundamentally altered how VCMs are categorised and regulated, bringing them more in line with other Heavy Goods Vehicles (HGVs). This article delves into the intricacies of VCM weights, the regulatory rationale behind these changes, and the potential future for these essential construction workhorses, including their estimated unladen weight of 19 tonnes.

Understanding Volumetric Concrete Mixers and Their Regulatory Journey

Unlike traditional 'barrel' concrete mixers that deliver pre-mixed concrete, VCMs are designed to batch concrete on demand. They carry separate compartments for aggregates, cement, water, and admixtures, allowing for precise mixing tailored to specific job requirements. This 'just-in-time' approach minimises spoilage and ensures optimal concrete freshness, a crucial factor for many construction applications. Their unique operational model, however, previously afforded them certain regulatory exemptions.

The Shift in Operator Licensing

Prior to the Goods and Motor Vehicles (Miscellaneous Amendments) Regulations 2018, VCMs were largely exempt from goods vehicle operator licensing under a specific legal provision for 'engineering plant'. This exemption applied to vehicles with mounted fixed plant or machinery that also carried goods (materials) for use with that plant. The industry widely believed this meant VCMs could operate up to their chassis design weight and were exempt from HGV driver licensing rules, a significant advantage over traditional barrel mixers that had no such exemption.

However, a public consultation in 2014-2015 revealed broad support for removing this exemption. The primary drivers were concerns over fair competition with other goods vehicles, which were already subject to stringent operator licensing, and paramount road safety considerations. The government's decision in 2017 to include VCMs within the scope of operator licensing aimed to ensure a level playing field and promote safer road practices, bringing them under the same regulatory regime as most HGVs.

Vehicle Testing and Plating: A New Era of Scrutiny

Parallel to the changes in operator licensing, the Department for Transport (DfT) also moved to remove exemptions from roadworthiness testing for certain specialised heavy vehicles, including VCMs. Previously, many large and heavy vehicles had been exempt from the Goods Vehicles (Plating and Testing) Regulations 1988, which mandate annual roadworthiness tests (akin to MOTs for lighter vehicles) and set technical standards. The rationale for removing these exemptions was clear: to reduce vehicle defects and, consequently, the number of road traffic collisions linked to such defects.

A key aspect of heavy vehicle testing is 'plating', where the Driver and Vehicle Standards Agency (DVSA) issues a plating certificate. This certificate, given before a vehicle's first test, denotes its maximum vehicle weight and maximum train weight, aiding both testing and enforcement. With the removal of testing exemptions in 2017, the default scope of plating was also applied to VCMs. It's important to note, however, that VCMs currently operating at higher weights under Vehicle Special Orders (VSOs) remain exempt from these plating requirements, adding another layer of complexity to their regulation.

Temporary Weight Limits Dispensation: A Transitional Measure

Recognising the substantial investment made by the industry in VCMs designed to operate above standard weight limits, the DfT introduced a temporary arrangement. This dispensation, effective from 2018, allows a limited number of VCMs to operate at elevated weights:

• 38.4 tonnes for 4-axle rigid VCMs
• 44 tonnes for the rarer 5-axle rigid examples

This arrangement is intended as a transitional measure, allowing VCM operators a period to adapt to standard weights. It is set to expire in 2028 or on the 12th anniversary of the vehicle's registration, whichever comes first. The controlled number of vehicles operating under these VSOs aims to prevent breaches of standard bridge tolerances and avoid setting an unintended precedent for general HGV operations.

However, this temporary allowance comes with a significant caveat: even a small increase in axle weight can drastically increase road wear. DfT research indicates that a mere 10% weight increase can lead to approximately a 44% increase in certain types of road wear. This highlights the substantial infrastructure costs and environmental impact associated with permitting VCMs to operate at higher weights indefinitely.

The DfT estimates the average unladen weight of a volumetric concrete mixer (VCM) is 19 tonnes. This is a crucial figure when considering the total permissible laden weight and the potential payload. When operating at the standard 32-tonne maximum authorised weight for 4-axle rigid goods vehicles, VCMs incur a substantial payload penalty compared to barrel concrete mixers. This penalty is estimated to be similar to the 6.4 tonnes extra allowed via the temporary VSOs for 4-axle vehicles.

The Call for Evidence: Shaping the Future of VCM Weights

The DfT is currently undertaking a 'call for evidence' to assess whether there is sufficient justification to amend the current policy approach to VCM weight limits. This follows the initial decision to bring VCMs into line with the standard 32-tonne weight limit, driven by concerns for fair competition, increased road safety risks, and infrastructure costs (e.g., bridge damage, road wear). The ongoing National Highways feasibility study on structures will heavily influence any future decisions.

The call for evidence seeks input from all interested parties, including vehicle operators, manufacturers, trade bodies, and road authorities. It aims to understand the implications of various potential long-term changes, including maintaining the current temporary dispensation, the challenges involved, and any safety or environmental concerns that may arise.

Comparison of Weight Limits and Structural Impact

Standard vehicle weights are governed by the Road Vehicles (Authorised Weight) Regulations 1998, which typically set a maximum authorised weight of 32 tonnes for motor vehicles with four or more axles. While there have been recent amendments for zero-emission vehicles and longer semi-trailers, these changes do not permit operations outside of standard structural design parameters or at heavier weights than similar conventionally powered or standard-sized combinations.

A 2017 study by National Highways (then Highways England) specifically examined the impact of VCMs operating above standard weights. It concluded that VCMs operating at 41.48 tonnes (4-axle) or 44 tonnes (5-axle) would cause load effects greater than those used for bridge assessments. This implies a significant risk of excess wear and damage to structures, particularly with repeated use. Despite this, VCMs operating under the current temporary VSOs are not required to notify bridge owners in advance of their operations, a practice recommended by the National Highways study for such heavy loads.

It is the DfT's current view that VCMs do not meet the strict definition of an 'engineering plant' under the Special Types General Order (STGO) 2003, which allows certain specialised heavy vehicles to operate at higher weights. The STGO definition requires a vehicle to be "specially designed and constructed for the special purposes of engineering operations" and that the operation "cannot be safely carried out by a motor vehicle or trailer that complies in all respects with construction and use and goods vehicle type approval regulations." The DfT believes VCMs can, in fact, be safely operated in conformity with standard regulations, including the 32-tonne limit.

Proposed Options for the Future of VCM Weight Limits

The DfT has outlined three potential options for the future regulation of VCM weight limits beyond the expiry of the current temporary arrangement in 2028. These options will be subject to the conclusions of the National Highways structural assessment study.

Option 1: Maintain the Current Exceptional Temporary Arrangement

This 'no change' option would see the existing VSOs continue until their planned expiry dates (2028 or 12th anniversary of registration). It provides operators with a defined period to transition to the standard lower weight limits for VCMs, bringing them into alignment with other goods vehicles and ensuring they fall within the load models used for bridge assessments. While offering a clear endpoint, it means continued operation at weights that cause increased road wear until the transition is complete.

Option 2: Allow All VCMs to Operate at Temporary VSO Weights with Advanced Route Notifications

This option proposes a permanent solution where VCMs could operate at the higher temporary VSO weights (38.4T for 4-axle, 44T for 5-axle) but would require operators to provide advanced notification of their intended routes. This practice mirrors that used for Category 1 abnormal indivisible loads (AILs), where operators must give at least two clear working days' notice to police, highway authorities, and bridge/structure owners (e.g., National Highways, Network Rail) via systems like ESDAL (Electronic Service Delivery for Abnormal Loads).

Pros:

• Allows VCMs to maintain higher payloads, potentially reducing the number of journeys required.
• Provides a mechanism for authorities to assess routes and identify weaker structures, mitigating some infrastructure risks.
• Aligns VCM operations more closely with other heavy, specialised vehicle movements.

Cons:

• Requires significant operational planning and administrative burden for operators, especially for spontaneous or short-notice jobs.
• May not be viable for all VCM operations, particularly those on constrained sites or minor roads requiring immediate deployment.
• Represents a significant legal adaptation for vehicles that, in DfT's view, can technically operate within standard weights.

This option is seen as a significant legal development in the use of the notification system, which is currently reserved for vehicles that cannot be designed or operated at standard weights and dimensions, or for loads that are physically indivisible.

Option 3: Allow for Further VSOs Until Further Notice, Subject to Vehicle Age and DVSA Earned Recognition Accreditation

This option would extend the VSO mechanism indefinitely, allowing post-2018 vehicles to operate at increased weights (same as 2018 VSOs) for 12 years post-registration, provided the operator is accredited by the DVSA for their Earned Recognition scheme. The VSO scheme would continue to be administered by the Vehicle Certification Agency (VCA) on a per-operator basis.

Pros:

• Provides a long-term solution for operators wishing to utilise higher payloads.
• Encourages participation in a scheme based on high compliance and safety standards, as operators must regularly share performance information with DVSA.
• Allows VCMs to operate across the wider road network, except where local weight restrictions are in place.

Cons:

• Continues the risk of excess damage to weaker bridges, especially in areas with repeated VCM operations, as advance notification is not required.
• Extends what was initially designed as a temporary, transitional approach into an enduring one, potentially undermining the principle of bringing VCMs into standard regulatory compliance.
• Requires operators to maintain Earned Recognition status, with potential VSO revocation if status is lost.

The Earned Recognition scheme is a voluntary programme for operators with at least two years of operator licence history, designed to prove adherence to driver and vehicle standards. DVSA has even developed specific Concrete operational audit standards in partnership with the British Aggregates Association to support this.

Important Considerations and Potential Effects

Any enduring change to VCM weight limits must be assessed for its utility, safety, potential adverse side effects, and fairness, ensuring compliance with competition law and the public sector equality duty.

Environmental and Economic Impacts

Allowing VCMs to carry more weight per journey could lead to fewer overall journeys, which would have positive environmental implications, including reduced carbon emissions, lower congestion, and improved air quality. However, the DfT's internal analysis estimates that increasing the weight limit for 4-axle VCMs from 32 tonnes to 38.4 tonnes could increase average road wear by between 110% and 220% per vehicle, depending heavily on the vehicle's loading. This significant increase in road wear would translate to higher infrastructure maintenance costs for the taxpayer.

From a commercial perspective, maintaining higher weight allowances could significantly impact the profitability of VCM operators by enabling larger payloads and potentially reducing operational costs per cubic metre of concrete. However, this also raises questions about fair competition with traditional barrel mixers and other goods vehicles that must adhere strictly to standard plated weight limits.

Safety Concerns

Operating vehicles at heavy loads, even within their manufactured design weights, places increased pressure on braking systems, tyres, and other vehicle components. Vehicles overloaded beyond their design weight are less stable, harder to steer, and take longer to stop, dramatically increasing the risk of serious incidents. Construction-related vehicles, including VCMs, have been a focus for enforcement and safety initiatives, particularly in urban areas like London, to mitigate risks to cyclists and pedestrians.

The DfT is keen to gather evidence on compliance and safety issues associated with VCM operations at heavy loads, even under existing VSOs. The fact that rigid goods vehicles in excess of 32 tonnes are extremely rare in the UK means there is no direct international comparator case, making robust safety evidence even more critical.

Frequently Asked Questions (FAQs)

The Road Ahead

The future of VCM operations in Great Britain hinges on the outcome of the DfT's call for evidence and the National Highways feasibility study. The decisions made will balance the commercial needs of the construction industry with critical considerations for road safety, infrastructure integrity, environmental impact, and fair competition. As stakeholders provide their insights, the path forward will become clearer, determining whether VCMs will continue to operate under special dispensations, transition to standard weight limits with new notification requirements, or embrace a system tied to advanced compliance schemes like Earned Recognition.

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