December 2025: New Collision Force Standard for Bridge Safety in Automotive Engineering

Ensuring the safety and durability of bridges is paramount for the automotive and road vehicles sector, especially as traffic density and vehicle weights continue to rise across Europe. In December 2025, the publication of CEN/TR 18242:2025 introduces essential new guidance for determining the collision forces that bridges must withstand when impacted by errant vehicles striking vehicle restraint systems. This latest standard represents a significant step forward in harmonizing design best practices and safeguarding road infrastructure. This article explores the single but impactful standard released, offering professionals crucial details for compliance and safer infrastructure.

Overview / Introduction

The field of automotive and road vehicles engineering relies profoundly on robust standards to ensure that safety, performance, and reliability are woven into the fabric of infrastructure projects. Bridges—vital links in road networks—are especially vulnerable to the rising frequency and severity of vehicular impacts. Without a clear, uniform approach to quantifying these forces, designers risk both over- and under-engineering critical structures, which can lead to budget overruns or compromised public safety.

In this deep-dive article, you will learn:

• The scope, methodologies, and best practices set forth in CEN/TR 18242:2025
• Key requirements for analyzing and testing vehicle restraint systems (VRS) on bridges
• How to classify and implement VRS load levels accurately
• Practical insights for engineers, designers, compliance officers, and procurement teams

Detailed Standards Coverage

CEN/TR 18242:2025 - Determination of Collision Forces on Bridges from Vehicle Restraint System Impacts

Road restraint systems - Determination of collision forces on bridges as a result of an impact of a vehicle on a restraint system

Modern bridge design demands accurate, evidence-based calculations of the collision forces that vehicle restraint systems (VRS)—such as guardrails and parapets—may transmit to a structure during vehicular impacts. CEN/TR 18242:2025, developed by the European Committee for Standardization (CEN), fills a long-standing gap by cataloguing best-practice methodologies for this critical safety consideration.

Standard Scope and Methodology

The standard provides clear guidance for:

• Quantifying the forces transferred to bridge structures by errant vehicles striking a VRS
• Classifying restraint systems based on the loads they transmit
• Encouraging harmonization of approaches across member countries, many of which previously relied on disparate national methods

Analytical Determination

The document outlines comprehensive analytical methods, recommending designers:

• Analyze the moment (M) and horizontal load (H) for posts and barrier anchorages using clearly defined formulae
• Generate M/H curves for each major component, including posts, base plates, and anchorages
• Factor in the weakest element (determined by the lowest part of the M/H curve) to accurately predict force transmission

Distinct guidelines are provided for both discontinuous and continuous face barriers, addressing everything from post geometry to the effects of plinths and variable cross-sections. Heavy concrete barriers require evaluation of friction resistance, considering dead load and wheel load positions.

Testing-Aided Determination

In addition to calculations, CEN/TR 18242:2025 endorses:

• Laboratory test procedures where forces are measured directly via static (push-pull) or dynamic (impact) tests
• Testing at multiple heights and force distributions to simulate real-world impacts
• Detailed data acquisition protocols—including sampling rates, sensor placement, and post-processing to ensure reliability and comparability
• Use of both static and dynamic tests depending on whether systems are metal (suitable for dynamic) or heavy concrete (static only)

Testing not only validates design assumptions but also helps in characterizing how design parameters (such as anchorage, posts, or continuous barriers) impact load transmission and bridge safety.

Classification and Implementation

The methodology supports bridge engineers and suppliers by:

• Providing criteria for assigning VRS to load categories as referenced in EN 1991-2
• Linking classification directly to anchor design and containment levels, ensuring that selection and specification are informed by sound technical data
• Encouraging the use of realistic, not overly conservative, load assumptions to optimize both safety and cost

Who Should Comply

CEN/TR 18242:2025 will be of critical importance to:

• Bridge and infrastructure designers
• Civil and structural engineers responsible for VRS specification or installation
• Road safety authorities and regulatory bodies
• Manufacturers and suppliers of vehicle restraint systems
• Consultants engaged in bridge safety risk assessments

Practical Implications and Notable Advancements

• Reduces ambiguity and the risk of damaging bridge decks by promoting accurate force predictions
• Addresses both analytical and testing-based design approaches, accommodating varying national practices and bridge types
• Facilitates improved cross-border procurement, as road restraint equipment can now be compared and specified using standardized methods
• Supports lifecycle cost management and safer infrastructure

Key highlights:

• Comprehensive analytical and test-based options for determining VRS impact loads
• Harmonizes bridge safety methodologies across Europe
• Promotes realistic containment level selection and anchor design

Access the full standard:View CEN/TR 18242:2025 on iTeh Standards

Industry Impact & Compliance

The introduction of CEN/TR 18242:2025 marks a turning point for infrastructure safety management. With its publication, businesses operating in the automotive and road vehicle sector must:

• Review and update design practices for bridges with vehicle restraint systems
• Ensure that all new installations are analyzed using either the prescribed analytical or testing-aided methods
• Re-examine product specifications and procurement documents to comply with unified European standards
• Prepare documentation for regulatory review and client assurance based on the load classification methodologies

Benefits of Compliance:

• Enhanced bridge resilience: Accurate prediction and accommodation of VRS loads reduce the risk of catastrophic bridge failures
• Cost efficiency: Optimizing VRS selection avoids both under- and over-engineering
• Competitive differentiation: Early adopters of the standard can demonstrate commitment to safety and regulatory excellence

Non-compliance Risks:

• Increased liability from bridge damage or failure
• Delays in regulatory approvals and project handovers
• Potential incompatibility with cross-border procurement and project collaboration

The standard does not prescribe mandatory timelines for compliance, but industry best practice is to adopt new CEN guidance in current or upcoming projects, especially those where bridge strengthening or new installation is planned.

Technical Insights

CEN/TR 18242:2025 introduces several notable technical best practices for safer, more reliable infrastructure:

• Harmonized Analytical Calculations: Emphasizes the use of M/H curves calculated with referenced European standards (e.g., EN 1993-1-1, EN 1991-2)
• Enhanced Testing Protocols: Standardizes laboratory push-pull and dynamic tests (using impactors or load cells), improving the reliability of measured loads
• Data Acquisition Rigor: Specifies sampling rates and filtering (per ISO 6487) to ensure measurement accuracy in dynamic tests
• Flexible Design Approaches: Caters to both discontinuous (metal/anchored) and continuous (concrete/anchorage or friction-based) VRS designs
• Realistic Load Consideration: Encourages bridge designers to select realistic (rather than purely conservative) loads depending on proven system capacity

Implementation Best Practices:

1. Involve both analytical modeling and laboratory testing in VRS selection and bridge design
2. Maintain detailed technical documentation (drawings, anchorage details, material strengths)
3. Use EN 1991-2’s characteristic load levels as a baseline, but verify through standard-compliant testing
4. Regularly review containment level requirements in light of evolving traffic and vehicle characteristics

Testing and Certification Considerations:

• All laboratory tests should replicate installation conditions as closely as possible (use manufacturer-specified fixings and surfaces)
• For dynamic testing (metal barriers), ensure appropriate mass/speed and validated sensor configurations
• Data acquisition systems must be calibrated and compliant with ISO protocols
• Adequate training for laboratory and site personnel on proper force measurement and test interpretation

Conclusion / Next Steps

The December 2025 publication of CEN/TR 18242:2025 sets a new benchmark in automotive and road vehicle engineering for the design and verification of bridge restraint systems. This comprehensive approach to determining collision forces—integrating state-of-the-art analytical and testing guidance—enables bridge designers, engineers, and authorities to deliver safer, more reliable road infrastructure while optimizing project delivery and lifecycle cost.

Key takeaways:

• Road restraint systems on bridges must now feature evidence-driven force calculations and/or validated laboratory test data
• Uniform classification and load level assignment eliminate ambiguities and facilitate cross-border project collaboration
• Early adoption supports regulatory approval, public safety, and strategic market positioning

Recommended actions for organizations:

• Download and study the full text of CEN/TR 18242:2025
• Review all current and future bridge projects for compliance readiness
• Train design and compliance teams on updated methodologies
• Stay subscribed to iTeh Standards for timely updates on future automotive and infrastructure standards

Explore the latest automotive and road vehicle standards, including CEN/TR 18242:2025, on iTeh Standards. Stay ahead and ensure your projects meet evolving safety and compliance expectations.