Understanding CEN/TS 16786

CEN/TS 16786 is a European Technical Specification that establishes standards for TMAs (Truck Mounted Attenuators), which are critical safety devices used in road construction and maintenance operations. Developed by the European Committee for Standardization (CEN), this specification provides comprehensive guidelines for testing and evaluating TMA performance.

Purpose and Scope

CEN/TS 16786 specifically addresses whole Truck Mounted Attenuator systems under impact conditions. TMAs are designed to protect occupants of vehicles that might collide with the rear of stationary or slow-moving trucks in work zones. During an impact, the mobile carrier (truck) is accelerated forward as the impacting vehicle decelerates, which can create additional risks for road workers positioned in front of the support vehicle.

Key Components of the Standard

Performance Classes

The specification establishes three distinct speed classes for TMAs:

• Speed Class 50 (50 km/h)
• Speed Class 80 (80 km/h)
• Speed Class 100 (100 km/h)

Each class requires specific impact tests with different vehicle masses and approach angles to validate performance.

Test Parameters

The standard defines detailed requirements for:

• Test site conditions (surface type, friction requirements)
• Impacting vehicle specifications (mass, dimensions, age)
• Mobile carrier setup (transmission, brakes, steering angle)
• Test matrix for different speed classes

Test Procedures

Tests involve impacting the TMA with vehicles of specified masses (900 kg and 2,000 kg) at various speeds and angles. Key test approaches include:

• Head-on center impacts
• Offset impacts at 10° angles
• Tests with minimum and maximum specified whole system masses

Evaluation Criteria

Performance is evaluated based on several factors:

1. Structural adequacy - The TMA must demonstrate controlled stopping of the impact vehicle
2. Deformation - No penetration of passenger compartments by TMA components
3. Trajectory - The impacting vehicle must not roll over
4. Severity indices - Maximum values for Acceleration Severity Index (ASI) and Theoretical Head Impact Velocity (THIV)

Roll Ahead Distance

A critical measurement is the "roll ahead" distance - how far the mobile carrier moves forward during impact. This is particularly important for worker safety in front of the carrier vehicle.

Importance of Certification

Certification according to CEN/TS 16786 ensures that TMAs meet stringent performance and safety criteria. The certification involves rigorous impact testing that simulates real-world crash scenarios, assessing the TMA's ability to absorb energy and minimize damage and injury. This certification is recognized throughout Europe and signifies compliance with high safety standards.

Documentation and Reporting

The standard requires detailed documentation of test results, including:

• Video and photographic evidence
• Measurements of vehicle deformation
• Trajectory data
• Severity indices calculations
• Detailed damage assessment

By establishing consistent testing methodologies and performance requirements, CEN/TS 16786 plays a crucial role in improving road worker and driver safety throughout Europe.