CEN/TS 16786:2018 (EUROPEAN TECHNICAL SPECIFICATION
FOR TRUCK MOUNTED ATTENUATORS)

WHAT IS CEN/TS 16786?
CEN/TS 16786:2018 is a European Technical Specification that defines the performance classes, impact test acceptance criteria, and testing methods for Truck Mounted Attenuators (TMAs). It establishes how complete TMA systems — including the attenuator, the host vehicle (mobile carrier), and the connection between them — should be tested under impact conditions. The specification was developed by CEN/TC 226 “Road Equipment” and serves as a provisional standard that may later be adopted as a full European Standard (EN).

TESTING AND SCOPE
The purpose is to determine the safety performance of TMAs under standardized, repeatable crash conditions. Testing evaluates:

• The severity of impact for vehicle occupants,
• the structural integrity of both the TMA and the carrier vehicle,
• and the post-impact trajectories of all vehicles involved.

It focuses purely on safety performance, not cost, maintenance, or aesthetics.

NORMATIVE REFERENCES
The testing methodology is aligned with several key European and international standards:

• EN 1317-1: Road restraint systems, general criteria for test methods
• EN 13036-4: Measurement of surface friction (Pendulum Test)
• ISO 8349: Determination of road surface friction
• ISO 10392: Determination of a vehicle’s center of gravity

TEST CONDITIONS
Test Site

• The test track must be paved (asphalt or concrete), long enough to measure roll-ahead distance
  and wide enough for vehicle trajectory evaluation.
• Friction must be measured using the Pendulum Test Value (PTV) under dry conditions.
• No surface contaminants (gravel, dust, polished asphalt, etc.) are permitted.

Test Vehicles

• Two vehicle masses are used: 900 kg / 1,984 lbs and 2,000 kg / 4,409 lbs, representative of typical European passenger cars.
• Vehicles must be less than 8 years old.
• The mobile carrier (truck or trailer) must meet load distribution requirements and may not exceed the manufacturer’s limits.
• An ATD (crash test dummy) is placed in the driver’s seat during 900 kg / 1,984 lbs tests.

TEST MATRIX AND SPEED CLASSES
TMA systems are tested under three standardised speed classes:

Each class includes several test “approaches,” covering maximum, minimum, and rigidly-blocked system masses to reflect different operational conditions.

MEASUREMENT ACCURACY

• Impact speed: within ±1% accuracy (allowable deviation −0% / +6%)
• Impact angle: within ±1.0° accuracy
• Combined tolerances for speed and angle are restricted to prevent excessive impact energy deviation
• Lateral displacement: within ±0.10 m at contact

EVALUATION CRITERIA
The overall system must meet the defined test and performance requirements. Acceptable TMA performance is demonstrated through controlled deceleration of the impacting vehicle without excessive intrusion or detachment.

1. Structural Adequacy
The TMA must bring the impacting vehicle to a controlled stop without excessive intrusion or structural failure.

2. Deformation

• No part of the TMA may penetrate the occupant compartment.
• Detached parts (>2 kg / 4.4 lbs) must not strike or endanger the carrier vehicle or surrounding area.

3. Vehicle Trajectory
The impacting vehicle must not roll over or overturn.

4. Severity Indices

SUMMARY
CEN/TS 16786:2018 provides a harmonized European procedure for evaluating the crash performance of Truck Mounted Attenuators. It ensures:

• Consistent and comparable test results across manufacturers,
• Objective measurement of occupant safety and system response,
• Clear classification of TMA systems by speed class and impact severity.