Manual for Assessing Safety Hardware
The AASHTO Manual for Assessing Safety Hardware (MASH) presents uniform guidelines for the crash testing of both permanent and temporary highway safety barriers and recommended evaluation criteria to assess test results. MASH guidelines and criteria, which have evolved over the past 40 years, incorporate current technology and the collective judgment and expertise of professionals in the field of roadside safety design. They provide:
1) a basis on which researchers and road agencies can compare the impact performance various safety barrier systems,
2) guidance for developers of new safety barrier systems, and
3) a basis on which road agencies can formulate performance specifications for safety barrier systems.
MASH is also the basis of testing procedures for road safety systems as stated in AS/NZS 3845.1: 2015 Road Safety Barrier Systems and Devices. The introduction of MASH follows changes to the vehicle fleet, researching of real-life impact conditions and updated criteria for evaluating barrier performance.
The underlying philosophy in the development of the MASH guidelines is that of “worst practical conditions.” The crash test parameters, such as the test vehicle, impact speed and angle combination, point of impact, test matrix, etc., specifies the worst, or most critical, conditions.
MASH Test Vehicles
Test Vehicle
Description
1100C
1100 kg Passenger Car
2270P
2270 kg Pickup truck
10,000S
10,000 kg Single-Unit truck
36,000V
36,000 kg Tractor-Van Trailer
36,000T
36,000 kg Tractor-Tank Trailer
Test Vehicle
1100C
Description
1100 kg Passenger Car
Test Vehicle
2270P
Description
2270 kg Pickup truck
Test Vehicle
10,000S
Description
10,000 kg Single-Unit truck
Test Vehicle
36,000V
Description
36,000 kg Tractor-Van Trailer
Test Vehicle
36,000T
Description
36,000 kg Tractor-Tank Trailer
MASH Evaluation of Longitudinal Barriers
MASH Test Level
Test Vehicle
Speed (km/h)
Angle (degrees)
Impact Severity (kJ)
1
1100C
2270P
50
50
25
25
18.9
39.1
2
1100C
2270P
70
70
25
25
37.1
76.6
3
1100C
2270P
100
100
25
25
75.8
156.4
4
1100C
2270P
10,000S
100
100
90
25
25
15
75.8
156.4
209.3
5
1100C
2270P
36,000V
100
100
80
25
25
15
75.8
156.4
595.4
6
1100C
2270P
36,000T
100
100
80
25
25
15
75.8
156.4
595.4
MASH Test Level
1
Test Vehicle
1100C
2270P
Speed (km/h)
50
50
Angle (degrees)
25
25
Impact Severity (kJ)
18.9
39.1
MASH Test Level
2
Test Vehicle
1100C
2270P
Speed (km/h)
70
70
Angle (degrees)
25
25
Impact Severity (kJ)
37.1
76.6
MASH Test Level
3
Test Vehicle
1100C
2270P
Speed (km/h)
100
100
Angle (degrees)
25
25
Impact Severity (kJ)
75.8
156.4
MASH Test Level
4
Test Vehicle
1100C
2270P
10,000S
Speed (km/h)
100
100
90
Angle (degrees)
25
25
15
Impact Severity (kJ)
75.8
156.4
209.3
MASH Test Level
5
Test Vehicle
1100C
2270P
36,000V
Speed (km/h)
100
100
80
Angle (degrees)
25
25
15
Impact Severity (kJ)
75.8
156.4
595.4
MASH Test Level
6
Test Vehicle
1100C
2270P
36,000T
Speed (km/h)
100
100
80
Angle (degrees)
25
25
15
Impact Severity (kJ)
75.8
156.4
595.4
Frequently Asked Questions
What is MASH?
The AASHTO Manual for Assessing Safety Hardware (MASH) is an update to and supersedes NCHRP Report 350 for the purposes of evaluating new safety hardware devices. MASH is also the basis of testing procedures for road safety systems as stated in AS/NZS 3845.1: 2015 Road Safety Barrier System and Devices. MASH guidelines and evaluation criteria incorporate current technology and the collective judgement and expertise of professionals in the field of roadside safety design.
Who is AAHTO?
The American Association of State Highway and Transportation Officials (AASTHO) is an international leader in setting technical standards for all phases of highway system development. Standards are issued for design, construction of highways and bridges, materials, and many other technical areas.
What are some of the differences between MASH and NCHRP Report 350?
Major improvements adopted by MASH when compared to NCHRP 350 include:
- Changes to the test vehicles to reflect modern vehicle fleets.
- Changes to the number and impact conditions of the test matrices.
- Changes to the evaluation criteria.
- Addition of new features to the test guidelines.
Do I need to replace barriers crash tested to NCHRP Report 350?
No. Australian State Road Agencies have reclassified non-MASH tested road safety barriers as Legacy Status. Safety barrier systems with a legacy status may be maintained until the end of their service life, or when parts are no longer available, however there shall be no new installations of permanent products with legacy status.
What is the underlying philosophy in the development of MASH test guidelines?
The underlying philosophy in the development of the MASH guidelines is that of ‘worst practical conditions.’ When selecting test parameters, such as the test vehicle, impact speed and angle combination, point of impact, test matrix, etc., every effort is made to specify the worst, or most critical, conditions. The impact speed and angle combination represents approximately the 93rd percentile of real-world crashes, i.e., only seven (7) percent of crashes are more severe. When the combined effects of all testing parameters are considered, the testing represents the extremes of impact conditions to be expected in real-world situations. It is also implicitly assumed that, if a roadside safety feature performs satisfactorily at the two extremes, then the feature would also work well for all impact conditions in between. This assumption has shown to be reasonable for most roadside safety barriers.
What is the upper performance level for the evaluation of terminals and crash cushions?
MASH Test Level 3 is the upper test level for the evaluation of terminals and crash cushions. The heavy vehicle impact is performed with a 2270 kg pickup truck travelling at 100 km/h.
What are the MASH evaluation criteria?
Crash testing of a safety barrier system in accordance with MASH should satisfy three (3) evaluation factors:
- Structural adequacy.
- Occupant risk.
- Post-impact vehicular response.
What is Structural Adequacy?
Depending on its intended function, the safety barrier system may satisfy structural adequacy by redirecting the vehicle, by stopping the vehicle in a controlled manner, or by permitting the vehicle to break through the system.
What is the MASH criteria for Occupant Risk?
Detached elements, fragments, or other debris from the test article should not penetrate or show potential for penetrating the occupant compartment, or present likelihood to impact with other traffic, pedestrians, or workers in a construction zone if applicable. For the majority of tests, a key requirement for occupant risk evaluation is for the impacting vehicle to remain upright during and after the collision. As an indication of vehicle stability, the maximum roll or pitch angle of the vehicle during and after the impact sequence should not exceed 75 degrees.
Occupant risk is also assessed by the response of a hypothetical, unrestrained front seat occupant whose motion relative to the occupant compartment is dependent on vehicular accelerations.
What is the MASH criteria for Post-Impact Vehicular Response?
Post-impact vehicular response is a measure of the potential of the vehicle to result in a secondary collision with other vehicles and/or fixed objects, thereby increasing the risk of injury to the occupants of the impacting vehicle and/or other vehicles. Excessive pocketing or snagging of the vehicle and the resulting post-impact trajectory, such as a high vehicular exit angle or spin-out of the vehicle, is not desirable.
