Comments: MASH Style Underride Guard Crash Tests

I am commenting as an American underrun victim/survivor and international  truck safety activist. I am a truck underride survivor so will be commenting on Vision Zero and Safe System, TUBS (Truck Underrun Barriers), and truck or trailer  mounted attenuators. I am also interested in safe and forgiving roadsides  and the types  of roadways and speeds involved in rear underrun truck crashes as these are all inter-related. There is strong support of these Vision Zero or Safe System holistic approaches to highway safety, you cannot separate the roadway and road hardware and rules from underrun guard design and effective use. We must move the formulation of roadway safety systems from political frameworks to roadway and vehicle engineering  science collaborations. It is long overdue for the U.S. and Europe to also join the modern age and incorporate truck underride guard testing into the MASH testing system.

“In a Safe System, if a road user travels in accordance with all traffic laws and on a safe road in a safe vehicle, but finds through no fault of their own they become involved in a crash, the crash should not result in death or serious injury. Similarly, if a driver does make an error then a Safe System should react to minimize the consequences of the error. In a Safe System, the regulatory system should strongly discourage socially unacceptable road use behavior. Thus all road user training and behavior  management, vehicle development and regulation, and road design and traffic  management systems should be considered as a holistic inter-related system and  governed according to this paradigm.

The Safe System comprises four major  interconnected elements: safe use, safe roads and roadsides, safe vehicles and safe speeds.” We believe Vision Zero based systems will be the norm around the world and are already taking hold in the U.S., better late than never. We believe this integrated holistic approach improves safety outcomes and moves us to a forever improving  system of on-vehicle crash testing such as used in the MASH system in the  U.S. where we can integrate NCAP type testing of underrun barriers. Testing of on-vehicle rear underrun guards at IIHS showed that failed tests accelerate improvement of safety technology, those that passed tests will not be improved as the need for  improvement is not shown to the public. Real world crash tests at speeds beyond safety equipment’s easily achievable capability provide ongoing public pressure for improvement such as NCAP testing has shown for cars.

The FHWA Office of Safety considers that a 100 km/h (62.2 mph) crash test is representative of worst case run-off-road crashes. If we test at real-world crash speeds we will get underride protection that performs at these speeds. Crash attenuators tested  at 100 km/h (62.2 mph) perform beyond 70 mph. We must incorporate real-world crash speeds and higher-speed roadways to our testing equation, if we fail to relate roadway types and crash speeds we end up testing for success of hardware rather than to meet real-world needs. Low-speed crash tests do not test for real-world needs.

We believe extending guards from the truck or trailer rear planes will become the norm due to energy-saving boat tails on trailers that extend beyond the trailers to save fuel. Extending underrun guards to increase available stroke distance to absorb more crash energy at higher-speeds will make practical and economic sense. Moving guards away from the truck body plane by 500 mm or more  increases effective crash speed to our recommended 100km/h (62.2 mph) for high-speed crash tests. The added stroke distance for underride guards is an easy solution for higher-speed guards and high-speed public testing would encourage quick designs and working solutions through increased public pressure due to failure of guards in higher-speed testing. Major truck and trailer manufacturers have used this extended guard equation in their future guard designs for 40 plus years.

“The size of an energy-absorbing truck front structure directly correlates to the survivable closing speed between car and truck in head-on collisions (e.g. 75 km/h (46  mph) survivable closing-speed requires a 400 mm long energy-absorbing structure, 90  km/h (56 mph), requires 800 mm (2.6 feet)).” From Volvo Report


Chalmers Car-to-Truck Frontal Crash Compatibility

Increasing the length of the HC (Honeycomb shaped front nose underrun guard)  increases the critical impact speed

To 95 km/h (59 mph) with a 300 mm – length HC structure (+27%)
To 102 km/h (63 mph) with a 600 mm – length HC structure (+36%)
To 107 km/h (67 mph) with a 900 mm – length HC structure (+43%)


Crash testing for failure rather than using low-speed crash testing to provide easy success will encourage rapid improvements in safety design of guards. Increasing roadside hardware energy-absorption and providing wide forgiving roadsides all improve  safety as an holistic inter-related system. Crash types such as parked roadside crashes require multiple improvements. NCAP type testing will provide visual safety information to an usually technically poorly informed public, sales pressure will speed technical improvements. Instituting underrun guards into MASH type testing regime will speed world adoption of these improved crash testing systems and save lives around the world.

The Underride Network supports a similar criteria for underride guard crash tests as those submitted by Prof. Raphael Grzebieta and (Adj) Associate Professor George Rechnitzer and Transport and Road Safety (TARS) Research Centre in Australia based on the criteria used for MASH crash tests in the AASHTO Manual. We would submit requiring multiple speed tests to include real-world crash speeds and would not limit extension of guards to increase crush or stroke distance to increase guards effective speed while diminishing deceleration forces. Tests might be performed at 44 mph and 50 mph and 62.2 mph to test minimally compliant guards in low-speed tests and using higher speed tests to monitor performance at real-world crash speeds. We support testing for Practical Worst Case (PWC) scenario crashes that happen in the real-world just as MASH includes PWC in it’s crash test series. We must include tests of offset controlled after crash direction of vehicle spin or VRU (Vulnerable Road User or bikes and pedestrians) after crash spin to assess high-speed crash avoidance for cars and prevention of running over VRU users in frontal crashes. John E. Tomassoni “It is expected that certain offset conditions could result in car rotation such that the passenger compartment may beneficially avoid intrusion entirely”. WE would encourage annual NCAP type testing of truck and trailer underride guards to encourage industry improvement of guards on an annual basis such as crash performance of cars improves on an annual basis using publication of the results of NCAP tests for cars to increase sales of better performing products.

When we crash test underride guards at 30 to 35 mph for 50 years we get underride guards effective to 30 to 35 mph for 50 years! We must crash test guards at real-world speeds that we might see on highways 100 kph (62.2 mph) and then through public pressure we will see guards designed to protect the public at 62 mph and above!



%d bloggers like this: