Interview: Prof Norbert Schaub, Head of Testing Passive Safety, Vehicle Functions: "Crash tests will continue to be indispensable in future"

Sep 26, 2019
Stuttgart/Sindelfingen

As the head of testing operations for passive safety and vehicle functions, Norbert Schaub is also the overall project manager for the Technology Centre for Vehicle Safety (TFS). The issue of vehicle safety has always been dear to his heart. That is because after his apprenticeship as a mechanic at Daimler AG in Stuttgart, he worked as a paramedic for several years and helped many injured people after traffic accidents. After earning his degree in mechanical engineering, he returned to Daimler in 1986.

Mr Schaub, Mercedes-Benz is celebrating an anniversary in systematic crash testing this autumn. Do you have a general idea of how many crash tests have been conducted since 1959?

Schaub: We did a little bit of research in our archive on the occasion of the milestone anniversary. Between the opening of the first crash test building of Mercedes-Benz in 1973 and September 2019, there were 13,357 crash tests in all. In addition, there were 698 of them in the period from 1959 to 1973 – which adds up to a total of over 14,000 crash tests with complete vehicles. Plus there was a host of component tests and crash tests that we outsourced.

A proud number. However, it is probably not possible to quantify how many Mercedes-Benz drivers owe their lives to this systematic accident simulation, because they happened to be in a traffic accident in a vehicle with above average safety, is it?

No. But our colleagues from Accident Research who analyse real-life accidents show us pictures of serious accidents on a regular basis. Even we safety experts are then impressed how minor the injuries of the occupants of a modern Mercedes-Benz in collisions from high speeds can be. And often we also receive thank-you letters from our customers.

How many crash tests does Mercedes-Benz conduct annually at present?

Our goal for 2019 is to conduct 900 tests with complete vehicles. We opened our new crash test centre in November 2016, the Technology Centre for Vehicle Safety (TFS), and shut down the old crash building in February 2017. We have been ramping up the number of crash tests in the TFS continuously since then. The capacity limit is around 900 to 1000 crash tests a year. We are now also conducting truck crash tests in-house.

What could the old facility not do that has now become possible?

The TFS allows us to tailor crash tests even more closely to reality. Apart from the capacity limitations of the old facility, the simulation of accidents at junctions, car-to-car tests in linear traffic with higher masses and speeds, the influence of PRE-SAFE® and assistance systems in the immediate pre-accident phase as well as the testing of vehicles with alternative powertrains were the major reasons for a new building.

How many different crash test configurations are demanded by law in the various countries?

Legislation is not the only driver when it comes to the number of crash scenarios. The stringency and number of requirements are nowadays greatly determined by the rating institutes. For example, Euro NCAP is planning a test for 2020 that will see two moving vehicles collide: the test car and a standardised vehicle with a deformable barrier will approach each other at a speed of 50 km/h each ("car-to-barrier test"). Furthermore, there are internal Mercedes-Benz requirements derived from our in-house accident research findings from the examination of real accidents. All in all, the development aim for us as a global manufacturer is around 40 different load scenarios for our vehicles.

How many cars are actually crashed for the development of a new vehicle?

Around 150 real crash tests are currently carried out for a vehicle model series. In some cases, the vehicles, and especially prototypes, are used several times. For derivatives, i.e. models derived from the base model, the similarity to the base vehicle means that not quite as many crash tests are required. Up to 100 overall-vehicle crash tests are often sufficient here.

Do we even need the classic crash test in future at all? For one, computer simulation has also become more significant in this area. And for another, modern cars today have a host of assistance systems that help to prevent accidents. And maybe we will already be driving in autonomous mode in the very near future …

Fewer accidents does not mean no accidents. It is true, the comprehensive approach to our safety philosophy is about preventing accidents. Where this proves unsuccessful, the aim is to mitigate the consequences of an accident. This is where passive safety continues to be important, maintaining an intact passenger compartment and providing the best possible occupant protection by means of restraint systems. A safe vehicle uses all possible means of preventing accidents, but is always prepared for the eventuality of an accident. Accordingly, all future vehicles, including automated vehicles, also must meet our high requirements on crash safety. Crash tests will therefore continue to be indispensable in future.

Let us stick with the mobility of the future for a little longer. There are already vehicles driving autonomously in the TFS, are there not?

Yes, but this involves how the test vehicles are powered. Conventionally, a towing cable accelerates the vehicle to be tested. However, the drawback is that the kinematics are not exactly like those in a real accident, because the body dive during braking is missing. That is why the TFS for the first time allows conducting crash tests in which the vehicles can drive to the obstacle on their own power. That is to say, independent of a towing system or a driving robot, which would take up the seat of the dummy at the wheel. Following the braked straight-line driving, which we currently conduct autonomously at speeds of up to 70 km/h, the next stages of autonomously driving crash test vehicles are cornering manoeuvres and car-to-car tests. We are working on tailoring the crash test in the building even more closely to what happens in real accidents. At the same time, we are also in the process of validating the sensor/radar suitability in the TFS in order to be able to simulate autonomously driving cars.

The TFS is surely also designed to crash cars with electric drive?

Of course. Mercedes-Benz always applies the same high safety standards to all its vehicles. This is true for both vehicles with a conventional internal combustion engine and those with an alternative powertrain. For vehicles with high-voltage systems, there are essentially three new challenges that must be considered for accident safety: structural safety, high-voltage safety and fire safety. Apart from their high level of conceptual safety by virtue of a protected installation position, our high-voltage batteries also have a high level of inherent safety verified by additional, in-house safety specifications that exceed established standards. The TFS offers new test constellations to verify the safety of the batteries. In addition to crash tests with complete vehicles, we also conduct component tests on deceleration sleds. The aim is to ensure that the inner workings of the batteries must not lead to critical cell damage even under fast acceleration.

Electric cars provide locally emission-free driving. But what about the sustainability of the TFS?

One of the energy-related highlights is that the building is heated by the waste heat from the adjacent climate/wind tunnel. This saves up to 70% of the energy normally required to heat the building. Other examples include the LED lighting concept at the crash locations and in the offices, or the heat exchangers that draw heat from the waste air and preheat the fresh air. And let's not forget: the TFS has a green roof.

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