An opinion on the biomechanics
of trauma

The subject of this statement is a discussion about the usefulness of a Front Brake Light on vehicles held on 1st March 2018 at Berlin Tegel Airport


Field study to test a Front Brake Light at Tegel Airport (University of Bonn January 2018)

A. Question

  1. In theory, would it be expected that, in a relevant number of crash victims with traumatic brain injury or cervical spine injuries, these injuries would have been less severe or could have been avoided altogether if the victims had received advanced warning of the impact and could have taken some action to mitigate its effect?
  1. If the answer to Q1 is positive, then:

How many crash victims suffer traumatic brain injury or cervical spine injuries? What is the economic cost of these injuries to the nation?

Is it possible to make some approximation as to how many minor injuries could have been avoided altogether, and how many moderate injuries could have re- sulted in less serious injuries?

Is it possible to estimate the resultant cost savings? (In addition, there is always the emotional benefit to those affected from reducing the severity of the injuries.)

  1. What effect would the advance warning of an impact have upon vehicle occu- pants? Can it be hypothesised that the warning and an increased preparedness (e.g. adopting the brace position, stiffening of neck muscles, etc.) can alleviate the resultant injuries such as cervical spine trauma? One could imagine the dif- ference between a body thrown back and forth by the impact, because it is un- restrained, and one that has braced itself and, therefore, is less likely, at least in theory, to be flipped back and forth.

Dr. med. Wolfram Hell

B. Opinion

Question 1:

In principle, at least, it can be assumed that, if the crash victim has prior warning, the severity of the crash will be reduced or the crash could even be avoided completely. Typically, however, the pedestrians who are involved in crashes with cars or trucks are either children (1-12 years) or older citizens (> 65 years, often > 80 years). Such pedes- trians are best influenced by active emergency braking systems coupled with pedestrian detection day and night.

The Front Brake Light is most likely to be effective for pedestrians aged 13-64 years.

Title of graph

Distribution of pedestrian crashes, population and risk of crash involvement by age group

Fig. 1: Pedestrian age, population and risk of crash involvement

An earlier evaluation by my cooperation partner ADAC UFO revealed the following main injury factors: the head, thorax, abdomen, spinal column and pelvis are particularly at risk of life-threatening injuries. Logically, the severity of the injury to the pedestrian is proportional to the impact velocity and the kinematics of the impact.

The lighting conditions can also be crucial, as many pedestrian crashes happen in darkness on unlit roads.

Fig. 2: Patterns of injury to pedestrians in ADAC Accident Research (2013)

Thus, in principle, it can be assumed that the effect of a Front Brake Light, would be positive. The size of the effect would have to be calculated from data obtained from ana-lyses of both real crashes and reconstructed or simulated crashes. However, this positive effect would have to be substantiated theoretically and empirically quantified by accident reconstruction.

In the future, in principle, autonomous self-braking systems will also recognize a green light and thus the braking or non-braking of the oncoming vehicle. In principle, such sys- tems should also reduce bicycle and pedestrian crashes.

Question 2:

In principle, a retrospective study of real pedestrian crashes can shed light on pre- defined questions. There are several databases.

  • Pedestrian fatal crashes (major crashes from the database of LMU)
  • Pedestrian crashes with serious injuries from the ADAC Accident Research da- tabase

The crash data should be differentiated according to whether the impact was with a car or a truck, van or bus.

An approximation of the economic costs of the crash is also possible. A detailed evalua- tion using the so-called ICS (Injury Cost Scale) is only just beginning.

Depending on the depth of the evaluation, further statements may be possible, for ex- ample, a reduction in minor pedestrian crashes.

More likely, it will become possible to classify such crashes as: Preventable, partially avoidable, and unavoidable.


European standards have a long lead-in time (up to 20 years). Technical pro- gress, especially in the transition to automated driving, is much faster, which is why opinion-makers and consumer testers are particularly relevant in Sweden, England, Switzerland, the Netherlands, Austria and Germany. In these countries, a public relations offensive should be mounted. Innovations in Sweden are often copied by other countries with a time lag of about 5-10 years.

Question 3:

The car occupants would be forewarned that an uncontrolled or late braking vehicle is approaching them. Results from international research studies suggest that forewarning has a positive effect. For example, unprepared passengers have a higher injury severity than informed and thus muscular-tensed drivers. Even evasive movements can be bet- ter planned by the driver or, in the future, by automatic driving systems.

If an out-of-control truck threatens the end of a line of stationary traffic, the threatened driver may also initiate an evasive movement. So-called spinal cord injuries occur in approximately 50-70% of all car crashes involving injured persons. Here, an advance warning, which was tested in volunteer tests on the test sled, also has a positive injury- reducing or avoidance effect.

In Germany, the annual cost of the estimated 200,000 cases of cervical spine injuries resulting from road crashes amounts to around 500 million Euros annually.

A reduction by, for example, 10% would therefore have a significant effect. Likewise, in the case of even more serious injuries, (AIS 2+) a more substantial cost saving could be expected.

For the next decade (2020 – 2030), the EU is particularly targeting the reduction of seri- ous injuries. Modern pre-safe systems (for example, Mercedes Benz) already have all- round monitoring (front, side, rear). By coupling these sensors with a sensor to detect the Front Brake Light, these systems could coordinate their evasive movements more effectively.

Truck / Bus / Van

Fig. 3: Mercedes S class sensors (Daimler)

Fig. 4: Mercedes S Class Pre Safe Plus (Daimler)

PRE-SAFE: Activation of the front belt tensioners due to radar signals

unavoidable crossing accident
Activation of the PRE-SAFE© belt tensioners based on the information of the radar at close range

unavoidable collision with oncoming traffic
Activation of the PRE-SAFE© belt tensioners based on the information of the radar at close range

Fig. 5: Mercedes S Class Pre Safe (Daimler)

Fig. 6: Injury kinematics car occupant front, rear, side collision (Kodsi Forensic Engineering USA)

Frontal and side collisions in particular have a high risk of injury even for occupants pro- tected by seatbelts and airbags. In the case of rear-end collisions, it mainly results in cervical spurs that are not life-threatening (AIS 1 injury severity) but very common (50- 70% of all car collisions) and 10% of so-called long-term cases (resulting in more than 6 weeks occupational disability). Accordingly, the effect of a Front Brake Light and its po- tential for injury prevention should also be scrutinised in detail on the basis of real road crashes.

KilledTotal InjuredSeriously injuredSlightly injured

Fig. 7: Traffic injury statistics Germany 1991–2016

The proportion of seriously injured persons (i. e. admitted to intensive care units) has remained constant for about five years, with a cautious annual estimate of approxi- mately 10,000 cases in Germany. A differentiated consideration regarding the effective- ness of a Front Brake Light seems to be indicated here, possibly also with the use of traffic simulation models.

It may be concluded that a full investigation into the potential effectiveness of a Front Brake Light would benefit from analyses of data from both traffic simulation models and real-world crashes.


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  2. Unger, T.: Unfälle mit Fußgängern , ADAC Unfallforschung (2013)
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  8. Widder, Bernhard et al.: Beurteilung der Kausalität bei gutachtlich wichtigen Krank- heitsbildern, HWS-Beschleunigungsverletzungen

Referenz-Reihe Neurologie: Methoden: Begutachtung in der Neurologie DOI: 10.1055/b-0034-20112 (2011)

This statement has been prepared to the best of my knowledge and belief.

Dr. med. Wolfram Hell, Traumabiomechanics