safety problems in car crashes
For many years the Allianz Zentrum für Technik (AZT) (Allianz Centre for Technology) has been committed to the safety of vehicle occupants. The need for wearing seatbelts, replacing them, restraining systems for children, benefits and risks of airbags, headrests and their proper adjustment are some of the topics which you are very likely to remember from Allianz automobile press conferences of past years.
This time round, in a series of scientific experiments which started in August 1996, we concerned ourselves with a certain group of vehicle occupants which, though they are generally referred to as “man’s best friend”, get the proverbial mother-in-law treatment – namely dogs. Unlike all other pets, which are only transported in vehicles on the odd occasion, the dog is a constant companion of humans wherever they go – hence also in cars.
However, cars are in no way designed for the needs of animals. It merely takes sharp cornering or sudden braking to cause a standing or sitting dog to lose his balance and slide from his place. In a collision the dog is exposed to basically the same risk as an unsecured child. The animal can be injured or killed and larger dogs, by their very weight, present a danger to human passengers. Being scratched or bitten by the frightened or injured animal is a further source of potential danger.
Dog breeders’ associations have classified more than 150 different breeds. Size and weight are of great importance when assessing safety in cars and these characteristics can vary in dogs as they do in humans, from the toddler to the adult stage. Yorkshire Terriers, weighing as little as 500 g and with a shoulder height of 15 cm, make up one end of the spectrum, Saint Bernards, weighing up to 85 kg and with a shoulder height of 90 cm, make up the other. One of the most frequent passengers is the German Shepherd weighing an average of approx. 40 kg.
Also very popular are smaller dogs, such as the miniature Schnauzer, Dachshund, and Terrier, ranging in weight between 5 – 13 kg. The bigger the dog, the more likely it is that he has a specific place in the car. Smaller dogs, by contrast, often tend to wander around in the car and can be a considerable distraction to the driver. This was borne out by a survey of 350 dog owners as part of the AZT research project. Owners of big dogs often possess a station wagon and use the loading area to transport their animal. In passenger cars the backseat has taken pride of place. Smaller dogs, on the other hand, seem to feel equally at home in all passenger seats and leg areas, finding the rear window shelf a particularly cosy place.
Safety devices for dogs are only seldom used in four or two-door sedans. 78% of dog owners transport their pet without any protective systems. Only very few mentioned transport boxes for small dogs and belts or protective grids for the heavyweights. The situation is somewhat better in the case of station wagons. After all, approximately 60% were fitted with a protective system, mainly nets or grids between the loading and passenger areas.
But how good are these safety systems – generally available in accessory shops or via mail order – when it comes to the crunch? This question has been scientifically investigated by the Allianz Zentrum für Technik in a series of 11 crash tests. On the one hand, a miniature Schnauzer, weighing 6.5 kg, was used to represent the segment of small dogs, on the other hand, a German Shepherd, weighing 40 kg, represented the segment of large dogs. Using a reinforced passenger compartment with two dummies secured with seatbelts in the front seats, frontal collisions at 46-47 km/h and a maximum carriage deceleration of 22 to 25 g were carried out.
The first crash test with an unsecured miniature Schnauzer on the rear window shelf showed the risk of fatal injuries to the animal: the small dog was hurled, passing the passengers and slamming with its back into the ceiling frame and finally head first into the windscreen. The strain, measured at more than 70 g, constituted forces of around half a ton.
At first glance a protective net seems to offer convincing advantages: as an all-purpose net it can easily be mounted at the B-column and at the seat close to the floor. It has no hard parts to it which could present a danger to animals or humans. We used such a protective net in our crash test, with the tiny Schnauzer again located on the rear window shelf. The high-speed film shots clearly illustrated that the dog, together with the protective net, was hurled against the windscreen. The mounting straps and their metal rings already gave way under slight strain. A peak load of more than 80 g at the point of impact confirms that the net absorbed virtually no energy. The only possible assessment: useless. Only in normal driving situations can such a net prevent a small dog from leaving the rear seat area and intruding on the occupants in the front.
A protective grid was mounted behind the front seats. This popular construction was fixed between the car’s floor and ceiling by means of adjustable vertical supports. The crash test clearly showed that this type of fixture may suffice for normal driving conditions. In the case of a serious accident, however, it is not even able to withstand the grid’s own weight. The protective grid already came loose before the dog crashed against it. After that it was only held in place by the front seats. Then, as a result of the impact which measured 23 g, the miniature Schnauzer bent apart the rods of the grid (force approx. 1.5 kN or 150 kg) partly tearing away his muzzle. Subsequently he was forced through the grid and hit the windscreen at no less than 43 g. As the forward movement of the grid coincided with the backward movement of the passenger dummy, the measurements displayed a top value of 70 g in the head of the dummy. The consequences in a real accident: considerable injuries to the driver or passenger, fatal injuries to the dog. Seeing that the all-purpose protective net as well as the grid already failed miserably in the case of the miniature Schnauzer, we dispensed with follow-up tests using a German Shepherd.
Dog safety belt:
A dog safety belt in the form of a harness was correctly attached to the three-point belt on the right side of the backseat. The tested product had no chance at all of retaining the 40 kg German Shepherd on impact. The seams already tore at a belt force of just under 2.2 kN, one tenth of what would be necessary to retain the dog. The animal severely deformed the backrest of the passenger seat and caused an enormous strain on the passenger dummy amounting to 156 g in the head and 51 g in the chest. The load limit of 80 g over 3 milliseconds, considered to be the bio-mechanical limit, was almost reached in the head of the passenger dummy. In a real accident this could have led to severe head injuries. Hence this restraint system, too, proved to be unsuitable, at least for larger dogs.
Plastic transport boxes for all types of pets have established themselves in international air travel. Transport box in station wagon – secured Secured in place under optimum conditions and – as is not possible in a sedan – supported by a massive steel bracket to prevent any forward sliding, this system passed the crash test without problems. Although the dog broke through part of the front wall of the box, it was forced back into the box as a result of the tension in the plastic. With a value of 77 g, however, the strain on the dog must be seen as critical.
Transport box in station wagon – unsecured:
It is also questionable whether the back supports in a normal station wagon – especially one with separate seats – are able to withstand such forces. To solve this question we carried out a crash test against a wall with a complete vehicle distinguished by its very stable backseat mounting. Since the automatic seat-belt mechanism is integrated in the back support, the connection between the back support and the C-column of the vehicle is constructed a lot stronger than in many other cars. In this instance, the back support withstood the impact of the crash, but broke apart at the separation level because the screws at the lower hinge sheared off. The peak load was recorded at 56 g. The plastic box used was similar in size to the dog transport box, but not identical in technical terms.
Transport box on the backseat:
Securely fixed to the two standard three-point automatic safety belts, whose buckle latches were connected through a massive screw, this arrangement gave a very solid impression at first sight. However, the dynamic crash forces lead to a slight submarining, so that the belts exerted asymmetrical pressure on the box causing it to virtually explode and disintegrate. Thus this form of retention must be categorised as unsuitable.
AZT Design study
Following the less-than-encouraging crash test results to date, the AZT engineers embarked upon a search for suitable anchoring points in the backseat area for a dog retention system.
Belt anchorage points are designed to withstand high forces and would offer a perfect means of mounting an additional restraint system. Unfortunately, in modern cars these points are well concealed so that they are not practical for additional installations. Only the safety belts themselves can be used for a restraint function. However, since the safety belt forces act relatively high above the seat area, an additional anchorage near the floor area is absolutely necessary.
To create both a universal fastening device, and one that does not restrict the usage of the backseat, we installed two adjustable safety belts at the anchoring points of the lap belt underneath the backseat in such a way, that the end bits stick out only a few centimetres from the seat’s front edge. These belts could now be used for a restraint system to absorb horizontal forces. In a first design study the protective grid, which had previously failed in the miniature Schnauzer test, was inserted into the anchoring points by means of its vertical support rods. In addition the three-point safety belts were hooked to the grid on both sides.
This anchoring system was then able to prove its effectiveness in a test crash using a 40 kg German Shepherd dummy in a laying down position. Even though the cross bracing of the protective grid was again unable to hold back the dummy, the overall construction remained perfectly in place this time.
New dog protection system
Based on the experience gained in this initial test, AZT designed the prototype of a new dog protection system aimed to combine the advantages of both a net and a rod construction, while eliminating the disadvantages of both systems. A net of large-surfaced safety belts to distribute the restraint forces on the dog over as wide an area as possible and to avoid dangerous concentrations at one point was spanned across a massive rectangular frame, held in place by two vertical supports similar to the protective grid described earlier. In the upper area the acceleration force was restrained by the two three-point automatic safety belts, and in the floor area, by the above described additional belts mounted at the anchoring points of the lap belts.
A first attempt with a circular frame of steel tubing, 20 mm in diameter and with a wall thickness of 2 mm, already achieved outstanding results in retaining the 40 kg German Shepherd dummy and exerting a load of only 25 g on the animal. Yet the deformation of the frame (statically more than 400 mm) was much too great. It would not be possible to avoid it from crashing into the front seats and thus endangering the occupants accordingly.
A reinforced frame of rectangular steel tubing, 30 x 30 mm and with a wall thickness of 3 mm, proved to be sufficiently stable and reliably held back the German Shepherd at a peak load of 63 g, without any contact being made with the front seats, let alone the driver or passenger. As a result of the large-surfaced support of the restraining forces on the entire body, the animal is not expected to sustain any injury. If an optimum belt with a bigger expansion capacity is chosen, the maximum load is likely to be reduced to under 50 g.
As you can see from the test that we have illustrated here, the steel frame was considerably deformed in spite of its strong construction. This clearly demonstrates the forces at work when a car is involved in a crash.
In a final graph I would like to again illustrate the basic concept of the animal restraint system for backseat use we have recommended. Two additional belts under the backseat create two anchoring points near the floor without hampering the normal use of the backseat space. A massive steel frame with a net of safety belts is simply inserted into these fastening points and spanned up to the ceiling with the usual clamping fixtures. This adequately ensures against rattling and shifting during normal driving conditions. In addition, the two three-point automatic belts are attached to lateral hooks via their buckle latches and thus, together with the lower anchoring points, they assume the enormous retention forces which in this test constituted 2.5 – 3 tons.
The model presented by AZT was not yet a finished product, but merely a prototype. It was meant to provide a stimulus to the manufacturers of protective systems for dogs, because, with the exception of a dog transport box optimally secured in the loading space of a station wagon, the AZT tests have shown the commercially available systems to be inadequate. Additional information 05/99: In the meantime the “Allianz Dog Protection System” is readily available as a production item. It is manufactured by:
Kleinmetall Post Box 1250 D-63519
Phone +49 6183 911200
Fax +49 6183 72152
The product is useable in 4-door sedans for the transport of dogs on the rear seat. While installed, it is not possible to carry passengers in the rear. Three sizes (S, M, L) with different width are available to fit most passenger cars, prized at about DEM 500.00 – DEM 600.00 (€ 250 – € 300).