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Life insurance for the driver

Crash and impact testing for safety

What is the optimum structural strength of the cab? Where should it be rigid

and where should it be designed to yield?

How should a seat belt be attached for maximum safety? How should it

lock?

What is the role of the seat and the seat base? When should seat belt ten-

sioners or airbags release?

When should the safety systems remain passive to allow the driver to drive

safely to a standstill? 

Questions like these constantly engage Scania's safety engineers and cab designers. Often the only viable testing method is full-scale trials.

Research on safety systems and features is a continuous process. Scania's road safety team addresses new findings and demands on a constant basis to give drivers and operators access to state-of-the-art safety technology as quickly as possible.

Crash and impact tests, as well as tests on driver protection systems, are an integrated part of Scania's cab development. In some cases the cab must offer maximum impact protection, yet it sometimes has to yield to reduce the forces on the occupants.

The same applies to the driver restraint systems. Sometimes they enter fully into action at once, offering maximum protection. At times they should instead allow the driver to remain in full control of the vehicle until it has stopped in a safe place.

The aim of Scania's crash and impact testing is to continuously develop the protection systems incorporated in the cab and to safeguard the interplay between active and passive safety features and systems.

Testing seats and integrated seat belts

Scania found already in the mid-1980s that integrated seat belts offer the best protection for the driver - they are more comfortable to wear and thus more likely to be worn. When they were introduced in 1988, the belts themselves, as well as the seats, their attachments and the cab floor had been subjected to extensive sleigh testing by Scania to fully assess what happens during an impact in a Scania cab.

As a result, the cab floor was reinforced. The seat base was designed to yield slightly when the belt had taken up its slack to reduce the g-forces on the occupant.

Integrated seat belts are standard on the 4-series in Europe. The new luxury seat has a sophisticated design, where the belt is fully enclosed in the backrest and the shoulder strap adjusts automatically to suit the height of the occupant.

Engineering belt tensioners and a driver's airbag for a truck

The accident sequence in a truck differs a great deal from that in a passenger car. Everything is slower because of the weight of the vehicle, but the ultimate forces can be very high because of the momentum involved.

Great care must therefore be taken to ensure that car-like systems like belt tensioners and airbags are fully adapted for the type of protection required in a truck cab.

Destructive testing

Scania has carried out a large number of crash tests on 4-series cabs to determine the precise triggering point for the g-sensor that activates the belt tensioners and the airbag when fitted.

All experiments start with computer simulations at Scania's Technical Centre. When satisfied with the results, the engineers proceed to full-scale testing on trucks. Preparations are meticulous because every test is destructive.

To trigger or not

Provided that the driver or passenger is belted, Scania's integrated seat belts offer a high level of protection. In many cases there is no need for the tensioners to enter into action or for the airbag to deploy:

When the truck hits a flat barrier at 15 km/h? - No. The integrated seat belt pro-

vides good protection.

When the truck hits a 200 mm kerbstone at 50 km/h? -– No. The suspension com-

ponents are designed to cope with such an impact. It is thus safer for the driver to

be able to steer afterwards.

When the truck hits a lightpost at 50 km/h? - No. The mass of a lightpost is small

in relation to the truck. The cab structure takes care of the blow and the driver can

steer and brake to a safe halt.

When the truck is hit by a car doing 57 km/h? - No. The impact takes place low in

the front and the truck driver is in a safely high position. The front of the truck is

designed to protect the steering and brake components to allow the truck driver to drive to

a standstill.

On the other hand, in a severe impact, all the safety systems available should be

used to protect the driver. The g-force sensor should therefore trigger the belt ten-

sioners and the airbag in the following cases:

When the truck runs into a flat concrete barrier? - Yes. From around 25 km/h

driver protection benefits from the belts being tensioned.

When the truck hits the back of a trailer? - Yes. The impact area may be fairly

small - for example if the truck hits a platform trailer - with a risk of some intru-

sion in the foot and knee area. The sensor triggers to hold back the occupant

from around 25 km/h.

Crashes with cars

Trucks are required by law to have underrun protection at the rear in most countries and at the sides in some countries. Scania can increasingly offer such equipment ex-factory on the 4-series.

Front underrun protecting devices are currently discussed within the EU. How should they be designed to offer maximum protection for colliding passenger cars?

The reasoning is that the car occupants are best protected if the crumple zone of the car is made to work to its full potential. The truck's underrun protection should go so far down as to hit the car on the bumper, not higher. All the protective structures in the car are then used to the full.

Meanwhile, Scania has designed the aerodynamic front bumper on the 4-series to act as a full underrun protection bar. The design is more resilient than stipulated in the proposed EU-directive. Scania can easily adapt this design to the regulations, should the legislator settle for a stiffer structure, and we can add bars suitable for other chassis heights.

Scania has found the more supple design to work better, because more of the deformation takes place on the truck, reducing the g-forces in the car. In one test, a Saab car crashed into a 4-series truck at 57 km/h. The whole crumple zone of the car was used, but the passenger compartment was intact and the occupants would have survived.

Swedish cab safety standard the minimum

The momentum of a heavily laden vehicle in motion is very high and so are the forces involved if something happens, for example a roll-over accident, a head-on crash or shifting cargo. Research to reduce these risks for truck drivers resulted in the Swedish cab safety standard, which was adopted already in the 1960s.

To conform to this standard, the cab has to pass a three-stage test. The cab must support a 15-tonne weight placed on the roof. A 1.5-tonne pendulum weight is then swung from 3 metres against the driver’s A-pillar at windscreen level and the rear cab wall is subjected to a similar blow. After these tests, the driver’s door must remain closed. Sufficient survival space should remain for the driver.

Scania regards the demands of the Swedish cab safety standard as the very minimum level for its truck cabs. The driver is entitled to good protection, both in a crash, if the vehicle turns over or if the load shifts forward.

Since the early 1980s Scania cabs are manufactured from hot-dip galvanised steel to retain their structural strength over a long period.