REAL LIFE IS FOUNDATION OF SAAB 9-5 SAFETY
Real-life Safety Approach Creates Safest Saab Ever Built
NORCROSS, Ga. - Saab engineers have always regarded occupant safety as one of a car's most important design features, starting with the first Saab prototype, unveiled in 1947. Since then, the Saab safety engineers have worked with the objective of setting even higher safety standards with each new generation Saab. Innovative new safety systems, "Real-life Safety" engineering and an extremely rigid body structure contribute toward achieving this objective-the Saab 9-5 is the safest production Saab built to date. The core of Saab's Real-life Safety approach to designing cars is that the cars must be as safe as possible in accident situations that occur in the real world. Since 1972 Saab has investigated more than 5,000 accidents involving Saabs in Sweden. Data from these investigations provide the starting point when designing new Saab models. In addition to providing invaluable information regarding the real-life crash safety properties of Saab cars, this data also helps Saab engineers perform more real-life like crash tests. The Saab 9-5 has been subjected to more than 40 different crash test configurations, including car-to-car, car-to-truck and car-to-dummy-moose. Of these, only 11 are mandated by government standards.
Front and Rear Triple Load Paths on Each Side
The front and rear structures of the new Saab 9-5 incorporate three robust, interconnected load paths on each side that optimize and distribute crash loads according to a predetermined pattern. Saab uses a unique patented "horseshoe" shape for the front beam structure of the car, which effectively eliminates localized high stresses, reducing the intensity of the penetration and increasing the time before the crash pulse reaches the cabin. The longer this delay, the less the magnitude of the forces on the occupants. The less crash energy allowed into the cabin, the more the seat belts can restrain their wearers and reduce the contact speed with the inflated airbag cushion. This "horseshoe" shape also helps spread energy loads during angled impacts and reduces the risk for a ramming effect that can occur with a "forklift" shaped front end commonly used in other carmakers' designs. A "forklift" shaped front end absorbs energy less efficiently, and can cause unnecessary damage to the oncoming vehicle. At the front of the Saab 9-5, the primary load path is formed by the exceptionally wide and long longitudinal side members that form the front sections of the body frame. The second path transmits loads at a higher level via the wheel-arch reinforcements to the A-pillars at waistline height where the structure is heavily reinforced to carry the main door hinges. The third path, which runs at a lower level, uses the new front sub-frame to direct additional crash forces to the lower part of the safety cage via its reinforced and widely spaced mounting points. "Although it is impossible to predict what type of crash you will have in a frontal impact before it happens," says Mats F‰gerhag, manager of the Saab's crash safety center, "we can at least predict how the front structure will deform. The more load paths between the point of contact and the rigid safety cage behind it, the easier it is to absorb the energy of the impact." The safety cage itself is an extremely rigid system of steel members that pass around and over the front and rear seats. The parts likely to be subjected to the highest forces are reinforced by high-tensile steel with extra metal thickness and all the joints are carefully designed to resist tearing. The total body structure includes many innovative details, and patents are pending on eight specific features.
Five Progressive Frontal Deformation Zones
The front structure works in an integrated way to absorb and distribute crash forces. By directing about 50 percent of the crash energy through the main central member and 25 percent each to the upper and lower members, the front structure of the new Saab 9-5 behaves in the same way in car-to-car crashes as against a barrier, which is not the case for most other makes. The more effectively energy can be absorbed in the collapsible zone, the more intact the survival space in the safety cage becomes. Even when the car hits a tree or pole in the center of the widely spaced side members, the front beam resists the impact by applying bending loads to the other members. The system is engineered to deform in a predetermined manner, in five progressive stages according to speed and severity of the particular impact. The five stages of energy absorption operate at the following approximate speeds: 0-5 mph: The self-repairing molded plastic bumpers absorb low speed impacts and normally need no repairs. 5-10/12 mph: The crash boxes behind the bumpers absorb forces of a collision up to 12 mph without further damage to the front and rear structures. Body damage is minimal. 10-20 mph: At higher impact speeds, the load boxes behind take progressively more of the total crash energy, collapsing in a controlled way so relatively little damage is caused to the body structure. 20-40 mph: The total system starts to work, dispersing and absorbing the crash energy through all three load paths, resulting in virtually no deformation of the safety cage. Above 40 mph: At high speeds, the total car starts to be deformed. Even the safety cage helps to distribute the energy away from the occupants, by working to absorb the higher energy levels involved and deforming in a predetermined way. All the speeds mentioned above relate to impacts against solid immovable objects. When other vehicles are involved, the intensity of the crash forces is usually about half the level of the forces generated at the same speed against a barrier. Accidents involving actual impacts against rigid objects at speeds above 40 mph (equivalent to about 80 mph car to car) are extremely rare.
Outstanding Rear and Side Impact Protection
The Real Life Safety philosophy has also been applied to the development of the Saab 9-5's side and rear structures. The rear body provides an outstanding level of crash protection, thanks to the same kind of collapsible elements and reinforcements as at the front. A shield around the fuel filler neck is designed to protect it from breaking away, while the tank itself is in the safest possible place, ahead of the rear axle. In the event of side impact, only very limited deformation zones are available for absorbing the crash energy. The body structure is designed mainly to distribute the impact forces over as large an area as possible. The crash energy is absorbed by the side of the car, where the door pillar is made of high-strength steel, and the reinforcements in the sill and door pillar assist in distributing the impact forces to the safety cage surrounding the interior. The door pillar of the Saab 9-5 is designed to behave as a pendulum in the event of a side collision. The center section of the pillar is very stiff to prevent the pillar from deforming and intruding into the interior. The top part of the door pillar performs as a "hinge" and retains its position when the remainder of the pillar is displaced inwards like a pendulum. As a result, it is the most robust parts of the human body (the pelvis area) that will be subjected to most of the crash energy. This reduces the risk of injury to the most sensitive parts of the body - the rib cage, head and chest. Cross-members in the floor under the front and rear seats are designed to prevent the Saab 9-5's body from being compressed sideways and help distribute side impact forces into more of the safety cage structure.
World-First: Saab Active Head Restraint (SAHR)
Real life accident statistics show that neck injuries are one of the most common results of rear-end collisions, even at relatively low speeds. The triggering factor in these whiplash injuries is the violent movement of the head in relation to the body during an impact from behind, often leaving victims with long-term injury and pain. In the event of a rear-end collision, the SAHR system effectively limits the head movement of the occupant during the impact. The Saab Active Head Restraint (SAHR), introduced as a world-first innovation in the Saab 9-5, effectively reduces movements of the occupant's head following a rear end impact and reduces the risk of whiplash injuries. The SAHR system is standard on all 1999 Saab 9-5 and Saab 9-3 models. The system is entirely mechanical and is based on the lever principle. An upper padded support is connected to a pressure plate in the backrest of the seat. In some rear collisions, the occupant's body will be forced by the crash pulse into the backrest, which moves the pressure plate towards the rear. Subsequently, the head restraint is moved up and forward to "catch" the occupant's head before the dangerous whiplash movement can start. The new system is designed to come into operation in rear-end collisions starting at speeds equivalent to a barrier impact of about 10 mph. The precise activation of the system is determined by the force with which the occupant's back is forced against the backrest, the magnitude of the collision forces and by the occupant's weight. The SAHR's performance is always optimized automatically to match the occupant in the seat at the time and conditions of the crash. Another major benefit of the mechanical SAHR system is that in most accidents it needs no repairs to restore it to operational condition after it has been activated, unlike pyrotechnic systems (including airbags). After the head restraint has constrained the movement of the neck, it reverts to its initial position and is immediately ready to operate again. As whiplash injuries usually occur in low-speed collisions in which the car may sustain only limited damage, the active head restraint does not increase the cost of the repairs needed after the crash.
Head and Torso Side Airbags for Added Side Impact Protection
As further protection in the event of a side impact, front seat head and torso protecting side airbags are included as standard equipment on all Saab cars. Located in the outside bolster of each front seatback, to be correctly positioned regardless of the occupant's seat position, the side airbags have an air volume of 25 liters and are divided into upper and lower sections. When activated, the airbag inflates in two stages. The bottom section of the bag is inflated first to protect the torso, which is the first part of the occupant's body at risk from side-impact collision forces. While the lower section of the bag is fully inflated, the upper section of the bag is gradually inflated. The top section of the airbag then fully inflates, with the assistance of pressure from the lower section allowed through check valves when the occupants' torso contacts the lower bag area, to offer protection for the head. The entire process takes only a split second. The crash sensor triggers the gas inflator in the airbag five milliseconds (0.005 seconds) after the crash process has started. The lower part of the airbag is filled after 15 milliseconds, and the top part after 30 milliseconds. When developing the side impact protection of the Saab 9-5, Saab safety engineers used the Biofidelity Side Impact Dummy (known as the BioSID), the most sophisticated dummy available. Compared to the type of dummy stipulated by various regulatory standards around the world, BioSID has a larger number of measurement points and senses the sequence of events in a way that better simulates the way the human body reacts. In total, Saab utilizes 33 various dummies, of which BioSID is only one, ranging in size from 17 - 223 lbs. in performing crash tests on its vehicles. Two fullsize front airbags are standard on all variants of the Saab 9-5. A 60-liter driver airbag is built into the center of the steering wheel, while the 120-liter airbag for the passenger side is mounted in the dashboard above the glove compartment. Both airbags are optimized for a belted driver and passenger.
New, Force-Reducing Front Seat Belt Pre-Tensioning System
All five seating positions incorporate three-point inertia reel seat belts with semi-automatic height adjustments and anti-submarining ramps to prevent the occupant from sliding under the belt in a severe frontal collision. All Saab 9-5 models are now fitted with a new, force-reducing front seat-belt and pre-tensioner system which is more effective and more comfortable. These new seat-belts feature more pliancy which, at a predetermined load level, causes the belt to slacken slightly when the occupant is thrown forward with sufficient force. This permits gentler restraint of the forward motion of the occupant, and reduces the risk of belt-induced injury in the event of a high-speed collision, especially if the individual involved has frail bones. It is nevertheless worth noting that any possible belt-induced injuries would be marginal compared with the injuries that are likely to be sustained by an unbelted individual in a corresponding collision. To help protect the occupants in rear impacts, the seat belt pre-tensioners are also activated in a rear-end crash. Two foldable rear head restraints are standard, while a third, center headrest is available as an accessory.
Cockpit Layout and Chassis Design Contributes to Driver Control
Saab's extensive Real-life Safety research and subsequent active-safety engineering has two primary objectives - to design the driver's environment so that the driver will find it easier to avoid incidents, and to provide the car with the properties needed to enable the driver to avoid accidents in emergency situations. The chassis of the Saab 9-5 is designed and tuned to ensure the best possible road safety by following these guidelines:
The design of the Saab 9-5 follows this safety philosophy. The car has good steering precision and directional stability, it has consistent and stable behavior on braking and acceleration, and it also retains its poise in sudden maneuvers on a variety of road surfaces. All of this ensures that the driver will always be in full control of the car.