Vehicle Safety Systems

What's New For 1998, ‘99?
by Bob Brown

In 1995, Volvo introduced the first side impact airbag to the American car buyer. They were driven by the desire to go to the next level in crash survivability, since front airbag technology has proven its benefits to the properly seated and restrained vehicle occupants. Apparently this desire for increased safety is contagious, as 18 manufacturers introduced side airbags in over 46 models to the American market in 1998, either as standard equipment or optional. This is a good time to review what the side impact airbag and other safety developments mean to the emergency rescue personnel involved in extrication of car crash occupants.

First, let’s look at the two basic styles of side impact airbags. The first, and most common style, is known as the seat mounted side airbag. This bag is located in the outboard, or door side, of the seat and inflates through the seam of the seat during side impact. Protection is offered for the mid to upper torso area, cushioning the occupant from impact with the door panel and providing some protection against impact with the side glass. The Ford head/thorax bag, new for ’99, extends far enough above the windowsill to provide head protection. The Volvo system, it should be noted, is manually activated. Disconnection of the battery does not affect this system, and consequently Volvo has produced a written guideline for disabling their side impact airbags. All other side impact airbags are electronically fired, and Volvo has announced electrically activated side bags for the ’99 S80.

An advantage of the seat-mounted side impact airbag is that it can be smaller since it moves with the occupant as the seat is adjusted forward or backward.

The second style is mounted in the door, typically installed in the rear half area. This bag deploys through a seam in the door panel and provides coverage for mid to upper torso, with some providing additional protection for the head.

It should be noted that these systems deploy at a much greater speed than the front impact bags, since there is so little space between the occupant and the exterior of the door. Since both types of side impact airbags reduce head and torso injury measures, the emergency responder can expect an overall reduction in the patient’s severity of injury.

A word of caution

For the responder who arrives at the scene of an accident involving a late model vehicle the likelihood of undeployed airbags is greatly increased in vehicles with side impact bags. In a front or rear impact situation, the side bags are not designed to deploy. In a side impact, only the bag on the collision side should deploy, although deployment depends on the angle and severity of the impact. With some systems, if the passenger side seat is not occupied the bag will not deploy if the vehicle is hit on that side. As with live front airbags, if you must use forcible entry to rescue a patient it is extremely important to lessen the possibility of an accidental deployment. The most important first step to begin deactivation of the system is disconnection of the battery. In some vehicles this will be a challenge since batteries may not always be in the obvious under hood location. Some alternate locations are in wheel well areas, under rear seats, or in trunks. Other challenges to battery disconnection are with inverted vehicles’, or situations where a car has tunneled under another car, truck, or obstacle. In situations where you cannot access the battery, it is imperative that you stay clear of the potential deployment path of the live airbag as you perform the extrication. Additionally, once the battery has been disconnected, the airbag system contains capacitors to store energy. In the event of battery damage, the capacitor contains enough energy to trigger airbag inflation. This energy is stored for as little as one second to as much as 30 minutes, depending on vehicle make and model.

It might be prudent for your department to review SOP’s on door removal techniques. In the case of live side impact bags, removal from the hinge side first is a method for creating space between the patient and the live bag, as well as keeping away from the impact sensors. The sensors are typically located in the lower rear area of the door or in the lower “B” pillar. When the door is forced down and away from the patient, the likelihood of an injury from deployment is greatly reduced. Once both hinges are broken or severed the wires which run from the “A” pillar into the door will need to be cut in order to completely remove the door. Again, remember to stay clear of the potential deployment path, as cutting these wires may also trigger the airbag. Another alternate access method is full or partial roof removal. In all situations, attempt to position your patient away from deployment paths.

There are two new styles of side impact protection. The first, known as the Head Protection System or HPS, was introduced in the BMW 7 series in 1997. This bag is tubular in design, and deploys from the headliner and “A” pillar. It is anchored at the base of the “A” pillar and the roof rail behind the occupant’s head. As the bag inflates, the slack is eliminated since the material used shortens in length as it expands in diameter. This system offers substantial benefit to the victim of a side impact, greatly reducing the whiplash effect and protecting from intruding objects. In a 25-MPH pole intrusion test without HPS, the “G” forces to the head exceed 300. This system reduces that figure to less than 85 “G’s”. Additionally, the system, called the “Inflatable Tubular Structure” or ITS by Simula Automotive, the manufacturer, has proven to be effective in mitigating occupant ejection in rollover crashes since it remains inflated well after initial impact. Inflation occurs in fewer than 15 milliseconds (15/1,000 of a second) from sensor activation. The inflator is located under the dash area, and utilizes nitrocellulose as opposed to the more common sodium azide used for inflation of front airbags. BMW has completed introduction of this system in the 3, 5, and 7 series for 1998. Look for other car manufacturers to introduce this system in the near future. See box for handling procedures

Mercedes and Volvo will introduce the next system new to the side impact protection technology. Known as the window curtain, it is deployed along with the side bags, and protects the occupant from hard impact, glass splinters, and intruding objects. It measures roughly 6’ in length by 14” high and 2” thick, and deploys in 25 milliseconds from the roof rail area. The curtain is to be inflated by a compressed gas cylinder (95% Argon, 5% Helium) located in the “C” pillar. Caution should be exercised when performing a roof removal on vehicles utilizing this system. Prior to introduction of this system, initially in the ’99 “E” class models this fall, Mercedes will be providing location information on the gas cylinder. Volvo has announced their installation of the window curtain in the S80, due out October ’98.

An unusual style of protection, referred to as the knee airbag, has been introduced in the Kia Sportage. The knee airbag deploys from the lower dashboard area under the steering column, and is designed to reduce forces the knee area in frontal impacts.

Another technology has gained popularity in recent years. In 1981, Mercedes Benz introduced a device referred to as the Emergency Tensioning Retractor, or ETR. These are commonly called seatbelt pre-tensioners today, and have become as prevalent as the side impact airbag. This system is designed to take up the slack in the seatbelt using a pyrotechnic firing device to drive a piston through a cylinder. There is a cable attached to the piston, which either pulls directly on the belt at the latch side, or more commonly pulls on the retractor spool. Latch pull designs are located on the transmission tunnel side of the seat, while the spool pull design is located in the lower “B” pillar, with one exception. Volvo 850, S70, and the ’99 S80 positions the pretensioner mid “B” pillar, with the pyrotechnic chamber at the windowsill level. Roof removal on these models can be accomplished by making an inverted “V” cut into the roof over the “B” pillar.

Again, a case could be made for avoiding the “B” pillar during a forcible removal of the doors. If you suspect the vehicle you are working on has a live pretensioner system, it would help to cut or release the seatbelt as soon as it’s practical. Although most of these systems are electrically activated, many use a mechanically activated design that is not affected by battery disconnection.

The time has arrived for departments involved in vehicle extrication to begin efforts to keep abreast of the constantly changing automobile safety technology. The great news for those in the rescue profession is that the improvements and innovations from car manufacturers provide us with a more viable patient after the crash. Additionally, new Federal Motor Vehicle Standards for rollover and side impact protection are reducing the entrapments from collapsing roofs and crushed doors. However, we must understand that live pyrotechnic systems need to be approached with caution and understanding, and that the materials used to pass federal standards for crush resistance may thwart the efforts to cut or spread areas that were not nearly as tough in the past. A great way to develop pre plans for various vehicles is to visit local car dealers and request permission to do some snooping. Most information on safety devices will be found on the window sticker. Looking under the hood will let you know immediately if you will have a challenge disconnecting the battery. Ask about glass during your inquiry, as laminated or other break resistant types of glass are becoming popular.

Remember that no list stays current for very long. Mid year changes are common, and staying up to date can be a challenge

Dealing with side impact airbags
- Disconnect battery if possible
- Ease patient away from deployment path if moving will not cause further injury
- Use alternative door removal techniques i.e. hinge first or
- Roof removal/flap
- Remember the live front airbags! Beware---

BMW Head Protection System
- Disconnect battery, located under rear seat or in trunk
- If deployed, simply cut out
- If undeployed, do not lean into vehicle through the front window areas!
- Roof removal no problem, but remember to stay clear of “A” pillar area after removal

Safety Suggestion:
Utilize battery before disconnecting
1. Move electric seats rearward if patient condition permits
2. Open electric locks
3. Open electric windows