Inner Sanctum

Sport utility vehicles are under siege again. After being slammed by political and environmental groups for their poor gas economy, SUVs are now the focus of federal legislators looking at trends in truck-related accident fatalities. As automakers begin to respond, the net result in the short run may be a spate of new, more sophisticated safety systems for vehicle interiors.

SUV rollovers have been one of the top concerns behind recent activity in Washington, D.C. Since 1991, the number of rollover-related fatalities has more than doubled. The main cause of the fatalities is the fact that occupants are ejected, or partially ejected from the cabin.

So far, systems like curtain airbags have been introduced to keep passengers inside the vehicle and reduce head trauma during a rollover. But down the line, automakers and suppliers are looking to take a more holistic approach to better manage the occupant inside the cabin as the vehicle rolls.

“With the proliferation of airbags, we are working to design them into the interior as a complimentary system overall, working in tandem with seat belt features, such as pretensioning and load management, to provide a complete solution,” says Thomas Vos, director of safety systems at TRW Automotive.

Side-curtain air bag systems are designed to not only protect occupants from injury in roll over accidents, but will also keep limbs inside the the vehicle.

Dupont’s SentryGlas, laminated side windows on the BMW 7-Series will stay in place when broken and serve as a window net to keep occupants limbs inside.

“The belt still plays an important role in keeping the head away from the window, so you have to look at the overall performance.”

The automakers introducing curtain airbags as options on their top-selling SUVs include DaimlerChrysler on the Jeep Grand Cherokee and Liberty, Ford with its Explorer and Mercury Mountaineer and General Motors on the Saturn VUE.

The question on the table is whether or not the government will make them mandatory. Legislators have been reviewing rollovers for some time, with no active regulation implemented or pending. But NHTSA chief Dr. Jeffrey Runge has placed SUV rollover-related deaths directly in the line of fire, insisting that some solution must be found to reduce the increasing fatality rate.

Not surprisingly, automakers don’t feel the need for direct government intervention. “We tend to be driven by real world data, and at this point we do not see any need for government regulation in the area of rollovers and SUVs,” says Michael Berube, manager of safety planning at DaimlerChrysler. “This is an issue that the government has looked at a number of times and in the end they said don’t see a rule or regulation that is appropriate.”

While curtain airbags will offer some protection during rollovers, limbs or even a head can still work around the airbag creating the potential for major trauma. DuPont Automotive says that during a rollover, its SentryGLAS product introduced originally as a security glass on the BMW 7-Series, would stay intact even after it shatters, acting as a safety net to keep occupants and all of their appendages inside the vehicle.

“Laminated glass has the durability to meet automakers’ requirements while addressing safety issues such as occupant full or partial ejection. It also provides a better reaction surface for side or roof airbags and reduces flying glass lacerations and lowers the potential for airbag puncture,” says Michael Sanders, Dupont automotive marketing and development manager.

One of the bigger problems facing automakers is the cost associated with airbag replacement. Current systems are focused on making absolutely certain a crash event is taking place before the bag is deployed. Popping off the airbags during a close scrape or a near miss would not only be expensive, it could even instigate the accident.

So automakers are looking at other ‘reusable’ system concepts that might allow for deployment in a scenario where a crash is imminent but has not yet occurred. Pop-out side panels on door interiors that extend with an accordion-style airbag could offer sideimpact protection for the thorax area. The panel, after it was deployed, could be simply pushed back into position by the passenger if the crash was not severe. This particular configuration would allow automakers to deploy the panel before the crash, whether or not it actually takes place, buying precious milliseconds to protect the passenger and keeping the replacement costs and driver intrusion to a minimum.

The convergence of different safety systems working together in a rollover event conceptually is a target that automakers are beginning to embrace. In a rollover crash, or any other type of accident, seats, airbags, belts, and even steering wheels and interior panels would react to optimize the cabin environment for safety, minimizing injury to the occupants. The system would analyze data about occupant position, size and information from sensors and make adjustments as needed.

Mercedes-Benz has introduced such a system, dubbed Pre-Safe, on its 2003 SClass model. Using existing sensor data on the S-Class, the system will trigger a variety of interior adjustments when it senses emergency braking, severe over-steer and understeer, or an imminent rollover. Under these conditions, the Pre-Safe system will tighten the seatbelts and return all passenger seats to safer positions. The driver’s seat is not modified since they are more likely to be in a safe position compared with other passengers in the car. During a possible rollover event, Pre- Safe even closes the sunroof. Mercedes says that future versions may use pop-out panels to move occupants further away from deformation zones or even raise the vehicle height to improve crash compatibility.

The subject of vehicle-to-vehicle compatibility is another hot topic at NHTSA, which is not solely concerned with rollovers. In fact, the leading cause of accident fatalities is alcohol (in 2001, NHTSA reported that 17,488 fatalities, or about 41 percent of the total, were alcohol related). But Dr Runge’s office has cited the issue of incompatibility — the mismatch between a large, heavy SUV with a high bumper system and a lighter, lower passenger car — as another growing contributor to traffic fatalities.

Data shows a disproportionate number of deaths among passenger car occupants when the car is struck by a pickup or SUV. For every 100,000 crashes between passenger cars and pickups there are 293 deaths, and between cars and SUVs, 205 deaths. By comparison, when a car collides with another car, there are only 77 deaths per 100,000 crashes.

“If a heavy vehicle runs into a light vehicle, there always will be incompatibility. The people in the heavier vehicle will always come out better than those in the lighter vehicle,” says Priya Prasad, Ford’s senior safety engineer. Prasad says that the change in the accident statistics is due in part to the changing mix in the U.S. vehicle fleet. As more SUVs and pickups hit the road, they are more likely be involved in fatal accidents.

TRW Automotive’s occupant vision system features a stereo camera configuration capable of both occupant classification and determining out-of-position occupants. The camera is small enough to be mounted in the overhead console.

Again, in the short run, automakers are likely to turn to airbags to solve the problem. The same systems that hold occupants in their sport-utilities during a rollover also can provide head and neck protection when a sport-utility vehicle smacks into a passenger car. With so many curtain airbag systems already available as optional equipment on existing models, automakers may feel a built in solution is already available.

But certain types of deadly crashes, side impacts for example, require exceptional speed to deploy an airbag ahead of the deformation. Unlike a frontal crash, there is little space between the offending vehicle, the sensor and the occupant.

Mercedes-Benz Pre-Safe system can detect an imminent collison and engage occupant protection systems before the impact occurs.

“Faster deployment time for side-impact airbags is critical in addressing these higher bumper systems hitting passenger cars,” says Bruce Wrenbeck, North American director of safety electronics and restraint systems at SiemensVDO Automotive. “Today we’re looking at how to get the airbags out in time to protect the occupant.”  Newer pressure-based sensors that measure the volumetric change of the air in door cavities and other soft structures may wind up replacing acceleration-based sensors moving forward. “For a side event, an acceleration- based sensor will take about 9-10 milliseconds and a pressure-based sensor will do it in less than five,” says Wrenbeck. SiemensVDO already supplies the pressurebased sensor technology to European automakers, including Saab and Opel, and says other companies are coming on stream. Most of these recent safety systems already are being introduced into production vehicles. As engineers look further out, some see more integration, bringing information from the outside of the vehicle into the vehicle interior and its host of safety systems.

“We will start to get into pre-crash sensing, a whole surround-sensing concept, using infra-red, video and even lasers to watch what is outside of the car and fuse that information with the controls for the active safety systems to make smarter choices on the deployment of airbags and other devices,” says Bob Rivard, vice president of advanced technology at Robert Bosch Corp.

These revolutionary systems also offer the added potential to migrate into crash avoidance systems. Radar proximity systems already have been introduced for very small distances. The problem, Rivard says, is distinguishing one object from another at larger distances. Hybrid camera and radar systems may offer possible solutions to help distinguish objects and let interior safety systems make better decisions.

Whether or not these applications are ready for real-world production application is yet another problem. Most of the technologies for advanced airbags and even advanced sensors are available today. But there may be a wait before car buyers begin to see long-range radar systems and camera systems inside their vehicles. “To teach a system to make literally pixel-level judgments and to teach it to distinguish patterns like the difference between a person and a telephone pole is very challenging. We know some of the core sensor technologies are feasible, but now we need to integrate it into a robust product,” says Rivard.

Individually, each new technology offers potential safety enhancements in particular types of accidents. Rollover sensors, curtain airbags and safer interiors can help reduce the severity of injuries in a crash, but not necessarily address the root cause.

“When you look at the data and find the contributing factors, mass dominates. We are already under pressure to reduce mass because of fuel economy,” says Berube. “A lot of people are searching for simple answers and I applaud NHTSA for resisting the grab for simple answer. Vehicle incompatibility has been talked about for decades.”

Future crash avoidance systems will use radar to detect on-coming obstacles and alert safety systems before the impact occurs and in some instances help avoid it all completely.

For the moment, NHTSA seems content to the auto industry address the problem on own. In a rare act of self-reproach following meetings in Washington, D.C., automakers recently acknowledged that sport utility vehicles and pickup trucks pose a greater risk to passenger car occupants, and agreed to pull together to tackle the issue. “These systems are only going to increase availability. SUVs are extremely safe vehicles already, so there really isn’t a compelling need in our mind for government regulation,” says Berube.

But the threat of potential regulation still is very real. Recently, the government passed FMVSS208, legislation that among other things requires systems to recognize the presence of an occupant and their weight classification starting in model year 2004. This type of mandate could effectively require advanced sensor technologies inside vehicles to improve on airbag performance.

When the final analysis is complete, NHTSA may find it has served less as a regulatory body, and more as a marketing conduit for the automakers. Other safety-related technologies like anti-lock brakes fell short when consumers were asked to pay for it as an option. But the publicity surrounding SUV rollovers and incompatibility with passenger cars make a compelling case for car buyers in the market today.

“We are hoping that NHTSA can create a pull in the market. Take their new car assessment program,” says Ford’s Prasad. “Maybe NHTSA can look at some of the systems we are offering and give us credit for them. This might wind up creating more demand.”