April 2005
| Making sense of safety information What are the key safety issues and where to find the facts. Crash protection | Accident avoidance | Rollover resistance Head restraints | Electronic stability control (ESC) | Blind spots Load capacity | Child safety Safety is a key part of any vehicle buying decision, but it’s not easy to assess a vehicle’s overall safety potential. Some buyers think they need a large vehicle such as an SUV or pickup because of its perceived crash safety. Others are concerned with the fact that there is a higher incidence of rollover accidents involving these types of vehicles. In fact, there are many factors to consider when evaluating overall safety. Here, we highlight the various safety issues you should consider and where to find additional information. Crash protection (back to top) How well a vehicle protects its occupants from injury depends primarily on its structural design and safety systems. Safety belts are the single most important element, with air-bag systems providing additional protection. In addition, all vehicles have “crumple zones” in the front that are designed to collapse in a way that helps absorb the crash energy and minimize any deformation of the cabin. The better the vehicle manages this energy, the less chance that occupants will suffer serious injury. The only independent crash-test results are those from the National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety (IIHS). NHTSA conducts two types of crash tests: full frontal and side impact. NHTSA tests are a good indication of how well a vehicle’s safety belts and air bags protect the occupants in specific types of impacts. Each is scored on a five-star scale, with fewer stars indicating a greater likelihood of injury or death. Separate ratings are given in the frontal test for the driver and front passenger, and in the side impact for the driver and left rear passenger. The IIHS tests vehicles in an offset-frontal crash, the more common type of head-on crash. In an offset-crash test, only the portion of the vehicle in front of the driver impacts a barrier. This test challenges the car’s structural integrity and its ability to protect the area around the driver without collapsing. Vehicles are rated as Good, Acceptable, Marginal, or Poor. Recently, the IIHS began conducting side-impact tests, although not many vehicles have yet been tested. We will include those results in our vehicle profiles when more are available. For crash-test results on specific models, refer to the vehicle profiles or to the appropriate NHTSA and IIHS Web sites. The effect of size and weight. The frontal crash tests performed by NHTSA and IIHS simulate a collision between two vehicles of the same weight. However, many real-world collisions occur between vehicles that are of different sizes and weights. As the IIHS states, “All else being equal, larger and heavier vehicles are safer than smaller, lighter ones” in a crash. This is because larger, heavier vehicles project more of their energy into other vehicles, at the smaller vehicles' expense. This, in turn, helps to better protect the larger vehicles' occupants. Higher bumper heights. In a crash, the higher bumper on many taller vehicles, such as SUVs and trucks, hits a typical passenger car above the car's bumper line and sill, exerting its force into weaker portions of the smaller vehicle and inflicting greater damage. To address this, many SUVs--especially car-based ones--are being designed with lower bumpers. Late last year, a most automakers agreed to implement new specifications on all their light trucks (SUVs, pickups, and minivans) to help alleviate this problem, but those designs won’t begin to be phased in on all vehicles until the 2008 model year. Accident avoidance (back to top) A vehicle's ability to help you avoid an accident is just as important as its ability to protect you in a crash. That’s why CR evaluates these factors on every vehicle it tests. The two most important factors are braking and emergency handling. Braking. A vehicle's braking system has to stop the vehicle in as short a distance as possible and keep the vehicle under control and on its intended path. Our tests measure braking performance on both dry and wet pavement, and evaluate the effectiveness of a vehicle’s antilock braking system (ABS). Emergency handling. The more controllable and secure a vehicle is when pressed to its handling limits, the better able you'll be to avoid an accident by, say, steering around an obstacle without losing control. We rate emergency handling on the basis of three tests. We use a double-lane-change avoidance maneuver to evaluate a vehicle’s handling in a situation in which a driver needs to suddenly steer around an obstacle on the road. In the other tests, vehicles are pushed to their cornering limits around our handling course and skidpad. Other accident-avoidance factors. Acceleration, driving position, visibility, and even seat comfort also can affect accident avoidance. Quick acceleration can make it easier to merge safely into highway traffic or avoid an accident. Seating position can affect outward visibility and comfort. Seat comfort also plays a role because a driver who is fatigued or uncomfortable may concentrate less on the road. Rollover resistance (back to top) The SUV safety issue that has garnered the most attention is rollover. According to NHTSA, SUVs have a rollover rate that is two to three times that of passenger cars. According to government figures for 2002, about 50 percent of all deaths in SUVs occured in single-vehicle rollovers. By contrasts, only 20 percent of passenger-car fatalities were because of a rollover. It's mostly a matter of physics. A taller vehicle has a higher center of gravity, which makes it more top-heavy than one that sits lower. In a situation where a vehicle is subjected to strong sideways forces, such as in a sudden cornering maneuver, it's easier for a taller vehicle to roll over. During normal circumstances, drivers rarely encounter such strong forces but an emergency can happen at any time without warning. A rollover becomes a danger in several types of situations: An accident-avoidance maneuver. If a driver swerves sharply to avoid an obstacle or person in the road, the hard cornering forces can cause the vehicle to tip onto two wheels or roll over. Alternately, the vehicle can strike a curb, guardrail, or other low obstacle and “trip” over it, causing the vehicle to roll. Taking a corner too fast for the conditions. This can cause a vehicle to slide or skid to the outside of the turn where it could go off the pavement or, as above, trip over a low obstacle. A tire blowout. At least some of the accidents that initiated the massive Firestone tire recall in 2000 took place when a sudden tire blowout caused the driver to lose control, causing the vehicle to swerve sharply and roll over. To give consumers a way of telling which vehicles have a higher rollover propensity than others, NHTSA has developed a five-star rating, called the Rollover Resistance Rating (RRR). Until recently, the RRR was based solely on a vehicle's “static stability factor (SSF),” which is determined from measurements of its track width and center of gravity. Because the SSF is based on measurements of a stationary vehicle rather than on a dynamic road test, the rating doesn't account for vehicles' different suspension designs, tires, or the presence of an electronic stability-control system--any of which can make a significant difference. Now, however, NHTSA is also performing a dynamic rollover test with moving vehicles. The results of this test are now being combined with a vehicle’s SSF to arrive at the final rollover rating. NHTSA Rollover Resistance Ratings can be accessed online at www.nhtsa.dot.gov/ncap. Head restraints (back to top) There are no independent crash tests for rear impacts. Although “rear enders” have a low fatality rate, they have a high injury rate, especially for whiplash neck injuries. A car’s head restraints are vital for guarding against whiplash. Restraints need to be tall enough to cushion the head above the top of the spine. The top of the headrest should be at least as high as the top of the person’s ear. Many cars’ head restraints adjust for height, although many people don’t take the time to do it. Look for headrests that lock in the raised position. Those that do not can be forced down in a crash, losing effectiveness. Many cars’ rear restraints are too low to do much good, which we note in CR’s monthly road-test reports. The IIHS Web site also provides good information on head restraints, as well as the institute’s ratings of the restraints in different cars. Electronic stability control (ESC) (back to top) Electronic stability control is highly recommended by CR’s auto experts, particularly on SUVs. Stability control is designed to help keep the vehicle under control and on its intended path during cornering, preventing sliding or skidding. It’s especially helpful in slippery conditions or when a vehicle exceeds its handling limits due to an emergency situation. In our testing, CR has found that ESC can significantly improve a vehicle's emergency-handling capabilities and help keep a vehicle from getting into a situation where it can roll over. However, electronic stability control is not a cure-all for out-of-control driving or inherent handling problems. It’s effectiveness depends on how it is programmed and how it is integrated with the vehicle. Electronic stability control started on luxury cars and has been catching on for the past few years. To confuse matters, automakers each have a proprietary name for their stability control systems (see the accompanying table). To help consumers identify the system in a vehicle's features list, the Society of Automotive Engineers has asked that all manufacturers use electronic stability control or ESC, as common terminology when referring to their stability-control systems. Consumer Reports supports this announcement, and feels it will help consumers know what they are buying. If in doubt whether a car has it, find out before you buy. In its XC90, Volvo introduced a system called Roll Stability Control that expands the capability of the conventional system. This uses gyroscopic sensors to monitor when the vehicle leans beyond a predetermined angle at a given speed, indicating that a rollover is imminent. If so, the system immediately reacts to help correct the situation by reducing engine power and selectively applying individual brakes. Nissan offers a similar optional system in its Pathfinder Armada SUV. Blind spots (back to top) Every year, children are injured and killed because drivers don’t see them while backing up. According to Kids and Cars, a nonprofit group that wants to improve child safety around cars, backover incidents in 2003 killed at least 91 children. A contributing factor is that larger vehicles, such as SUVs, pickups, and minivans, have larger blind spots--the area behind a vehicle that the driver can’t see. Some SUVs and minivans are now available with a rear-view video camera that gives the driver a wide-angle view of much of the area that’s usually hidden in the blind spot. CR’s testing has shown that when used regularly these can be an effective aid in reducing backover accidents. To check a vehicle’s blind spot, sit in the driver’s seat while a friend holds a hand at about waist level. Have the person walk back until you can see the hand through the rear window. This will give you an idea of how big the blind spot is. (See our report on The problem of blind spots.) Load capacity (back to top) It's natural to assume that if a vehicle has a large cargo area, you should be able to fill it without worrying about overloading the vehicle. But that’s not always the case. Some vehicles have a large cargo area but a relatively low load-carrying capacity--the maximum combined weight of people and cargo that the vehicle is designed to handle safely. Overloading a vehicle can compromise its safety by degrading its handling, stressing its brakes, and possibly overheating its tires, which increases the risk of tire failure. Unfortunately, most auto manufacturers don’t provide load-capacity specifications in a way that’s easily accessible to the consumer. Exceptions include Honda, Jeep, Mercedes-Benz, Nissan, and Toyota. However, all vehicles produced after Sept. 1, 2004 will be required to have a load label. Consumer Reports already publishes the load capacity on every vehicle it tests. Child safety (back to top) Child-safety seats save lives and should be used until a child is big enough to use the vehicle’s regular safety belt. However, securing a child seat can sometimes be difficult. All new vehicles now have a universal system called LATCH (Lower Anchors and Tethers for Children) that is designed to make attachment easier and more secure. But we have found the attachments in many cars hard to access. CR’s test staff checks child-seat compatibility on every vehicle they test, with results noted in the road-test reports that appear each month in Consumer Reports and on ConsumerReports.org. When looking at vehicles, bring along your child’s seat and try it out before buying. Window switches. Another child-safety consideration is power-window switches. Children have accidentally activated some power windows while leaning out and have been killed or injured by the closing window. The easiest types to inadvertently activate are horizontal rocker and toggle switches on the door’s armrest, which can raise the window when pushed down. Lever-type switches, which are flush with the surrounding trim and only raise the window when pulled up, are a safer design. |
