Keeping people safe in cars has been a priority for decades now, but until recently most of the focus has been on protecting the driver and front passenger. Since those are the seats most frequently occupied in a vehicle, that approach makes sense.
But what about rear-seat occupants? They usually don't have the advantage of the advanced safety features that front-seat occupants have, but that doesn't necessarily mean they're less safe.
So we did some digging. And it turns out that, yes, they could indeed be less safe. But there are more factors in play than the amount of safety features your car has. In the event of a collision, the safety of your rear-seaters depends on their age and size, the type of vehicle you drive, and the type and severity of the crash.
When rear passengers are at risk
The basic laws of physics mean that any vehicle occupant has the greatest risk of injury when the initial point of impact is closest to them. Since frontal collisions are the most common type of crash, representing about 50 percent of all passenger vehicle occupant deaths in 2007 according to the Insurance Institute for Highway Safety (IIHS), rear-seat passengers in general have less of a risk of injury during a frontal collision simply because they are more likely to be further away from the initial point of impact.
However, this does not hold true for all age groups. A 2005 NHTSA study assessed the risk of serious injury and death to occupants seated in the front seat versus the rear seat, in a frontal impact. This study showed that restrained occupants younger than age 50 had less risk when seated in the rear, while restrained occupants older than 50 were better off in the front seat because the airbag afforded them greater protection.
Side-impact collisions and rollover accidents are another concern to rear-seat passengers. In 2007, 28 percent of car and truck occupants died in a side impact collision. The statistics on rollover collisions are more disturbing, as they have a higher rate of death: In 2007, 35 percent of rollovers resulted in a fatality. These rates are beginning to decrease as more automakers include side airbags that not only extend to the third row but also offer added rollover protection.
Although rear-end collisions are one of the most common types of crash, most rear-end collisions occur at lower speeds, resulting in deaths only four percent of the time. Instead, neck injuries, including whiplash, are the most common serious injury reported in rear-end collisions.
Since rear-seat passengers are less likely to have safety features like airbags, three-point seatbelts with pre-tensioners and adjustable head restraints to protect them, they are at greater risk in these types of collisions. And if they happen to be riding in a small car or SUV, the risk is even higher.
Small cars vs. sport-utes
While they represent opposite ends of the spectrum in size, small cars and sport-utility vehicles pose the highest risk of death in a collision. In a study of 2004 accident data, the NHTSA found that the highest incidence of fatality was in compact cars, followed by compact pickups, then midsize SUVs.
With the increasing number of entries in the small-car segment, more of these vehicles are likely to carry rear-seat passengers. Because these small cars are generally in the entry-level segment, many of them lack the safety features that are standard on larger, more expensive vehicles. However, manufacturers are beginning to respond. The current-generation Hyundai Accent and Kia Rio have front-seat side airbags and full-length side curtain airbags as standard fare, while the Honda Fit comes with a full menu of airbags, plus standard antilock brakes.
Automakers are also going to greater lengths to ensure their small cars perform well in crash tests, though a crash test rating is only comparable to a group of cars of similar size and weight. In other words, the federal government's four-star rating of the compact Scion xD does not make it as safe as the midsize Volkswagen Jetta, which also received four stars.
When it comes to SUVs, it's important to keep in mind that rear-seat passengers are not necessarily safer just because they are in a larger, heavier vehicle. A recent study by the Partners for Child Passenger Safety published in the medical journal Pediatrics found that children ranging from infants to age 15 were no safer in SUVs than they were riding in cars, due to the increased risk of rollovers in SUVs.
In addition, a child seated in the third row is not necessarily safer in a frontal collision than a child in the second row. A 2005 study by Transport Canada (the Canadian equivalent of the NHTSA) showed that youngsters are likely to face the same forces in a frontal collision regardless of whether they are seated in the second or third row of the vehicle. The study, which involved a crash test dummy representing a 6-year-old seated in a booster seat in the second and third rows, found equally elevated forces in both rows.
Plus, third-row occupants are at greater risk than second-row occupants in rear-end and side-impact collisions, because they're closer to the rear of the vehicle in a rear impact and are even less likely to have side airbags to protect them. Currently, only about 55 percent of vehicles with third-row seating have side airbags that cover all three rows. And bear in mind that even if your vehicle does have three-row side curtain airbags, they may not extend down far enough to protect children. (For more on this topic, see our article, "Who Benefits From Side and Head Airbags?")
Third-row occupants are also vulnerable to flaws in the seatback's design when they're involved in rear-end collisions. Many seatbacks are either too rigid, which can cause whiplash, or too yielding, which can cause the seat to partially or fully collapse, allowing the occupant's head to contact the rear window, liftgate or even an intruding vehicle in a severe crash. This is particularly a concern in small and midsize SUVs, where the third-row seatback is usually much closer to the rear window than in full-size SUVs. In an informal survey of vehicles with three rows, distances between the third row and the rear window ranged from 8 to 33 inches, with the smaller SUVs generally having the shortest distances.
Is 8 inches or even 1 foot enough space? It depends not only on the strength of the seatback, but on the other safety features built into the vehicle. When Toyota, for example, added an optional third row to the Highlander midsize SUV, it included extra bracing around the rear door opening, along both sides of the cargo bay and up over the rear wheels to help channel the energy away from occupants during a crash.
Volvo considers 12 inches the minimum safe distance between the head of a third-row occupant and the back of the vehicle, according to company spokesperson Dan Johnston. Even with that amount of space, the company has reinforced the rear and tailgate of its XC90 midsize SUV with boron and ultrahigh-strength steel to reduce the possibility of intrusion into the passenger space.
Seatbelt fit is important, too
A seatbelt that fits properly is key to protecting any occupant in any type of crash, but rear seatbelts are less likely to fit occupants well because of the design of the rear seats and the mounting of the belt itself. Adult occupants with a short torso are more likely to find the shoulder portion of the belt riding too high and cutting across their necks, while adult occupants of all sizes may find that the lap belt rides too high because of the design of the seat itself.
One study published by the Society of Automotive Engineers (SAE) indicated that the standard three-point design would be more effective if the design were reversed for rear-seat occupants — meaning a belt that goes over the right shoulder and buckles by the left hip for driver-side rear occupants, the opposite of what is typically found in vehicles today. Researchers found this design improved the seatbelt geometry for a wider range of occupants, increasing its protective benefits as well as making it more comfortable for occupants.
This so-called "reversed shoulder belt geometry" was used on some BMWs from the late 1980s to the late 1990s. The practice was discontinued when BMW began phasing in three-point belts for the rear center passenger.
"It's really a matter of real estate," BMW spokesperson William Scully told us. "There really isn't enough room on the parcel shelf to mount all three of the rear belt retractors inboard and achieve proper belt geometry. Three inboard shoulder belts could get confusing for rear passengers and would get in the way in models with folding rear seats."
Currently, the reversed belt design is only found on the BMW 3 Series convertible. This vehicle holds just two rear passengers, and mounting the shoulder belt the traditional way interferes with the convertible's roof mechanisms.
Future efforts to protect rear passengers
Future vehicles are likely to offer more protection to rear-seat passengers in the event of a collision. Vehicles with head curtain airbags for rear occupants are becoming more common and researchers are looking at other ways to improve rear-passenger safety.
One possibility is Ford's inflatable safety belt. Engineers have developed a small, tubelike airbag that deploys from the seatbelt in the chest area. "We feel it will be useful to prevent rib fractures and neck loads, especially in older passengers," says Priya Prisad, safety technical fellow at Ford. This sausage-shaped airbag deploys in both frontal and side impacts and can stay inflated for longer periods to protect during rollovers. Though still undergoing testing, the inflatable safety belt is likely to be used in future vehicles, according to Prisad.
Until then, it's wise to shop carefully if you regularly carry passengers in the backseat of your vehicle. If rear-seat side airbags are optional, pay extra to get them. If you're a parent, make sure that if you're looking at an SUV, it has been reinforced to provide maximum protection to third-row occupants in rear impacts. Finally, look at crash test scores, particularly the side-impact and rear-end ratings from the IIHS.