Buzz
Side curtain airbags are becoming more widely used, but how exactly do they enhance safety on the road?
©iStockphoto.com/Sieto VerverIn the quest to design safer cars, it might seem like manufacturers are trying to fit airbags in every possible space. One notable recent development, the side curtain airbag, has proven to be both effective and adaptable.
For years, side curtain airbags have earned high safety ratings for passenger cars and minivans. Recently, however, automakers have been finding innovative ways to tailor side curtain technology for more specific use cases, especially in high-risk vehicles. For instance, drivers of convertibles and SUVs now benefit from side curtain airbags offering added protection during rollovers. These airbags could also become essential as sub-compacts gain popularity. Although the structural safety of tiny cars has been questioned by both consumers and regulators, a new microcar will feature curtain airbags designed to safeguard passengers' necks. If these airbags prove effective during rear collisions, they could play a key role in shifting public perception about small, efficient cars.
These advancements represent a significant leap from basic airbags, which were initially placed in the steering wheel and dashboard to absorb crash impacts. Dual front airbags became a mandatory feature in the United States starting with the 1998 model year (see How Airbags Work for a detailed explanation).
Side curtain airbags are intended to work alongside traditional airbag systems, enhancing vehicle safety overall. Although currently optional in the United States, the National Highway Traffic Safety Administration (NHTSA) required all new vehicles to include them to meet tougher side impact safety standards by 2013 [source: Benton].
In this article, we will explore how side curtain airbags provide protection and examine their ongoing evolution. Next, we'll delve into how and why these airbags have developed over time.
Evolution of Side Curtain Airbags
Although traditional airbags marked a major breakthrough, they were most effective in head-on crashes. For instance, in a frontal collision, the engine compartment is designed to crumple, absorbing much of the impact. However, when a car is struck from the side, the only protection is the door and a few inches of space, leaving occupants vulnerable. Drivers and front passengers were at significant risk from side collisions, with rear passengers often overlooked.
Instead of starting from scratch, automakers analyzed crash test data to determine the most effective areas for additional airbags. Side impacts are especially dangerous due to the limited crumple zone, so airbags were added to doors and front seats to protect the chest and thorax of front-seat passengers.
One early innovation was the head airbag, also known as the Inflatable Tubular Structure, which became widespread in vehicles after 1998. When a side impact is detected, the tube inflates and forms a solid 5-inch (12-centimeter) barrier across both the front and rear windows. This structure keeps passengers' heads from slamming into hard surfaces, although it does not protect against injuries caused by limbs or flying debris.
This led to the introduction of side curtain airbags, which deploy in a collision to provide protection during a side impact. These airbags are typically mounted in the headliner above the doors and windows. Like traditional airbags, when the sensor detects a side impact, some airbags deploy through the headliner, while others are stored in a compartment beneath a panel that bursts open.
Two convertibles pioneered a variation of this technology, highlighting the flexibility of side curtain airbags. Both Porsche and Volvo claim to be the first to install door-mounted side curtain airbags [sources: Mello, Wardlaw]. These airbags feature vertical air chambers, similar to an air mattress, that have a firm structure allowing them to deploy upward and cover the window area. Unlike roof-mounted airbags, these door-mounted versions offer protection during side collisions even when the convertible top is down.
Although the technology behind side curtain airbags is similar to other airbag types, they provide additional protection that traditional airbags do not, which will be further explored in the next section.
Each car is equipped with sensors, typically located in the B pillars (the structural area between the front and rear doors) or sometimes in the door itself. Upon detecting an impact, the sensor calculates the necessary airbag deployment and activates a gas inflator. The gas inflates the airbag, pushing it out of its housing while remaining securely attached. The bag inflates quickly, and the gas disperses to deflate the airbag. This entire process occurs in under a second.
Advantages of Side Curtain Airbags
We've already discussed how side curtain airbags were initially developed to protect passengers' heads and necks in side collisions by covering all windows and pillar trim. But their role extends beyond that. Here are some additional ways side curtain airbags keep you and your passengers safe:
Because side curtains often cover nearly all of the window area, they act as a barrier that can help prevent passengers from being ejected during a crash [source: Safercar]. Even when seatbelts are securely fastened, a collision may still force limbs through the windows, risking serious injury. The side curtains' internal structure is strong enough to significantly reduce the chances of full or partial ejection. They also help block intrusions like metal, broken glass, and other debris from the crash, lowering the risk of injuries like broken bones, cuts, and bruises.
Some curtain airbags are specially designed for rollover crashes, a feature first introduced on the Ford Explorer [source: Mello]. These airbags include sensors that detect an imminent rollover by monitoring the vehicle's tilt. When deployed, they stay inflated longer than regular airbags to account for the extended danger occupants face during a rollover. While regular airbags deflate almost immediately after deployment, rollover curtains stay inflated for several seconds, providing continued protection as people are tossed around inside the vehicle. These airbags use cold helium to maintain their volume over an extended period. This feature is most commonly found in SUVs, which are more prone to rollovers due to their higher center of gravity.
The safety reputation of traditional airbags was compromised when early models caused harm to children. Over time, the technology has been improved, and now parents are advised to keep young children away from front and side-impact airbags. However, side curtain airbags don't carry the same risks. The Insurance Industry for Highway Safety reports that while children might not fully benefit from the protection of curtain airbags, experts agree that these airbags are generally safe for children [source: Mello]. Unlike front and torso airbags, the side curtains' deployment doesn’t forcefully intrude into the occupants' space.
Side curtain airbags are intended to enhance traditional airbags, not replace them. Next, we’ll look into the different types of airbags and explore how all these systems work in tandem to protect you.
Side curtain airbags are constructed similarly to traditional airbags, with key components including fabric (usually coated with a lubricating powder), a gas inflator, and a sensor module.
The main differences between side curtain and traditional airbags are their size and design. Side curtains require more fabric due to their flat shape, resulting in a larger surface area. They’re engineered with several chambers to improve their resistance to impact. These chambers allow the vehicle's crash sensors to assess the impact and deploy gas only where necessary, causing the curtain to inflate and deflate faster [source: WIPO].
Side Curtain Airbags Alongside Other Airbags
As government safety standards evolve and new technologies prove their effectiveness, it’s important to understand how all the safety systems in your car work together. Side curtain airbags were introduced as a supplementary feature to offer protection where traditional airbags were lacking, but traditional airbags are still essential. These systems may be known by different names, depending on the original equipment manufacturer (OEM), regulatory bodies, or marketing terminology, but understanding their basic functions is crucial to fully comprehending their role in your vehicle’s safety.
Frontal airbags are installed in the steering wheel and dashboard, while side airbags are typically positioned in the seat frame or door, depending on the manufacturer and supplier. Not all airbags in a vehicle will deploy during a collision; the vehicle’s airbag system uses a network of sensors to determine which airbags need to be activated [source: WIPO]. Below are some common types of airbags you may find in your car:
The driver airbag is located in the steering wheel and is designed to protect the driver during most types of collisions, including frontal, rear, and side impacts [source: Autoliv: Driver]. If the driver is propelled forward during a crash, they will most likely come into contact with the driver airbag.
The passenger airbag functions similarly to the driver airbag, deploying under similar circumstances. It’s typically positioned in the dashboard of most vehicles [source: Autoliv: Passenger]. This airbag poses a significant risk to small children and can result in serious injury or even death.
The thorax airbag is designed to reduce severe chest injuries in side-impact collisions, with one manufacturer estimating a 25 percent reduction in injury severity [source: Autoliv: Thorax]. Upon deployment, it forms a protective barrier between the occupant and the door.
The head thorax airbag serves a similar function to the thorax airbag, offering protection from side-impact collisions [source: Autoliv: Head]. However, it is larger, providing additional coverage to safeguard the head as well.
The pelvis thorax airbag inflates near the occupant's hips to reduce the risk of lower body injuries during a side impact. This compact airbag deploys rapidly from the seat’s frame to provide quick protection [source: Autoliv: Pelvis].
Side curtain airbags are gaining popularity among both manufacturers and consumers. Continue reading to find out their cost and what that might mean for their widespread availability.
The Toyota iQ, a microcar launched in Europe and Japan in 2009, was the first vehicle to feature rear curtain airbags. These airbags are similar to side curtain airbags but are mounted above the hatch window and deploy downward from the roof lining when the car is rear-ended. Due to the minimal rear crumple zone in microcars like the iQ, Toyota claims these airbags will double the rear head protection for backseat passengers [source: Newcomb].
Availability and Cost of Side Curtain Airbags
Thanks to the highly competitive nature of the auto industry and ever-stricter federal safety regulations, consumers now have many options when it comes to purchasing vehicles with side curtain airbags.
Cars equipped with side curtain airbags feature a small emblem near the roof or pillar that identifies their presence, similar to the ones seen on steering wheels, dashboards, and seats. These emblems often display the acronyms SRS (Supplemental Restraint System) or SIR (Supplemental Inflatable Restraint). Following the NHTSA's 2007 decision to enhance side impact collision standards, these emblems will become increasingly common. According to airbag manufacturer Autoliv, side curtain airbags are available in over 60% of new vehicles in North America and Europe, and that number will continue to rise as side curtains become standard to meet the 2013 side impact regulations [source: Autoliv: Inflatable Curtain].
There are only a handful of major OEM suppliers of side curtain airbags, which results in relatively consistent pricing and slim profit margins for the suppliers. This helps keep costs affordable for car buyers. The price for side curtain airbags ranges from $50 to $100 each, depending mainly on the size of the vehicle [source: Automotive News]. Larger SUVs and crossovers with third-row seating require more expensive airbags due to their larger size and additional deployment modules. According to NHTSA, when side curtain airbags become standard to meet the 2013 side impact regulations, they will add about $33 to the overall vehicle cost [source: Benton].
Side curtain airbags tend to be slightly more expensive from OEM suppliers than traditional chest airbags, which average around $50 apiece [source: Automotive News]. Since automakers often have different ways of 'bundling' safety features, the cost to consumers can vary. While side impact and curtain airbags may occasionally provide extra revenue, most airbag systems are not typically treated as profit-generating sources. Instead, automakers benefit from positive publicity garnered through good safety ratings.
In the upcoming section, we will present some real-world safety tests comparing vehicles with and without side curtain airbags.
Though airbags aren't mandatory in many parts of the world, the global airbag market is still on the rise. A study by Frost & Sullivan estimated that by 2012, airbag accelerometers (the sensors that trigger deployment and detect rollovers) would generate more than $263 million in revenue, up from approximately $200 million in 2002 [source: Venkatesh].
Crash Test Results With and Without Side Curtains
Vehicles come in various configurations to cater to different budgets and needs. For instance, optional airbags may not be a priority for a buyer who seldom carries passengers. If you're considering a particular car, it's important to examine its crash test results. The number of side curtain airbags isn't the only factor to consider – some cars may feature a single airbag covering all the windows, while others may have separate airbags for each window.
We can assess the impact of side curtain airbags on safety ratings by looking at the crash tests conducted by the Insurance Institute for Highway Safety (IIHS) on vehicles equipped with and without side curtain airbags. The IIHS points out that side impact crash test results can be compared across different vehicle types and weight classes, but for simplicity, we will focus on comparisons within the same vehicle model. The rating scale used is: Good, Acceptable, Marginal, and Poor.
To begin, let’s compare the 2002-2006 Toyota Camry without side curtain airbags to the 2004-2006 Camry, which includes side curtains. The difference in model years corresponds to the addition of side curtain airbags in 2004. Although the IIHS refers to the change as 'side structural modifications,' Toyota clarified that these adjustments wouldn't have impacted test outcomes in the absence of the airbags.
The Toyota Camry without side curtain airbags received an overall rating of Poor. Its head protection rating for the driver was Poor, while the rear passenger rating was Marginal [source: IIHS]. In contrast, the Camry with side curtain airbags earned an overall rating of Good, with Good ratings for both the driver and rear passenger head protection [source: IIHS].
For car buyers balancing school runs and soccer practice, the IIHS also tested the 2006-2007 Dodge Grand Caravan. In this case, side curtain airbags significantly enhanced safety for both the driver and passengers. The minivan without side curtains was rated Poor overall, with Poor protection for the driver's head and Marginal protection for the rear passenger's head [source: IIHS]. On the other hand, the minivan equipped with side curtains received an Acceptable overall rating, with Good ratings for both the driver and rear passenger head protection [source: IIHS].
On the following page, you'll find a wealth of information about airbags and other important automotive safety features.
