Pedestrian Airbags – Mechanism & Technology

Pedestrian airbags are an innovative safety feature added to vehicles in recent years. They provide a cushion of protection for pedestrians who may be hit by a car.

In this article, we’ll look at the technology behind pedestrian airbags and how they work.

Pedestrian Airbags – Behind The Scenes Of Their Mechanism

Pedestrian airbags have been a welcome addition to the safety features of modern cars.

The airbags are designed to detect when a pedestrian is hit by a vehicle. They then deploy an airbag in front of the person to protect them from injury.

Let’s find out the mechanism behind this advanced safety feature.

1. Sensors & Other Components:

First, the system uses sensors and other components. They detect an impending pedestrian collision.

These sensors detect when a person is in front of the car. It then sends signals to the airbag system.

Cushion of protection for pedestrians - Pedestrian Airbags

The airbags are then triggered to inflate within milliseconds of detecting an impact with a pedestrian.

The airbag inflates with a cushion of air to protect the person from injury. Now there are many factors that the sensors take into account before deploying the airbag:

– Vehicle speed

– Distance between the pedestrian and the car

– Direction of impact

Vehicle speed determines how much cushioning the airbag needs to provide. The greater the speed, the more cushion is needed.

The distance between the car and the pedestrian determines how quickly an airbag is deployed. The closer they are, the quicker it deploys.

The direction of impact will also affect how much cushioning is provided by the airbag.

Pedestrian airbags use sensors in the bumper. They detect when a pedestrian has been hit and then send a signal to the airbag controller.

The controller then activates the inflator to deploy the airbags. Sensors also use other technologies, such as radar and cameras.

They identify when a pedestrian is close to the vehicle. When these are detected, the system will prepare for deployment anticipating an impact.

2. Inflation Process:

The airbag begins inflating as soon as the sensors trigger it. It usually takes less than a second for an airbag to inflate, providing the necessary cushion fully.

Once fully inflated, the airbag absorbs the majority of the impact. It cushions and protects the pedestrian from a collision with the car.

Now a few steps are involved in the airbag inflation and deployment process.

1. First, a sensor in the car detects an impact on a pedestrian. This triggers the release of an inflator inside the airbag module.

2. The inflator then releases hot gases, which inflate the airbag in milliseconds. These gases are usually nitrogen and carbon dioxide.

3. The gases fill the bag with air, which helps cushion the pedestrian from the impact of a collision.

Factors Affecting The Inflation Process:

Many factors can affect the inflation process. These can all affect how quickly and effectively the airbag will inflate:

1. Size Of The Bag:

A larger airbag will provide more cushioning for the pedestrian. A smaller airbag may not fully protect the pedestrian from the impact of a collision.

Some airbags are designed to fit the size of the pedestrian. They inflate differently depending on who is in the car. Others may have a universal size that is suitable for any pedestrian.

2. Type Of Inflator Used:

The type of inflator used can also affect how quickly and effectively an airbag will inflate. Different inflators may have different inflation rates.

They may require a longer or shorter time to fill the airbag. For instance, a pyrotechnic inflator will fill the airbag quickly.

However, it may not be as soft and cushioning as one filled with a gas generator.

3. Pressure Level:

The pressure an airbag is filled to can also affect its performance. Higher pressures can help the airbag cushion impact more effectively.

Lower pressures may reduce the overall protection offered. Also, the pressure with which an airbag is filled will determine how fast it deploys.

Higher pressure levels may help ensure quicker and ultimately safer deployment for pedestrians.

4. Materials Used:

The materials are chosen for the fabric of an airbag vary. They can also influence how cushioning and protective it is.

Materials like nylon, polyester, and Kevlar are often used for pedestrian airbags.

These materials can provide a mild cushioning effect to help absorb the impact of an accident.

5. Deployment Time:

The time it takes for an airbag to deploy is also important. Airbags need to inflate fast enough to ensure pedestrian safety in the event of an accident.

Typically, modern airbags are designed to deploy within 0.08 seconds after impact. This is much faster than traditional airbags, which can take up to 0.2 seconds or more to inflate.

Comparison With Other Airbags:

Pedestrian airbags are different from regular car airbags in a few ways. For example, they use a different material to cushion the impact.

Provide softer cushioning.

Regular car airbags use gas-filled bags that expand rapidly when triggered. Pedestrian airbags use foam or similar materials that expand more slowly and provide softer cushioning.

Also, pedestrian airbags are designed to deploy closer to the ground than regular car airbags. This makes them more effective at cushioning impact with pedestrians.

Types Of Pedestrian Airbags

There are three main types of pedestrian airbags. They all work in a similar way, but each has its own benefits and drawbacks.

1. Hood-mounted Airbags

The first type of pedestrian airbag is hood-mounted. This type typically attaches to the underside of the vehicle’s hood, near the center of the car’s windshield.

It deploys when sensors detect an impact on a pedestrian or other object. The airbag expands quickly and inflates outwards.

This creates a cushion between the pedestrian and the vehicle’s hood. Their size and shape determine their effectiveness and the speed at which they deploy.

Their size is usually large enough to protect a pedestrian. But it is not so large that it obstructs the driver’s view.

The shape is designed to provide the most protection possible while maintaining a low profile.

2. Bumper-mounted Airbags:

The second type of pedestrian airbag is bumper-mounted. Bumper-mounted airbags are located in the front or rear bumpers of a vehicle.

They detect an impact through sensors built into the bumper. They then rapidly inflate when triggered.

The airbag absorbs energy from the impact and protects pedestrians from injury. Their effectiveness is lower than hood-mounted airbags.

Their size is usually too small to provide the necessary protection. Their shape is also designed to provide a lower profile.

With any impact, bumper-mounted airbags can provide some protection.

3. Windshield-mounted Airbags:

Windshield-mounted airbags are located in the upper part of a vehicle’s windshield.

They detect an impact through sensors built into the glass. They then rapidly inflate when triggered.

Unlike hood-mounted or bumper-mounted airbags, windshield-mounted airbags protect drivers, passengers, and pedestrians.

This type of airbag provides better overall protection than other types. It is due to their larger size and increased coverage area.

These make them more effective at protecting pedestrians from head injuries in high-speed impacts.

Windshield-mounted airbags require more expensive hardware than other airbags. It is because they must be mounted to the upper part of the vehicle’s windshield.

Despite this, they are becoming increasingly popular in high-end vehicles due to their superior protection.

The deployment of these airbags is also faster than other types. This provides additional protection in the form of a cushion of air released into the space between the hood and the windshield.

Safety Benefits of Pedestrian Airbags

Pedestrian airbags are designed to reduce the risk of serious injury or death when pedestrians are involved in a collision.

In particular, they are most effective at protecting from head injuries. They do so by providing cushioning between the person and the vehicle.

This allows them to absorb some of the impact energy. This can be especially beneficial in collisions with high-speed vehicles.

There the airbag will help dissipate the energy more quickly than possible.

Automatic Emergency Braking:

Let’s discover how pedestrian airbags work with other safety features.

Automatic emergency braking works by detecting the presence of a person or object in front of the vehicle. And it applies the brakes to prevent a collision.

This feature may get combined with a pedestrian airbag. It provides an extra level of protection for pedestrians.

Some new cars are designed with a special pedestrian airbag system. It is designed to interact with the vehicle’s Automatic Emergency Braking system.

When an individual is detected in front of the vehicle, the pedestrian airbag is automatically deployed and cushions their fall.

Impact On Fatalities & Injuries:

Pedestrian airbags have been proven to reduce fatalities and injuries in pedestrian accidents. According to the National Highway Traffic Safety Administration (NHTSA), pedestrian fatalities have increased steadily in recent years.

Deployed & cushions their fall.

The type of injuries that are best prevented by the airbag system includes:

1. Head Injuries:

The airbag cushions the head, preventing serious injuries such as skull fractures and brain injuries.

Some pedestrians also experience neck and spinal injuries. It can be reduced with the airbag system.

2. Chest Injuries:

The airbag helps prevent injuries to the chest, including broken ribs and internal organ damage.

Chest injuries are the most deadly type of pedestrian injury, affecting the heart and lungs.

3. Lower Extremity Injuries:

The airbag helps prevent serious lower-body injuries. They may be broken legs and hips, which can be especially difficult to recover from.

Although airbags are a helpful form of protection, they are not the only safety feature available.

Limitations And Concerns

Pedestrian airbags are a relatively new technology with some limitations and concerns.

1. Speed Sensitivity:

Pedestrian airbags may not deploy if the car is traveling at speeds below 16 km/h in some cases. This means they could be less effective in preventing injuries in slower-speed collisions.

The airbag may not deploy in slower-speed collisions. But other features, such as automatic emergency braking (AEB), can still be helpful.

They can detect potential collisions and slow the vehicle down before impact.

2. Cost:

Pedestrian airbags can be quite expensive for car manufacturers to install. It could make them inaccessible to some people.

Some cars with pedestrian airbags may be too costly for the average consumer. But you can still find quality vehicles with other safety features that protect a budget.

3. Interference:

Pedestrian airbags could also interfere with some of the other safety features in a car. They may be sensors or cameras.

This means they may need to be placed away from the airbag deployment area for them to remain functioning.

However, most cars with pedestrian airbags also have other safety features. So the risk of interference is minimized.

3. False Sense Of Security:

Some drivers may get a false sense of security when buying a car with pedestrian airbags. They may believe they are fully protected against pedestrian collisions.

It’s important to remember that a pedestrian airbag does not replace the need for other safety features. There must be speed limiters and automatic emergency braking.

These all play an important role in reducing pedestrians’ risk of injury and death.

4. Improper Installation:

Improper installation of a pedestrian airbag can reduce its effectiveness. For example, the airbag is too close to the road.

It may not activate in time to protect the pedestrian from injury. Drivers and mechanics must check the proper installation of the airbag.

They must ensure it is correctly positioned and all components work properly.

5 Dysfunctional Airbag:

Dysfunctional airbags can be dangerous. If the airbag fails to deploy in a collision, it won’t protect pedestrians from injury.

Drivers and mechanics must check the airbag regularly to ensure it functions correctly.

This calls for maintenance and inspection on a regular basis.

We can’t emphasize enough how important pedestrian airbags are to the safety of pedestrians.

They provide an extra layer of protection that can be invaluable in the event of an accident.

 Maintenance And Replacement

Pedestrian airbags require regular maintenance and inspection. Several steps should be taken to ensure the airbag is properly working.

It’s recommended that the airbag be replaced after four years or 80,000 miles of driving.

This varies depending on how much you drive and other factors. But it should not go beyond five years.

The steps for maintaining an airbag are below:

1. Check the airbag pressure and inflation level

2. Ensure the bag is securely in place, with no signs of wear or damage

3. Inspect the wiring and electrical components for any signs of damage

4. Test all safety features

Some of these steps may require the help of a professional.

Cost Of Airbag Replacement:

If it’s time to replace your airbag, you can expect to pay between $500 and $1000 for labor and parts.

Airbags replacement - Pedestrian Airbags

This cost varies by vehicle. So be sure to ask your mechanic for the exact amount before starting work.

It’s always important to ensure that your car is safe and secure. So replacing your airbag or having it inspected periodically is essential.

Replacement Process:

The process for replacing a pedestrian airbag is quite straightforward:

1. Disconnect the battery to avoid any accidental deployment of the airbag.

2. Remove the old airbag and all associated components from the dashboard.

3. Install the new airbag, connect it properly, and test its functionality.

4. Reattach all other components, such as any trim pieces or screws

Although replacing your pedestrian airbag might take an experienced mechanic, the process is relatively simple.

Recommended Replacement Interval:

Having your pedestrian airbag inspected at least once a year would be best. Or has it been checked after any accident involving the car?

If necessary, you should replace it immediately if there is any sign of damage. Additionally, the airbag should be replaced after 4-5 years to ensure it is in good working condition.

Future Developments:

Automakers are continuously looking for ways to improve pedestrian airbag technology.

Research and development efforts currently focus on incorporating advanced sensors.

They are also deploying airbags with new materials, so they can better cushion the impact of an accident.

These advancements are expected to become more widespread in the near future. Thus, invest in regular inspections and replacing airbags when necessary.

You can ensure the best kind of protection for pedestrians. It is also worth noting that many automakers are expanding their technical scope.

They are looking at alternative solutions, such as exterior airbags and advanced emergency braking systems.

These technologies could replace standard airbags in certain scenarios as they become more effective.


To conclude, pedestrian airbags are an important development in automotive safety. They have the potential to save lives and reduce serious injuries due to collisions.

As technology advances, we can expect airbags to become even more sophisticated and effective.

They are not a substitute for safe driving practices and other forms of automotive safety equipment.

But they provide an invaluable extra layer of protection. In addition, airbags have the potential to help vehicles absorb impact and reduce the severity of crashes.

It can make a life-saving difference in an emergency situation.

The development of pedestrian airbags is a significant step forward for automotive safety. It can potentially save countless lives.

About the author

David Englert is a 40-year-old mechanic specializing in airbags. With years of experience in the field, he has developed a deep understanding of the intricate workings of airbag systems. He is highly regarded in the industry for his expertise and attention to detail.

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