Supplemental Restraint Systems 5

5 Knowledge Objectives (1 of 2) Explain what a supplemental restraint system consists of. Explain the difference between an active restraint device and a passive restraint device. Explain the air bag deployment process. Explain the basic components that make up an air bag system.

5 Knowledge Objectives (2 of 2) Describe a roll-over protection system and how it is activated. Describe a seat belt pretensioning system and how it is activated. Explain the emergency procedures for handling vehicles equipped with air bags.

5 Introduction In 1967, the National Highway Traffic Safety Administration (NHTSA) issued Federal Motor Vehicle Safety Standards (FMVSSs). – To protect the public from risks of injury or death resulting from poor design, construction, or performance of a motor vehicle.

5 Supplemental Restraint Systems (1 of 14) In the 1970s, vehicle fatalities rose because people were not wearing seat belts. The air bag emerged and became known as a supplemental restraint system (SRS). © dpa/Landov

5 Supplemental Restraint Systems (2 of 14) Manual seat belts are an active restraint device. Air bags are passive restraint devices. In 1984, FMVSS 208 was amended to mandate that motor vehicles must be equipped with a passive restraint system.

5 Supplemental Restraint Systems (3 of 14) First air bags were only fitted for average males. – FMVSS was amended again to require accommodations for differently–sized individuals. All vehicles made after September 1, 2006 are required to have smart air bag systems. © Insurance Institute for Highway Safety/AP Photos

5 Supplemental Restraint Systems (4 of 14) Smart air bag systems automatically adjust the pressure in the air bag by using inflators. – Deployment force is based on: Crash severity Occupant’s weight Proximity to the air bag Seat belt usage Seat position

5 Supplemental Restraint Systems (5 of 14) Features to protect occupants from air bag injuries: – Dual–stage or multi–stage inflation process – Suppression system shuts down air bag if occupant classification system detects a child.

5 Supplemental Restraint Systems (6 of 14) Air bag deployment process: – Crash itself – Crash sensor (accelerometer) detecting deceleration – Air bag deploying and inflating – Occupant moving forward and striking the bag as deflation occurs

5 Supplemental Restraint Systems (7 of 14) Air bag components – Air bag Durable nylon or blended material Coated with powdered substance Cover is designed to tear apart when inflated. Size of bag will vary.

5 Supplemental Restraint Systems (8 of 14) Air bag components – Air bag (cont’d) Side–impact air bags Knee air bags Seat belt air bags Rear seat systems Outside pedestrian protection system

5 Supplemental Restraint Systems (9 of 14) Air bag components (cont’d): – An initiator device, such as a squib, ignites the propellant that produces the gas that fills the air bag.

5 Supplemental Restraint Systems (10 of 14) Air bag components (cont’d): – Electronic control unit (ECU) Calculates the level of deployment needed to protect the occupants Energy capacitor acts as a back- up system Some record and store information from accidents

5 Supplemental Restraint Systems (11 of 14) Air bag components (cont’d): – Inflator Fills ups air bag instantaneously Positioned in cut zone areas Stored compressed gas system uses inert gas stored in steel or aluminum cylinder

5 Supplemental Restraint Systems (12 of 14) Air bag components (cont’d): – Inflator Multistage inflators are cylinders comprised of two separate chambers of compressed gas. Gas generation system uses a chemical reaction that rapidly produces the gas that fills the bag.

5 Supplemental Restraint Systems (13 of 14) Air bag components (cont’d): – Sensors Sends information to the ECU. Detects a rapid deceleration of the vehicle. Several different types can be located in a vehicle.

5 Supplemental Restraint Systems (14 of 14) Air bag components (cont’d): – Occupant classification system Seat position sensor (proximity of the occupant to the air bag) Seat belt sensor (engagement of seat belt) Occupant weight sensor (determines whether the occupant has met a preset weight)

5 Roll–Over Protection System (1 of 2) Roll-over protection systems (ROPS) were initially designed for convertible vehicles. – Concealed until activated – Activated by an inclinometer sensor or tilt sensor – Gravitational acceleration sensor (G-sensor) detects a vehicle’s weightlessness To activate, sensors must detect a significant vehicle tilt with lateral acceleration

5 Roll–Over Protection System (2 of 2) Exercise caution when operating around a vehicle containing an undeployed roll bar. Follow the same safety guidelines and electrical disconnection procedures for air bag systems. Courtesy of Volvo Cars of North America, LLC

5 Seat Belt Pretensioning System (1 of 2) A seat belt pretensioning system automatically tightens or takes up slack when a crash is detected. – Operates at: Belt buckle attachment Anchor attachment

5 Seat Belt Pretensioning System (2 of 2) Seat belt assemblies can be housed in any post or column, under the seats, or in the center console. Concept of dissection underlies the processes discussed in this chapter.

5 Emergency Procedures (1 of 5) Never assume the air bag is dead. – Energy capacitor can store power for 30 minutes. – Air bag inflators are “live” until deployed. – Attempting to disable the inflator can cause the air bag to deploy. Licensed technicians must install, repair, or remove air bags.

5 Emergency Procedures (2 of 5) Several things can be done to ensure that power is disconnected. – Remember there is a backup energy system with storage capacitors. – Remember it may be difficult to adjust seats if beneficial systems are installed in the vehicle.

5 Emergency Procedures (3 of 5) Recognizing and identifying air bags – Common acronyms: SRS SIR HPS SIPS ROI – Scan interior for locations

5 Emergency Procedures (4 of 5) Recognizing and identifying air bags (cont’d) – Once the air bag has been identified, maintain proper distance from the deployment zone. 10 inches for driver’s side 20–25 inches for passenger side 5–15 inches for side impact bags

5 Emergency Procedures (5 of 5) Extrication precautions – Properly disconnect the power. – Never place anything between patient and undeployed air bag. – Never tie up an air bag. – Inspect before you dissect! – Consider the ECU location. – Be aware of side-impact sensors.

5 Summary (1 of 4) In 1967 the NHTSA issued a mandate outlining minimum safety requirements for vehicles. In the 1980s, the air bag became known as a supplemental restraint system (SRS) by working in conjunction with the seat belt. Manual seat belts are classified as an active restraint device because the occupant has to activate the system by engaging the seat belt mechanism into the anchor unit.

5 Summary (2 of 4) A vehicle air bag is classified as a passive restraint device because the occupant does not have to activate it to make it function. Smart air bag systems are using adaptive response features such as dual-stage or multistage inflation and suppression systems. A four-stage process occurs when an air bag deploys in a crash sequence.

5 Summary (3 of 4) Several components make up an air bag. Roll-over protection systems (ROPS) were initially designed for convertible vehicles. Seat belt assemblies can be housed in any post or column, under the seats, or in the center console. The molding must be removed to reveal the pretensioning system in order to cut around the device.

5 Summary (4 of 4) Never assume that an air bag is dead just because the power has been disconnected; a vehicle air bag system comes equipped with an energy capacitor. Eliminating potential hazards of SRS systems may include disconnecting power, recognizing and identifying air bags, distancing, and following certain rules.