SRS System Description - Overview
The vehicles are equipped with SRS airbags (driver's and front passenger's), side airbags, side curtain airbags, and seat belt tensioners.

i-SRS Airbag System (Driver's and Front Passenger's Airbag)
In case of a frontal collision, the i-SRS airbag system uses a seat belt tensioner as a body restraint device in addition to the impact-absorbing construction of the body shell as a function to mitigate the impact forces acting on the head and chest of the front seat occupant. The driver’s airbag and the front passenger’s airbag use two inflators for a dual-stage output control system. In case of a collision at low or medium speed, the airbag is deployed while reducing the inflator output by means of a dual-stage ignition of each inflator, which helps to reduce the possibility of injury to the occupant. In case of a sudden collision at high speed, both inflators are ignited at the same time to restrain and protect the occupants. The system registers when a seated occupant is wearing the seat belt, and in some cases, like a low-speed collision, the occupant may be restrained by the seat belt only. For improved protection of the occupant and for reduced impact force of the airbag, the driver's airbag is a type with continuously variable volume.

Operating Process of the SRS Airbag
1.
The impact force generated by frontal collision is transmitted via the vehicle's structural components, and input to each of the front impact sensors, the front impact G sensor, and the safing drive circuit inside the SRS unit.

2.
The front impact sensor converts the collision to electrical signals, which are sent to the microprocessor and the safing drive circuit inside the SRS unit. At the same time, the front impact G sensor inside the SRS unit converts the collision input into waveform electrical signals, and sent to the microprocessor.

3.
The microprocessor outputs actuation signals if the outputs from the front impact sensors and front impact G sensor exceed the preset threshold value. At this time, if the output from the safing drive circuit inside the SRS unit exceeds the preset threshold value, current flows through a trigger circuit, which deploys the SRS airbag, and operates the seat belt tensioner.
Conditions of SRS Airbag Deployment
Frontal collision against rigid wall:

In the case of a frontal collision against a rigid wall, like a concrete wall, the SRS airbag may deploy when the vehicle reaches 12 mph (20 km/h). The airbag may not deploy at that speed in all cases because of other inputs.

Frontal collision between vehicles:
In case of a frontal collision between vehicles at the vehicle speed more than about 12-19 mph (20-30 km/h), the SRS airbag deploys.
In case of a frontal collision between a moving vehicle or a parked vehicle, the SRS airbag deploys at twice the speed (more than about 25-37 mph (40-60 km/h)). The deployment condition varies depending on the vehicles in question and the collision state such as angle.
SRS Airbag Does not Deploy in the Following Cases:
The SRS airbag deploys when a strong impact comes from the front right or left direction within 30 degrees from the front face when the vehicle is in the ON mode. Therefore, in the following cases, the SRS airbag does not deploy because there is no effect on the occupant protection. Note that it may deploy depending on the state of collision.

SRS Airbag May Not Deploy in the Following Cases:
The deployment of the airbag is designed based on the scale of the impact brought to the occupant. Therefore, the deployment of the SRS airbag is not always related to the degree of damage to the vehicle.

Side Airbag System and Side Curtain Airbag System
In case of a side impact, the side airbag, the side curtain airbag, and the seat belt tensioner on the impact side operate in addition to the impact-absorbing body shell of the vehicle, which mitigates the impact forces acting on the head and chest of the occupant. Moreover, the left and the right side impact sensors detect the various states of collision, so that the airbag deploys accordingly. The side airbag uses a variable volume type; the construction and the deployment process of the airbag pressure chamber have been improved, and enable a safe deployment regardless of the position of the occupant. Therefore, conventional OPDS* related parts are not equipped.
*OPDS: Occupant Position Detection System

Side Airbag and Side Curtain Airbag Deployment Process
1.
The collision force generated from the side impact is input to each of the side impact sensors and the side impact G sensor inside the SRS unit.

2.
If the microprocessor inside the SRS unit determines that the side impact sensor output exceeds a preset threshold value, and if the output from the side impact G sensor inside the SRS unit exceeds a preset threshold value, the circuit creates an actuation signal.

3.
The actuation signal is sent from the microprocessor to the trigger circuit, which deploys the side airbag, the side curtain airbag, and the seat belt tensioner.
NOTE: In case of a strong frontal collision the threshold value for a side impact is exceeded in the SRS unit, the side curtain airbag may deploy.
Side Airbag and Side Curtain Airbag Deployment Conditions
When the vehicle is subject to strong side impact, and the side impact G sensor detects an impact that exceeds the preset threshold value. The side airbags and side curtain airbags on the side receiving the impact will deploy.

NOTE: The side curtain airbags may deploy along with the front airbags during a front-end collision in order to protect the heads of occupants if the collision force to the side of the vehicle exceeds a certain value.

Conditions in which Side Airbag and Side Curtain Airbag may not Deploy
Since the side airbags and the side curtain airbags are designed to deploy when impact force to vehicle side exceeds a preset value, they may not deploy when impact forces are reduced by the vehicle's crush zone, or when a side impact is applied in the front or behind the passenger compartment. Also, these airbags may deploy in the case of side slip collision or when the vehicle roll overs, but in such cases will not provide full occupant protection.

Seat Belt Tensioner
The seat belt tensioner instantaneously retracts the seat belt at the time of a collision, and the effect of the seat belt is increased further by securely restraining the occupant in the seat. In the case of a low to medium speed or high speed collision, the airbags and the seat belt tensioner are activated to secure the restraining effect of the occupant and the safety performance. In the case of a low-speed collision, the seat belt tensioner operates alone because occupant restraint can be secured by the seat belt only.