* The Severity of the Impact: This is the most important factor. The car's speed is a component of this, but the angle of impact, the type of collision (front, side, rear), and the type of vehicle involved all significantly affect the severity. A low-speed, head-on collision might trigger airbags, while a high-speed glancing blow might not.
* The Type of Sensor System: Modern cars use sophisticated crash sensors that measure the acceleration (or deceleration) rate and other factors to determine if a deployment is necessary. Different manufacturers have different systems with varying sensitivity thresholds.
* The Vehicle's Specific Programming: Each car's airbag system is programmed with specific parameters that determine when it should activate. These parameters can vary even among models of the same make and year.
While it's impossible to give a specific speed, it's safe to say that airbags are designed to deploy in moderate-to-high-speed collisions where the risk of serious injury is substantial. This is often significantly *less* than the speed that would cause significant damage to the vehicle itself. In short, there is no magic speed. The system assesses the overall impact severity, not simply speed alone.
