Toyota bZ4X Owner's Manual: Emergency Driving Stop System – Advanced Emergency Deceleration & Control

The Emergency Driving Stop System is an advanced safety feature designed to automatically decelerate and bring the vehicle to a safe stop within its lane if the driver becomes incapacitated-for example, due to a medical emergency or other unforeseen events. This system plays a critical role in mitigating collision risks by taking control when the driver is unresponsive.

During LTA (Lane Tracing Assist) Control

When the system operating under LTA control fails to detect essential driving inputs-such as when the driver is not holding the steering wheel-the vehicle is gradually decelerated and brought to a complete stop within its current lane. This controlled stop is intended to avoid collisions or at least reduce the severity of an impact.

WARNING

For Safe Use

• Driving safely is solely the responsibility of the driver. The Emergency Driving Stop System is engineered to support the vehicle in emergency situations (e.g., if the driver suffers a sudden medical crisis) but is not meant to substitute for attentive and proactive driving.
• Although designed to decelerate the vehicle safely within its lane, the system’s performance can vary with different road, weather, and sensor conditions. Always ensure that operating conditions are met and never rely exclusively on this function.
• If the system is activated and then conditions improve, the driver must immediately resume control or, if necessary, safely park the vehicle on the roadside, activate hazard lights, and set up a warning reflector or flare to alert oncoming drivers.
• This system monitors driver responsiveness via steering wheel input. It may activate even if the driver is lightly leaning on the wheel, and it might not work as intended if the driver monitor sensor is impeded.
• Situations where the driver monitor may not perform accurately-for instance, due to unusual postures or if the driver is momentarily distracted-can affect system performance.

System Operation and Control States Summary

The Emergency Driving Stop System operates in four distinct control states to ensure that the vehicle is safely managed if the driver becomes unresponsive:

• Warning Phase 1: After the initial hands-off steering warning, a buzzer sounds intermittently and a visual message is displayed. During this phase, the system evaluates whether the driver regains control by holding the steering wheel or applying the brakes.
• Warning Phase 2: If no driver input is detected within a preset time, the system escalates the warning with more rapid buzzer sounds and intense visual alerts, while initiating a slow deceleration.
• Deceleration Stop Phase: Upon confirming that the driver is unresponsive, the system continuously issues audible warnings and decelerates the vehicle smoothly until it comes to a complete stop. Brake lights may activate during this phase as an extra safety measure.
• Stop Hold Phase: Once the vehicle has stopped, the parking brake is automatically engaged. The system stays in the stop and hold phase with continuous buzzer alerts and flashing hazard lights to warn nearby traffic, keeping the vehicle in a secure state until manual intervention occurs.

Operating Conditions

This system becomes active only when all the following conditions are met:

• The Lane Tracing Assist (LTA) is engaged.
• The vehicle speed is approximately 30 mph (50 km/h) or more.

Operation Cancelation Conditions

The emergency stop system will cancel its operation automatically under these conditions:

• If LTA control is canceled, such as by pressing the LTA switch.
• If the dynamic radar cruise control is canceled.
• If the driver performs any manual operation (e.g., holding the steering wheel, pressing the brake or accelerator pedals, engaging the parking brake, using hazard lights, or operating the turn signals).
• If the driving assist switch is pressed while in the stop and hold phase.
• If the vehicle’s power switch is turned from ON to OFF.
• Or if one or more functions of the system are determined to be inoperative.

LTA Control Considerations When Operation Is Canceled

If the Emergency Driving Stop System operation is canceled for any reason, the Lane Tracing Assist control may also be canceled, fully restoring manual driver control.

Warning Phase 1: Initial Alert

Should the system fail to detect driver input after the hands-off warning activates, it enters Warning Phase 1. During this phase, an intermittent buzzer sounds and a warning message is displayed to determine if the driver becomes engaged.

Vehicles equipped with a driver monitoring camera might immediately commence Warning Phase 2 depending on the sensitivity of the sensor and the nature of the driver’s unresponsiveness.

Warning Phase 2: Escalation

In Warning Phase 2, buzzer alerts intensify through rapid, short intervals, and the vehicle begins to decelerate more noticeably. A visual warning continually prompts the driver to take control, and if no response is registered within a critical period, the system proceeds to the deceleration stop phase. During this time, the audio system may be muted to focus the driver's attention on the alerts. Brake lights can also illuminate as additional signals of imminent stopping.

Deceleration Stop Phase

Once Warning Phase 2 confirms driver unresponsiveness, the system activates the Deceleration Stop Phase. In this phase, a continuous buzzer warning is issued while the vehicle decelerates slowly yet decisively until coming to a complete stop. Immediately after stopping, the system transitions to the Stop Hold Phase.

Stop Hold Phase

After the vehicle has stopped, the system engages the parking brake automatically and remains in the Stop Hold Phase. During this phase, the buzzer continues to sound in a continuous loop, and the hazard lights flash persistently. This not only secures the halted vehicle but also alerts surrounding drivers to the emergency situation. Certain functions of the vehicle may remain restricted until the EV system is re-started.

By integrating advanced sensor technology and proactive driver monitoring, the Emergency Driving Stop System significantly enhances vehicle safety by ensuring rapid, controlled deceleration during emergencies. This system-offering robust protection and clear alert signals-serves as a pivotal component within a comprehensive suite of driver assistance technologies found in modern vehicles. Its innovative design is exemplified by features in the Toyota bZ4X.