How do we promote safe driving behaviors without nagging?

TL;DR

I designed a warning experience that reminded the drivers to keep their hands on the wheel.

After the executive demonstration, I was told my warnings were noticeable, but not distracting, reaffirming, but not nagging.

My Roles

  • Defined functional requirements
  • Iterated on experience flows
  • Expanded notification framework
  • Built new UI components

Problems

When the car is in advanced driver assistance mode, it is tempting for the driver to let go of the wheel and rely on the automation extensively.

However, this is not what today’s assisted driving features were designed for. It is also against the law to allow level 2 automated driving feature continue without constant driver input.

Objectives

Design a warning experience for when the car detects the driver does not have his or her hands on the wheel.

Existing Notification Framework

Previously, I defined an in-vehicle notification system that included multiple levels of warnings across different communication modals. For this project, these were the relevant warning components.

Warnings on Center Display

The Center Display can accommodate 3 levels of visual warnings.

Warnings on Driver Display

The Driver Display has 1 level of visual warning.

Warnings on Head-up Display

The Head-up Display has 1 level of visual warning.

Warnings via acoustic

The sound library has 3 acoustic warnings.

Audio samples are not included in this case study. I did not design the audios.

Solutions

Initial Solution – Follow the Framework

Our development team applied the obvious solution according to my existing notification framework. When the driver took his or her hands off the steering wheel, a visual warning appeared on the driver display, and mid level acoustic warning plays.

Learnings

Drivers found this warning experience too aggressive. Often, they did not take their hands off by accident. They simply wanted to relax for a few seconds while Auto Steering feature remained in control.

I wanted to empower this driver behavior.

New Strategy – Escalating Warnings

First, a delay trigger was added to allow the driver a few seconds of relaxation without any warning at all. After that, a low level warning experience gently reminded the driver, and allowed the option to easily ignore the warning experience. Lastly, a lasting high level warning strongly reminded the driver until the driver’s hands were detected again.

Learnings

This revision was appreciated by the drivers, but they felt the high level warning still came too quickly. Also, I learned the law required the car to turn off the assisted driving feature if the drivers did not return their hands after 60 seconds.

Final Solution – Refined Escalating Warnings

After several rounds of adjustments, I added a new tier, and lengthen the time to trigger each tier. The highest level of warning would trigger when the assisted driving feature was turned off.

Learnings

The drivers felt comfortable with this timing and warning intensity, and legal team approved my design.

New UI Components

This problem was specifically relevant to the driver, and I felt it was necessary to use the Driver Display as the primary visual communication channel for all 3 levels of warning. This meant I needed to introduce additional levels of visual warning components for the Driver Display. The new components would also be used to better organize other existing driver warnings.

Copywriting

The steering wheel sensor needed to detect a slight resistance in the torque in order to detect the driver’s hands. Also, my copy needed to make sure the driver did not apply too much resistance, or the automated features would deactivate.

I used the words “gently” and “nudge” as double instruction for the driver.

Experience Flow

Low Escalation Warning

In this level, the system gently warns the driver after he or she took the hands off the steering wheel for 15 seconds. No acoustic warning meant the driver’s attention would not be disrupted.

15 sec after letting go of the wheel

Driver Display
low level warning
blue flashes every 1 sec

Mid Escalation Warning

In this level, the system triggers an urgent experience after the driver took the hands off for a total of 30 seconds. A continuous acoustic chime would demand the driver’s attention.

30 sec after letting go of the wheel

Driver Display
mid level warning
blue flashes every 0.5 sec

Center Display
mid level warning

Acoustic
mid level warning

High Escalation Warning

This is the final level. After a total of 60 seconds without hands on the wheel, the car is required by law to deactivate both Adaptive Cruise and Auto Steering features. The driver must reengage the driving task to prevent the car from rolling to a stop.

60 sec after letting go of the wheel

ADAS Feature
deactivates

Driver Display
high level warning
hazard lights

Center Display
high level warning

Head-up Display
high level warning

Acoustic
high level warning

Impacts

Executive Buy-in

I monitored the feedbacks from internal users throughout the project, and adjusted the design continuously. I was glad my final demo to senior leadership resulted in praises. I was told the warnings were noticeable, but not distracting, reaffirming, but not nagging.

Future Considerations

I recommended the team to consider hardwares for haptic feedback and developments for speech feedback. Both of these would allow eyes-free communication to the driver.