In-cabin sensing technology senses the driver and occupant condition to ensure a better protected and more comfortable driving experience. Per AAA, an American automative trade group, 800 drowsy-driving-related fatalities are reported yearly. Additionally, 65% of truck drivers reported that they often feel drowsy while driving. Fatigue and other human factors are driving the research and adoption of

Depending on the interior monitor system, varying aspects are evaluated, from body gestures to head position. Eyelid movement and pupil tracking are also common in today’s technologies; for example, lip movement -- to indicate yawning — is being added as a variable in upcoming equipment. By monitoring the cabin, these advancements detect fatigue, distraction and passenger occupancy for increased safety.

Drivers are also understandably wary about vehicle occupant monitoring. Cars are in many ways shaped by individuality. They are akin to an outfit, with the fashion choices analogous to color, bumper stickers and hundreds of other accoutrements. They are also a mobile retreat and can feel more like an extension of the home than a machine.

But as cabin sensing technologies expand, they can quickly become invasive and a privacy risk. Erratic driving can be penalized with increased insurance rates, which seems fair. Penalties for visiting certain destinations or listening to certain music seem like a step too far. It has garnered the attention of the U.S. Federal Trade Commission, although they have yet to issue regulation.

As the technology evolves, there’s the potential to monitor more biometrics to the point of detecting if an occupant is suffering from a major medical condition, such as a heart attack. In the future, these technologies will be integral in autonomous vehicle software, allowing for hands-free travel across the country.

In-cabin sensing trends

Many of the top automakers have started implementing vehicle interior sensors for a variety of purposes. Here are some of the most popular trends occurring in today’s vehicles.

Biometric monitoring

Biometric sensors are used to monitor the health metrics of drivers and passengers. These metrics often include driver drowsiness, stress levels and heart rate. Physiological measurement will include sensors to monitor skin conductance, head movements and muscle activity, all of which give the system a broader picture of driver well-being. For example, the systems can measure the number of times a driver blinks to determine if they are becoming drowsy and compare that with lane deviations (Lane Assist) to tell if there’s less focus on the road.

Contextual awareness

AI systems and sensors interpret environmental factors (temperature, humidity, sunlight intensity, etc.) within the cabin to adjust settings for increased safety and comfort. Advanced climate control systems and personalized infotainment systems are examples of this technology. Another example is how some cars can alert the driver to the presence of an emergency vehicle, if the car suspects driver is unaware.

Gesture recognition

Hands-free operation has moved beyond voice control to using gestures. This permits a driver to cue an action from the vehicle without averting their eyes to find a button or operated a screen. Many of today’s vehicle functions, such as navigation, the infotainment system and climate control, now correlate with hand and body movements. With sensors placed in the dashboard or steering wheel, the system constantly monitors the driver for hand movement. When it senses a related command, the information is transmitted to the processor for the driver’s wish to be carried out.

Seat occupancy sensors

Occupant detection technology ensures pets and children aren’t left in the vehicle after the doors lock. There are also advanced systems that determine the weight of the occupant for customized seatbelt pretensioner settings and airbag deployment, ensuring maximum safety in the event of an accident.

OEMs offerings today

ADAS technology helps drivers become more aware of their surroundings and change bad behavior that could lead to a crash. Several reports have already been written to prove the effectiveness of these systems. First, the European Transport Research Review published in 2024 that driver drowsiness monitoring with adaptive lighting systems could reduce fatalities, as these systems promote alertness behind the wheel and improve visibility. Another 2023 study followed commercial drivers; it found that over time, driver behavior changed as a result of receiving alerts from the interior environment sensors.

Several automakers have already implemented the driver and passenger monitoring systems. One of the most known is the Tesla Autopilot System, which uses several sensors and cameras to monitor driver attention and enhance safety during semi-autonomous driving. According to Tesla, during one quarter in 2022, there was one crash for every 4.85 million miles driven using Autopilot technology. Drivers not using Autopilot technology incurred one crash for every 1.4 million miles driven.

Mercedes-Benz also has the Attention Assist technology that monitors lane position, vehicle speed and driver steering behavior to watch for signs of drowsiness. Hyundai uses a rear occupant alert system, which utilizes ultrasonic sensors to detect movement in the rear seat after the doors have been locked. If a pet or child is left behind, the driver is alerted.

Additionally, several manufacturers have implemented gesture and voice controls for entertainment and comfort purposes. BMW has a gesture control system working with the iDrive infotainment to control volume, navigation and phone connections without touching the screen. Select Ford vehicles now use Amazon Alexa integration with voice commands.

Technical challenges to in-cabin monitoring

One of the biggest pushbacks about vehicle interior surveillance is the privacy concerns. While safety is the motivation for these technologies, it’s still important for manufacturers to respect the privacy rights of individuals. Technologies must have robust encryption, easy-to-understand consent mechanisms and data anonymization that protects sensitive information. The in-car sensor technology also opens the door for hacking and exploitation. Advanced protections need to be rolled out and continuously updated to prevent intrusion.

Another concern is the reliability and accuracy of the sensors. It’s possible for the systems to falsely detect signals or conditions in the cabin. To prevent this issue, manufacturers need to test the systems in various environmental conditions, changing light situations and a wide range of temperatures to ensure integrity. There will also need to be regular inspection and calibration of these instruments, as well as protocols for when they break.

Regulatory compliance is another concern as the systems needs to undergo enough testing to prove they meet safety standards and various performance metrics. Each country will set its own requirements and it could be difficult for manufacturers to please every region, just as it is today with parameters such as emissions and safety.

Finally, there’s the cost and scalability aspect to consider. Interior behavioral monitoring comes at a cost for the hardware, software and development. Updates and regular refinement will also be necessary. To achieve a level of cost-effectiveness while scaling it on a broad scope could be challenging.

Future technology for in-car monitoring

In upcoming years, in-car biometric systems will be able to calculate more than the physical health of a driver but also their emotional state. Artificial intelligence-driven systems will analyze facial expressions and voice tone to determine the emotional well-being of the driver. From there, the vehicle settings can be altered based on driver attentiveness. Or if it has just been a rough day, maybe the car cues the driver’s favorite artists and enhances the lighting for a more pleasant cabin.

More regulations should pass in the coming years that use driver monitoring software to prevent impaired operators from getting on the road. For example, the NHTSA has requested a Federal Motor Vehicle Safety Standard for new cars to include a sensor system for detecting if the potential driver is impaired or drunk before starting the engine.

Driver monitoring has become a top concern for automotive engineers due to both social and political influences. Engineers need to plan for these systems by conducting extensive testing, thereby ensuring compliance, accuracy and reliability. However, by embracing the challenges ahead, engineers can create an automotive future that’s drastically safer than the present.

About the author

Brian Jones is an ASE Certified Master Technician and owns a small business in the automotive industry. He is also an experienced technical writer.