The Importance of Camera Placement in Driver Monitoring Systems.

The EU General Safety Regulation 2019/2144 mandates that all new vehicle models receiving type approval from July 2024 onwards must be equipped with advanced driver monitoring systems (DMS) capable of detecting driver inattention—whether due to distraction or drowsiness. By 2026, this requirement will extend to all new vehicles sold across the EU.  

These systems are designed to monitor drivers in real time, utilizing cameras and sensors to analyze key indicators such as eye movement, head position, or blinking patterns. However, the effectiveness of these systems does not just rely on advanced software; the physical placement of the cameras within the vehicle is crucial. Improper positioning can lead to incorrect alerts or missed signs of inattentiveness, potentially undermining the very safety and compliance goals these regulations aim to achieve. 

Finding the right spot for the camera is a delicate balance of technical considerations and practical limitations. Therefore, automakers must carefully consider where to install these cameras to ensure optimal monitoring while balancing various design constraints and driver comfort. In the following sections, we will explore the importance of camera placement and why finding this "sweet spot" is essential not just for regulatory compliance but also for improved road safety. 

While the dashboard and vehicle interior may appear to offer several potential mounting spots for the driver monitoring system camera, each position comes with its own set of challenges—ergonomic, technical, or practical. One of the most used locations is the steering wheel column, which often provides a direct, centrally aligned view of the driver’s face. On paper, this seems like an ideal choice for accurate detection because it places the camera in a strategic position that can closely monitor critical facial elements like eye movement, head position, and blinking patterns. However, real-world usage reveals notable challenges with this setup. 

One of the main problems with mounting the camera on the steering column is that the driver’s hands can easily obstruct the camera’s view, particularly when they place one or both hands at the top of the steering wheel. This is a fairly common behavior among many drivers, particularly during long stretches of highway driving or when navigating through tight corners or long arcs. When a hand rests on the upper part of the wheel, the camera’s field of view can become partially or completely obstructed, rendering the system ineffective in monitoring the driver's facial features and eye movements.  

Worse still, on highways or during prolonged turns where hands linger at the top of the wheel for extended periods, the DMS might fail to detect key signs of inattention just when they are most needed. Therefore, while this position allows for a clear frontal view under ideal conditions, it can become significantly compromised when real driving behaviors come into play. 

 Figure 1. Obstruction caused by drivers' behavior. Source: ROBOTEC.AI. 

On the other hand, some manufacturers explore placing the DMS camera in locations such as the A-pillar (driver’s side) or near (and even within) the rearview mirror, each offering its own set of advantages and drawbacks. From our experience with DMS systems, we know that both positions might increase the likelihood of triggering false-positive alerts, especially in real-world driving conditions where drivers frequently move their heads to check their surroundings or briefly glance at the dashboard.

It is worth pointing out that it is crucial for the selection of the DMS position to be tested together with the software dedicated to the setup, as some of the problems generated by the physical location of the sensor in the cabin can be mitigated by the algorithm. At the same time, it must be reckoned that even the best algorithm will not overcome all the problems generated by the sensor location. 

In the case of the A-pillar, the mounting position offers a side view of the driver, which, while capturing some body posture in addition to facial cues, provides a limited vantage point for tracking critical elements like eye movements and blinking patterns. The system might be prone to misinterpreting typical driving behavior—such as side looks—as signs of inattention. For instance, when the driver performs necessary checks on surrounding traffic, the system may mistakenly interpret these actions as the driver closing their eyes or diverting their focus from the road. This could result in unwarranted alerts for behavior that is, in fact, safe and appropriate. Such false positives may decrease the perceived reliability of the system, leading to user dissatisfaction due to frequent, unnecessary warnings. 

On the other hand, the rearview mirror position offers the benefit of a more centralized, frontal view of the driver’s face, which is advantageous for maintaining consistent tracking of head orientation and eye movements. However, even in this position, there are susceptibility risks regarding false-positive detections, especially when the driver glances down to check the speedometer or navigational prompts.  During such events, the system might misinterpret these actions as signs of driver inattention. This can lead to the system triggering inappropriate warnings when, in reality, no immediate risk is present. 

A notable advantage of rearview mirror mounting is the potential for hardware integration with other OEM (Original Equipment Manufacturer) sensors or Occupant Monitoring Systems (OMS). The rearview mirror area is often a central hub for both DMS and various OMS functionalities, such as monitoring the presence and behavior of passengers (e.g., seatbelt usage, child-seat detection, or even occupant movement). By integrating DMS and OMS into a single camera, manufacturers could potentially reduce hardware costs and streamline system complexity. This approach could offer significant savings in terms of wiring, sensor installation, and calibration. The simplicity of using one versatile camera for multiple monitoring tasks can lower vehicle production expenses while providing advanced, multi-functional safety systems to consumers. 

However, this integration does raise some technical challenges. A wide-angle camera becomes necessary to monitor both the driver and vehicle occupants. A wide-angle lens is designed to cover a broader field of view, allowing it to capture both the driver’s face and the entirety of the cabin. While this offers a practical solution for combining DMS and OMS functionality in a single unit, wide-angle cameras are more prone to image distortion at the edges of the frame, which can reduce the overall accuracy of the system. 

For driver monitoring systems, precision is critical, especially when tracking subtle facial movements such as eye blinks, gaze direction, and head tilt—elements that are vital for detecting distraction or drowsiness. When using a wide-angle lens, image distortion can alter the appearance of the driver’s face, skewing the system’s ability to accurately monitor these facial cues. For example, at the periphery of the camera’s field of view, important features such as the driver’s eyes might appear stretched, or other facial details might become less defined—a limitation that could affect the system’s ability to correctly interpret the driver’s state. This loss of precision could result in misdiagnosing driver behavior, exacerbating issues like false-positive alerts or missed signs of drowsiness. 

Moreover, the wide-angle camera would need to reliably switch focus between monitoring the driver’s face and tracking occupants’ positions or behaviors in the back seat. Managing these two functions simultaneously could stretch the camera’s processing capacity, leading to conflicts or delays in data interpretation. The overall system would face significant challenges in balancing the dual demands of tracking both drivers and passengers without compromising the safety of either. For instance, prioritizing rear-seat occupant monitoring could reduce the camera’s available resources for real-time driver monitoring, increasing the likelihood of missed danger signals. 

Combining Multiple Camera Setups for Greater Accuracy 

A promising way to enhance Driver Monitoring Systems (DMS) is by using a combination of cameras positioned in multiple locations, such as pairing a steering wheel column camera with one mounted on the A-pillar or rearview mirror. By capturing the driver’s face from several angles, this setup can overcome issues like obstructed views caused by hand placement or natural head movements. In situations where one camera’s view is blocked, another can seamlessly take over, ensuring consistent tracking of drowsiness or distraction. This multi-angle approach also allows the system to cross-reference real-time data across the cameras, reducing the likelihood of false alerts and providing more accurate assessments of the driver’s attention. Furthermore, integrating multiple cameras would create smoother collaboration between DMS and OMS, extending the system’s scope to monitor passenger safety — for example, verifying seatbelt usage or alerting the driver if someone is left in the vehicle, adding an important layer of cabin security. 

This solution has great potential, but it comes with some drawbacks. Adding more cameras increases production costs due to the extra hardware and the need for advanced software to process multiple video streams. It also makes the system more intricate, requiring precise calibration to ensure seamless operation. Additionally, these extra components draw more power, which could impact electric vehicles (EVs) in particular, where efficiency is a major consideration. 

Importance of Placement for Safety and User Experience 

In essence, selecting the optimal camera placement for a driver monitoring system is not just about meeting safety standards—it's about ensuring a smooth, frustration-free user experience. While the primary goal of DMS is to keep drivers alert and safe, the way the system is configured has a direct impact on how drivers perceive and interact with it. Poorly positioned cameras can lead to inconsistent data, triggering false positives or missing key signs of distraction, which ultimately frustrates drivers and reduces their trust in the system. If a DMS generates too many unnecessary alerts or malfunctions at critical moments, drivers are more likely to disregard its warnings or even disengage the system altogether, negating its value. 

How We Can Help 

Our expertise in testing and fine-tuning DMS solutions helps automakers create systems that enhance safety while delivering a positive user experience. By carefully considering factors like driver behavior, vehicle ergonomics, and real-world conditions, we can assist in selecting and calibrating camera positions to ensure accurate monitoring without being intrusive or frustrating. Balancing technical performance with comfort and usability is key to fostering trust in the system, enabling drivers to feel supported rather than burdened. A reliable and well-integrated DMS not only improves safety but also contributes to a smoother, more enjoyable driving experience. 

"The information provided in this blog is for general informational purposes only and does not constitute legal advice. The content and materials available here may not reflect the most current legal developments or other information." 

Authors:

Rafał Kryński, Team co-lead/ ADAS/AV Hardware Engineer

Piotr Plewa, AV/ADAS Engineer

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