Polestar 4 Replaces Rear Window with Camera Feed

Can a Car Without a Rear Window Really Work?

In the history of automobiles, the rear window has always been considered a given—a minimum requirement for drivers to see behind them and a seemingly unchangeable aspect of car design. However, Swedish electric vehicle (EV) brand Polestar is challenging this long-held assumption.

The company’s new model, the “Polestar 4,” has completely done away with the rear window in its design. In its place, the car features a wide-angle camera mounted on the rear of the vehicle and a high-resolution display (1480 x 320 pixels) installed on the dashboard. This camera feed entirely takes over the functions traditionally served by the rearview mirror.

Why Polestar Chose to Go “Windowless”

At first glance, removing the rear window might seem like a decision that compromises safety. However, Polestar has outlined several compelling benefits to this approach.

First and foremost, the company claims that the camera feed significantly improves rear visibility in low light or rainy conditions. While human eyes struggle to see clearly in the dark, cameras equipped with infrared and high-sensitivity sensors can provide sharp images even at night. Eliminating the rear window also allows for a smoother roofline extending to the back of the vehicle, which reduces air resistance and improves the structural rigidity of the car.

Additionally, the Polestar 4 is equipped with four short-range cameras, enabling a 360-degree surround-view system. This feature provides a bird’s-eye view of the vehicle’s surroundings. As a result, the absence of a rear window paradoxically expands the driver’s field of vision, making it potentially wider than that of traditional cars.

A Growing Trend of “Mirrorless” Cars in the Auto Industry

Polestar’s innovative move is not entirely unprecedented. In fact, the automotive industry has been moving toward digitizing physical mirrors for several years.

In 2016, regulatory changes in the European Union (EU) allowed the integration of “camera-mirror systems (CMS)“—a combination of cameras and displays—in road vehicles, replacing traditional side mirrors. Mass-market models like the Lexus ES and Audi e-tron have already adopted CMS technology. The Polestar 4 pushes this trend even further by replacing the rearview mirror with a camera, making it one of the few production cars designed as a fully “mirrorless vehicle.”

In Japan, a similar regulatory change in 2016 amended the Road Traffic Act, permitting the replacement of side mirrors with cameras. However, the conversion of rearview mirrors (interior mirrors) to cameras is not yet allowed under current regulations. As a result, if the Polestar 4 is to be sold in Japan, it may need to include a traditional rearview mirror to comply with local laws.

Redefining “Visibility” Through Digital Technology

This technological shift represents more than just a replacement of components; it redefines the act of “looking behind” for drivers.

Traditional rearview mirrors allow drivers to see the rear through an interior window. However, these mirrors have limited fields of view and are often obstructed by rear-seat passengers, cargo, or narrow pillars. In contrast, camera-based systems enable customizable fields of view. By using wide-angle lenses, they can capture areas that traditional mirrors would leave as blind spots.

Additionally, digital processing of camera feeds allows for features such as brightness adjustments at night or automatic dimming to reduce glare from the headlights of trailing vehicles. These capabilities highlight the advantages of digital systems, which Polestar claims significantly enhance visibility in low-light or rainy conditions.

Challenges and Concerns: Reliability and Regulations

Naturally, this approach is not without its challenges. The main concern is the “backup plan” in case of system failure. If the camera or display malfunctions, the driver could lose all visibility of the rear. While traditional glass windows might fog up, they still provide some level of visibility. Polestar has stated that they use a highly redundant system design to address this issue, but specific details have not yet been fully disclosed.

Another potential issue is the “unfamiliarity” that drivers might experience with camera feeds. For those accustomed to using traditional rearview mirrors, it may be challenging to judge distances accurately based on a screen display. Moreover, adjusting focus when shifting one’s gaze to a display may take some getting used to.

Regulatory hurdles also remain. As mentioned earlier, many countries, including Japan, have not yet approved the use of camera-based systems as replacements for interior rearview mirrors. For Polestar to expand globally, addressing these regulations will be a significant task.

The Future of Automotive Design

The removal of the rear window in the Polestar 4 symbolizes a paradigm shift in car design. By replacing the century-old “seeing mechanisms” of glass and mirrors with digital technologies such as cameras and displays, the automotive industry is transitioning from being an extension of mechanical engineering to one of computerized innovation.

As autonomous driving technologies continue to evolve, the importance of “direct visual observation” by drivers will likely diminish further. In this sense, Polestar 4’s bold experiment could be seen as a glimpse into the future of mobility design. The day when cars without rear windows become “normal” may not be far off.

---

Q: Won’t the removal of the rear window in the Polestar 4 pose safety risks?
A: Polestar explains that the combination of high-resolution cameras and wide-angle lenses provides a broader field of view than traditional rearview mirrors. Additionally, camera-based systems are said to perform better in low-light and rainy conditions. However, more details on backup measures in case of system failure are awaited.

Q: Will the Polestar 4 be sold in Japan?
A: Under Japan’s current Road Traffic Act, the conversion of rearview mirrors into camera systems is not yet permitted. Therefore, the Polestar 4 may need to include a traditional rearview mirror to comply with Japanese regulations. Details about its launch in Japan have not been announced.

Q: Which offers better visibility: camera mirrors or traditional mirrors?
A: It depends on the situation. During bright daytime conditions, traditional mirrors are comparable. However, in low-light, rainy, or tunnel environments, camera mirrors have the advantage. They also reduce blind spots due to their wide-angle lenses. That said, individuals may need time to adjust to potential issues like image lag or difficulty in assessing depth perception on a screen.