A car that won’t crash at 60 km/h (Part 1): loosening restrictions through policy “explanation”

"Collision-avoiding cars" that automatically apply the brakes when driving at low speeds have been on the market in Japan for about a year and a half. Recently, more and more models are equipped with collision-avoiding systems, and Japanese manufacturers are also developing systems that support high speeds. How far will collision-avoiding cars evolve?

"Collision-avoiding cars" that automatically apply the brakes to avoid collisions after detecting obstacles ahead using sensors are expanding the speed range in which they can avoid collisions from low speeds to high speeds (Figure 1).

Figure 1: A system that can use automatic braking to avoid collisions even when driving at a high speed of 60 km/h An experimental car equipped with a collision avoidance system that Nissan is developing. Currently, the collision avoidance systems used by various companies only support speeds below 30 km/h, but will support higher speeds in the future.

In August 2009, Volvo of Sweden introduced a system in Japan that can avoid collisions at speeds below 15 km/h. Since then, Fuji Heavy Industries, Volkswagen of Germany and Volvo have successively launched cars that can avoid collisions at speeds of 30 km/h in 2010 and 2011. In addition, Nissan Motor announced that it is developing a system that can avoid collisions at speeds of 60 km/h (Figure 2, Table 1).

Figure 2: Collision avoidance systems continue to improve Volvo's "XC60" supports speeds below 15km/h, Fuji Heavy Industries' "Legacy" and Volkswagen's "Passat CC" support speeds below 30km/h, and Volvo's "S60" supports speeds below 35km/h (mainly pedestrians). Nissan plans to make the system that supports 60km/h reach a practical level by 2013.

What effect can the extension of the collision avoidance system to high speeds bring? Data analysis of automobile accidents shows that when the speed is 0-30 km/h, most accidents are minor injuries, while when the speed reaches 40-60 km/h, the proportion of fatal accidents increases sharply (Figure 3).

Figure 3: The proportion of fatalities and injuries at various speeds When driving at low speeds of 0 to 30 km/h, most accidents are minor injuries, and the death rate is very low. However, at high speeds of 40 to 60 km/h, the death rate increases. If cars that can avoid collisions at high speeds are put into practical use, it will help reduce fatalities. (Excerpt from ITARDA's 2009 Traffic Accident Case Investigation and Analysis Report)

This data is not only for cars, but also for pedestrians. Therefore, Fuji Heavy Industries and Volvo have adopted collision avoidance systems that are not only for cars, but also for pedestrians. If the collision avoidance system can be used at high speeds, it is possible to reduce the deaths of both car drivers and pedestrians.

Relying on policy "explain" to relax

There are three factors supporting the collision avoidance car system: relaxation of regulations (technical guidelines of the Ministry of Land, Infrastructure, Transport and Tourism of Japan), improvement of the performance of sensors and ESC (anti-skid device), and reduction of system costs (Figure 4).

Figure 4: Factors that make anti-collision cars practical The Japanese Ministry of Land, Infrastructure, Transport and Tourism’s independent regulations (technical guidelines) have been relaxed, system costs have been reduced, and sensor and ESC performance have been improved.

The technical guidelines of the Ministry of Land, Infrastructure, Transport and Tourism of Japan previously did not allow the introduction of collision avoidance systems. When sensors such as millimeter-wave radar and stereo cameras detect an obstacle in front, the brakes are only allowed to be activated by ESC within 1.4 seconds before the collision. The original system was called the collision mitigation brake, which was designed to reduce collision damage in the event of a collision (Figure 5). Recently, manufacturers have adopted a system that can avoid collisions, which is completely different.

Figure 5: Braking force according to technical guidelines (Ministry of Land, Infrastructure, Transport and Tourism of Japan) The technical guidelines themselves are the same as before the introduction of the collision avoidance system, but the interpretation has changed. The conditions of avoiding excessive reliance on the system by the driver and not interfering with driving operations can also be met after the interpretation change.

Volvo, which first introduced a collision avoidance system in Japan, equipped the XC60 with a function that can prevent a collision by applying the brakes within 1.4 seconds before a collision (within the original technical guidelines) and by preventing a collision as long as the speed is below 15 km/h. This system automatically brakes to prevent a collision, thus overturning the premise of a collision.

The anti-collision system was introduced because the Ministry of Land, Infrastructure, Transport and Tourism of Japan believed that "through various experiments, it was found that as long as the speed is below 30km/h, the driver will not over-trust the anti-collision system." In order to allow the introduction of the XC60 in Japan, the Ministry of Land, Infrastructure, Transport and Tourism of Japan added an "explanation" to the technical guidelines in May 2009 (Table 2).

The interpretation of the Ministry of Land, Infrastructure, Transport and Tourism of Japan stipulates that the use of collision avoidance systems is allowed within the scope of avoiding drivers' over-reliance on collision avoidance systems. Specifically, "the collision avoidance system must be activated at low speeds (less than 30 km/h), the distance between the vehicle and the obstacle must be within 1m when the vehicle stops, the negative acceleration before the collision must reach 0.6G or more, the brakes must be released within 3 seconds after the vehicle stops, and the time differential of the negative acceleration when avoiding a collision must reach 12m/s ³ ". Since the Ministry of Land, Infrastructure, Transport and Tourism of Japan has approved the system, domestic manufacturers have also begun to adopt it. Fuji Heavy Industries adopted a system that can avoid collisions even at speeds of 30 km/h (higher than the 15 km/h of the XC60) on the "Legacy" launched in May 2010. The system adopted by Fuji Heavy Industries complies with the interpretation added by the Ministry of Land, Infrastructure, Transport and Tourism of Japan when Volvo introduced the system. However, Fuji Heavy Industries considered a system that can avoid collisions even at speeds above 30 km/h when developing it. Through negotiations with the Ministry of Land, Infrastructure, Transport and Tourism of Japan, the explanation was changed when the Legacy was introduced, from the original use below 30km/h to use in all speed ranges. In addition to the relaxation of technical indicators, there are two other factors that make the collision avoidance system practical, namely, the reduction of system costs and the improvement of sensor and ESC performance. The collision damage reduction system "Pre-crash Safety System" used by various companies was mostly combined with ACC (front vehicle tracking function), and the price was as high as 200,000 to 300,000 yen.