Hyundai unveils Hidden B-pillar technology to improve coach door safety

HYUNDAI has introduced a Hidden B-pillar technology using 1.8GPa ultra-high-strength steel to protect passengers in coach door designs. By integrating reinforced door latches and a racing-inspired "Hidden roll cage," the system aims to secure passenger space exceeding the 18cm distance standard required for high side-impact ratings.

While Coach Door designs increase convenience for entering and exiting vehicles and maximize the sense of openness inside, the lack of a visible B-pillar—a key structural component that protects passengers during side impacts or vehicle rollovers—has been identified as a safety challenge. The "Hidden B-pillar" technology revealed by HYUNDAI does not eliminate the B-pillar, but rather integrates the door system with the vehicle body structure to ensure safety out of sight.

Door structure completed with 1.8GPa ultra-high-strength steel and upper/lower latches

The core of the Hidden B-pillar technology reported by HYUNDAI lies in a design where the door system, rather than the vehicle body, is the primary recipient of external impact forces. The interior of the door utilizes 1.8 gigapascal (GPa) class ultra-high-strength steel beams. These steel beams serve to absorb energy during an external impact while simultaneously dispersing the impact force into the robust vehicle body.

Because the reinforced door structure cannot perform safely unless it is organically combined with the vehicle body, the latch and hook systems located at the upper and lower sections of the door have also been reinforced. In the event of a rollover, the upper latch firmly secures the door to the vehicle body, while in a side collision, the lower latch and the door's lower hook, which engages with the vehicle body, handle the impact concentrated at the bottom. This structure increases the connection strength between the door and the body to secure overall structural rigidity.

'Hidden roll cage' incorporating racing technology to maximize survival space

To increase the rigidity of the vehicle body, a "Hidden roll cage" structure, which adopts the roll cage concept used in racing vehicles, has been applied. A box-shaped structure is integrated inside the main members to increase the strength of horizontal and vertical members, and the roof side area is reinforced by inserting ultra-high-strength steel tubes and high-rigidity structural foam.

These technical solutions focus on securing survival space for passengers during a collision. Typically, to receive the highest rating in a side impact test, a distance of at least 18cm must be secured between the B-pillar and the centerline of the seat. Through the Hidden B-pillar structure, HYUNDAI has designed passenger space that exceeds this standard. HYUNDAI confirmed the safety of this structure through various verification tests that reproduce actual harsh accident scenarios.

Source: original video (YouTube)