Child Presence Detection (CPD)

Child Presence Detection (CPD)

Child Presence Detection (CPD) is an automotive safety system designed specifically to prevent fatal heatstroke or suffocation incidents caused by children being left unattended inside vehicles. Utilising various sensing technologies, the system continuously monitors the rear passenger area for any remaining living occupants once the vehicle is switched off and locked. Upon detecting a child, it instantly triggers audible and visual alarms and alerts the owner via a smartphone app, while certain models can also automatically activate the air conditioning to regulate cabin temperature. Driven by tightening global regulations and growing public safety awareness, CPD is swiftly transitioning from a premium differentiator to a standard safety feature in new vehicles.

Tragic Background and Technical Necessity

Fatalities resulting from children inadvertently left behind in cars represent a critical global safety issue. Studies indicate that when a car is parked under direct sunlight, its cabin temperature can surge to 65°C in just 10 minutes. With children's thermoregulatory systems not yet fully matured, a mere 20 minutes in such extreme heat can cause irreversible brain and kidney damage, whilst 30 minutes can lead to unconsciousness or death. Between 2013 and 2018, China recorded 141 incidents of children trapped inside vehicles. In the United States, data from the National Safety Council reveals that nearly 40 children die from vehicular heatstroke each year. These alarming figures have directly spurred the development and mandatory regulatory adoption of CPD technology.

Core Technical Approaches

CPD detection technologies are fundamentally categorised into two main streams based on their operating principles: indirect sensing and direct sensing. Indirect sensing relies on logic-based inferences derived from door open/close logs, rear-seat pressure sensors, or child seat communication modules. Although cost-effective, this approach carries a risk of false alarms—heavy luggage on the seat could be misidentified as a child, while a motionless sleeping infant might be overlooked entirely. Direct sensing, by contrast, identifies living occupants by actively detecting heartbeats, respiration, or other vital signs, making it the prevailing mainstream solution across the industry today.

Among direct sensing solutions, Ultra-Wideband (UWB) radar has emerged as the leading technical benchmark. By transmitting pulsed signals and analysing micro-Doppler reflections caused by subtle human breathing, UWB radar precisely tracks the chest movements of infants. Its key strengths lie in three areas: first, a positioning accuracy of within ±10 cm enables it to reliably distinguish living occupants from inanimate objects such as soft toys and clothing, significantly curbing false alarms; second, its robust anti-interference capability ensures signal penetration through vehicle metal structures and seat upholstery, maintaining reliable detection even if a child is concealed beneath a blanket or positioned in the footwell; third, it can leverage the vehicle's existing UWB digital key hardware, eliminating the need for extra component costs.

Beyond UWB, millimetre-wave (mmWave) radar is another widely adopted pathway for CPD systems. Academic research has demonstrated FMCW radar-based child presence detection systems that extract range and Doppler signatures from raw radar data and deploy deep learning models to classify child age groups, achieving an impressive test accuracy of 97.43%. Furthermore, a 1DCNN-based UWB detection algorithm has achieved a 99.9% accuracy rate on low-compute MCUs while requiring less than 30 KB of memory.

Regulatory Standards and Industry Adoption

CPD systems are rapidly shifting from voluntary additions by carmakers to mandatory regulatory standards. The European New Car Assessment Programme (Euro NCAP) has incorporated child presence detection into its safety scoring protocol, compelling automakers to expedite mass deployment. Meanwhile, the UN World Forum for Harmonization of Vehicle Regulations is drafting a Global Technical Regulation (GTR) for in-cabin child presence detection, with Geely Auto contributing to the standard-setting process as an industry representative—showcasing Chinese carmakers' technical maturity in this domain.

The China New Car Assessment Program (C-NCAP) 2024 protocol has introduced CPD assessments for the first time, marking the feature's inaugural evaluation in the domestic automotive safety arena. C-NCAP stipulates that the CPD system must be capable of detecting or inferring the presence of children aged six and below, with sensing coverage spanning at least the second row of seats. The alarm must trigger within 10 seconds of vehicle locking and must emit distinct external acoustic and visual signals to differentiate from standard vehicle-locking feedback chimes. While C-NCAP currently accepts both indirect and direct sensing methods, future iterations are set to prioritise direct sensing solutions offering higher precision and lower false alarm rates.

Current Market Adoption

Several carmakers have already rolled out CPD into commercial series production. The ZEEKR 9X features a UWB-based CPD setup with dual UWB chips covering both front and rear rows for blind-spot-free cabin monitoring; activating automatically upon locking, it initiates vehicle horn blasts and smartphone app push notifications if an unattended child is detected. Euro NCAP assessment results highlight that the ZEEKR X and ZEEKR 001 were among the world's first vehicles to score points for direct child presence detection. Continental has also embedded CPD capability into its CoSmA digital key platform, using the radar mode of UWB transceivers to detect occupants without requiring dedicated hardware add-ons. To date, more than 40 models across Geely's portfolio have earned coveted five-star ratings from authoritative bodies including Euro NCAP and C-NCAP.