The 02 series of amendments to UN Regulation No 13-H introduces the first comprehensive set of safety requirements for electrically transmitted braking systems
April 13th, 2026 – The Official Journal of the EU has published the consolidated text of UN Regulation No 13-H, the new international standard that aims to govern braking systems in passenger cars and light commercial vehicles (categories M1 and N1 in EU classification. This publication will consolidate all amendments up to the 02 series, which entered into force on 12 June 2025, and represents the most significant update to the regulation in years given the growing prevalence of electric vehicles (EV) and advanced driver assistance systems on European roads.
The new UN Regulation contains the type-approval standard that every new passenger car placed on the EU market must satisfy in respect of its braking system. It sets out what braking equipment vehicles must have, how it must behave under normal and emergency conditions, and what happens when parts of the system fails. It also governs how the driver should be warned of faults, and what performance benchmarks brakes must meet in standarised tests. These guidelines will therefore determine whether a car’s brakes are legally fit for commercialisation in Europe. They will apply to all passenger cars and light vans, with the notable exception of vehicles for disabled drivers, and those with a top speed below 25 km/h. It does not cover the approval of stability and brake assist systems either, which are handled separately.
So what is new?
Conventional braking systems work hydraulically: when you press the pedal, fluid pressure travels through pipes and physically clamps brake pads against discs. The 02 series introduces a new regulatory category, the Electrical Transmission Braking System (ETBS), for vehicles where that hydraulic connection is replaced entirely by electrical signals and electrically actuated components. This so-called brake-by-wire technology is already found in a number of current electric vehicles and is expected to become significantly more common as EV architectures evolve. Until now, the regulation had not comprehensively addressed what happens when the “fluid” in a braking system is replaced by battery charge.
The new framework treats the electrical storage devices powering the brake system similarly to how hydraulic accumulators were treated before: they must be capable of delivering a defined level of braking performance after eight full brake applications, and must still achieve at least secondary braking performance on the ninth. The regulation also requires that, on the very first application after the vehicle is started, full service braking performance must be achievable, not just emergency levels.
One of the more novel aspects of the ETBS framework is its treatment of battery degradation. Unlike hydraulic fluid, electrical storage devices degrade over time, and their ability to power a braking system diminishes with age. The regulation now requires manufacturers to fit an indicator showing the driver the ageing state of the braking battery, with at least four visible levels before a maintenance warning is triggered. It also mandates a continuous Energy Management System that monitors the battery’s actual ability to perform, not just its charge level, and activates warning signals when performance falls below required thresholds. Manufacturers must document and demonstrate to type-approval authorities how this system works and how it remains accurate across different temperatures and operating conditions.
The regulation has introduced a specific Low Energy Emergency Function for ETBS vehicles: If the braking battery reaches a critically low state and an acoustic warning has been active for 60 seconds, the vehicle must automatically and progressively reduce its speed so that it cannot exceed 20 km/h. Once stopped, the vehicle must be prevented from rolling away and must retain enough power to apply the parking brake. This is a fail-safe of last resort, designed to ensure that a driver is never left without meaningful braking capability even in a worst-case battery failure scenario.
The regulation tightens and expands the warning signal framework for all electronically controlled braking systems, not just ETBS. A red warning signal must be activated whenever the service braking system can no longer achieve prescribed performance or when at least two independent braking circuits cannot each meet secondary braking requirements. A yellow warning signal covers lower-severity electrically detected defects. For ETBS specifically, an acoustic warning must also follow the red signal within 60 seconds, and a failure of the Energy Management System itself must trigger both a visual and acoustic alert.
The 02 series also formalises requirements for vehicles equipped with Automated Driving Systems (ADS). Where an ADS controls braking, the transmission links between the ADS and the braking equipment are subject to the same electronic safety analysis requirements as the rest of the system. Detected braking faults must be transmitted to the ADS while it is active, and compliance with braking performance requirements during autonomous operation must be demonstrated.
The core framework for conventional hydraulic braking systems remains largely intact. Performance benchmarks for service, secondary, and parking braking, including stopping distance and deceleration requirements, are carried over from previous versions. The anti-lock braking system (ABS) provisions, the brake force distribution requirements between axles, and the Type-0 and Type-I performance tests are all retained.
