This part ISO21069 specifies a roller brake test for determining the braking efficiency of road vehicles having a maximum authorized total mass (Code ISO-MO8) as defined in ISO1176 of more than 3,5t, being of categories M2, M3, N2, N3, O3 and O4as defined in UNECE R.E.3 and equipped with full power air (pneumatic) braking systems. Also applicable to electronic braking systems (EBS), its purpose is to ensure comparable measurement results from different testers, leading to reliable assessment of the efficiency of service braking systems wherever roller brake tests are performed.