This part of IS0 4190 lays down rules relating to the planning and selection of lift installations for use in residential buildings, in order to ensure adequate service. It permits, in particular, the number of lifts and their main characteristics to be defined at the very beginning of building design. Three quality levels are specified for the lift service, based on 60 s, 80 s and 100 s intervals at the main floor, and designated as follows : - programme 60; - programme 80; - programme 100. This part of IS0 4190 is applicable to standardized lifts of class I for installation in residential buildings.