  Modern automobiles can be considered as a collection of many subsystems
working with each other to realize safe transportation of the occupants.
Innovative technologies that make transportation easier are increasingly
incorporated into the automobile in the form of functionalities. These new
functionalities in turn increase the complexity of the system framework present
and traceability is lost or becomes very tricky in the process. This hugely
impacts the development phase of an automobile, in which, the safety and
reliability of the automobile design should be ensured. Hence, there is a need
to ensure operational safety of the vehicles while adding new functionalities
to the vehicle. To address this issue, functional models of such systems are
created and analysed. The main purpose of developing a functional model is to
improve the traceability and reusability of a system which reduces development
time and cost. Operational safety of the system is ensured by analysing the
system with respect to random and systematic failures and including safety
mechanism to prevent such failures. This paper discusses the development and
validation of a functional model of a conventional cruise control system in a
passenger vehicle based on the ISO 26262 Road Vehicles - Functional Safety
standard. A methodology for creating functional architectures and an
architecture of a cruise control system developed using the methodology are
presented.
