Since today’s well known software product lines (SPL) approaches [1] [2] [4] [5] [6] [7] [8] [9] [12] focus on one single SPL, a methodology for connection and adjustment of multiple product lines is needed. The paper will shortly survey existing processes and methods e.g. FODA [4] for product lines and show adaptations to automotive industry. The focus of the paper will be an adapted process for automotive functional development, which is based on multiple software product lines (MSPL) and particularly regards customer-supplier relationship. It will propose a general SPL interface to manage using MSPL. The interface consists of a SPL Interface Methodology which defines steps for the adjustment of two or more different SPLs as well as a data interface (SPL Interface Data) which defines a data format for the exchange between different SPL tools. The SPL adjustment is demonstrated with a case study of an imaginary advanced driver assistance system called mobilSoft Adaptive Cruise Control (MCC), which consists of three product lines, one for the whole MCC and two for the subsystems linear tracking and traverse control.