A method and system for design and modeling of transmission lines are provided. The method includes providing a set of models of core structures (211) of transmission line cells and expanding each of the models of core structures (211) to include different neighboring elements. The parameter characteristics of the expanded core structures (214a-214c) are compared to determine a model having a minimal sufficiently closed neighborhood environment. A closed neighborhood environment complies with design rules to ensure desired transmission line behavior in a real design environment. A model having a closed neighborhood environment can be used as a stand-alone model of the core structure describing the transmission line behavior in the actual design environment.