This paper addresses the problem of modeling railway systems.  We use
both Mean Value Calculus and Extended Duration Calculus to specify
railway systems.  For railway line, signal system is discussed and a
simple scheduling strategy is presented, which result in safety and
liveness of railway line; For linear railway region, both running map
and feasibility conditions are described. The framework to verify
correctness of scheduling, i.e. the running map satisfies feasibility
conditions, is also presented.