In any program implementing the reduction of vehicle miles traveled as a part of the State’s compliance with the federal Clean Air Act the Department shall include provisions to allow, both within Maryland and among Maryland and adjoining states: The averaging of reductions in vehicle miles traveled between different worksites of the same employer; The averaging of reductions in vehicle miles traveled between worksites of different employers; The sale between worksites and employers of credits for reduced vehicle miles traveled; and The greatest degree of flexibility in implementation, giving full consideration to the geographic differences among affected areas, in order to promote the economic and environmental interests of the areas affected.