Gridlock Mitigation and Commuter Flexibility Act of 2000 - Amends the Clean Air Act to require States, in order to reduce weekly employment-related automobile miles traveled by persons employed in moderate carbon monoxide nonattainment areas, to submit revisions to applicable implementation plans that include a provision insuring that no State or local provision of law, regulation, or ordinance has the effect of prohibiting or restricting employers in such areas from offering employees the opportunity to work on flexible weekly schedules. Defines "flexible weekly schedules" as schedules that reduce the number of work days employees are required to travel to and from the workplace during the week without reducing the number of hours of work or modifying employee compensation.