Section 509-K. Ill or fatigued operator

No driver shall operate a bus and a
  motor  carrier  shall  not  permit  a  driver to operate a bus while the
  driver's ability or alertness is so impaired, or  so  likely  to  become
  impaired,  through  fatigue,  illness  or any other cause, as to make it
  unsafe for him to begin or continue to operate the bus. At  the  request
  of the driver or the motor carrier such illness, fatigue, or other cause
  shall  be  certified  by  a qualified physician.   However, in a case of
  grave emergency where the hazard to occupants of the bus or other  users
  of  the  highway would be increased by compliance with this section, the
  driver may continue to operate the bus to the  nearest  place  at  which
  that hazard is removed.