Section 149. Through highway

Every  highway or portion thereof on which
  vehicular traffic is  given  preferential  right  of  way,  and  at  the
  entrances  to  which  vehicular  traffic  from  intersecting highways is
  controlled by traffic-control signals or is required by law to yield the
  right of way to vehicles on such  through  highway  in  obedience  to  a
  flashing  red  signal, a stop sign or a yield sign, when such signals or
  signs are erected as provided in this chapter.