This　paper　investigates　the　proportional-integral　(PI)　boundary　feedback　control　for　the　linear　hyperbolic　systems　of　balance　laws　which　control　and　output　measures　are　located　at　the　boundaries.　We　address　the　issue　of　feedback　stabilization　by　means　of　PI　boundary　controllers.　By　constructing　a　new　weighted　Lyapunov　function,　the　sufficient　conditions　in　terms　of　matrix　inequalities　are　developed　for　the　exponential　stability　of　closed-loop　systems.　These　results　are　illustrated　by　the　linearized　Aw-Rascle-Zhang　(ARZ)　traffic　flow　model.　We　design　a　PI　boundary　controller　to　stabilize　the　oscillations　of　the　traffic　parameters　of　a　freeway　segment　and　evaluate　the　performance　with　numerical　simulations.　(C)　2018　Elsevier　B.V.　All　rights　reserved.