As　GPS　navigation　systems　become　more　powerful,　they　offer　the　convenience　of　more　efficient　travel,　and　the　use　of　such　navigational　aids　while　driving　is　now　prevalent.　Numerous　issues　still　exist　during　actual　use,　however,　such　as　incomprehensibility　and　inaccuracy　of　voice　navigation　prompts.　The　majority　of　studies　have　focused　on　humanized　design　and　the　influence　on　driving　behavior　of　GPS　navigation　systems,　while　the　psychological　factors　underlying　drivers＇　decisions　to　use　them　have　received　little　attention.　This　study　employs　the　extended　theory　of　planned　behavior　(TPB)　to　investigate　the　psychological　factors　that　influence　drivers＇　use　of　GPS　navigation　systems,　including　the　additional　variables　of　navigation　involvement,　navigation　information　quality,　and　distraction　perception.　Independent　t-tests　revealed　that　female,　non-professional,　novice,　and　highly　educated　drivers　were　more　likely　to　use　navigation　systems.　Factors　analysis　proved　the　extended　TPB　questionnaire　to　be　valid　and　reliable.　Structural　equation　modeling　showed　that　attitude　(0.19),　subjective　norms　(0.14),　perceived　behavioral　control　(0.29),　navigation　involvement　(0.36),　and　information　quality　(0.16)　significantly　influenced　drivers＇　intentions　on　the　use　of　navigation.　However,　distraction　perception　(-0.05)　had　no　significant　influence.　These　findings　demonstrate　the　need　for　navigation　systems　which　serve　drivers　better.　For　navigation　system　manufacturers,　the　humanized　design　should　be　strengthened.　For　highway　transportation　agencies,　more　consistent　designs　for　road　signs　are　needed　to　improve　the　cooperativity　between　navigation　and　traffic　signs.