Raised　pavement　markers　(RPMs)　are　among　the　common　safety　features　of　roads,　playing　an　important　role　in　preventing　and　reducing　traffic　crashes.　RPMs　are　regarded　as　an　effective　measure　for　reducing　the　high　crash　rate　and　mortality　in　freeway　tunnels　in　China.　In　this　study,　a　driving　simulator　experiment　was　conducted　to　investigate　the　safety　of　RPMs　in　a　freeway　tunnel.　Two　different　RPM　layouts　were　designed　and　compared　to　a　control　with　no　RPMs,　and　32　drivers　participated　in　the　driving　simulator　experiments.　The　speed,　relative　speed　difference,　lateral　position,　accelerator　power,　acceleration,　and　pupil　area　were　used　as　indicators　of　the　response　characteristics　of　drivers　to　RPMs,　and　the　interaction　of　tunnel　length,　tunnel　zone,　and　RPM　alternatives　was　discussed.　The　results　indicate　that　a　significant　interaction　effect　exists　between　tunnel　length,　tunnel　zone,　and　RPM　alternatives.　RPMs　could　help　reduce　driver　anxiety,　boredom,　and　fatigue　caused　by　the　dark　and　monotonous　tunnel　driving　environment,　and　improve　driver　alertness　and　consciousness　of　speed.　Also,　the　driving　risk　increases　with　increasing　tunnel　length　(1800　m　to　3500　m).