In　view　of　the　benefits　and　a　promising　prospect　of　the　emerging　connected　vehicles　(CV),　more　and　more　vehicles　will　be　equipped　with　the　in-vehicle　human-machine　interface　(HMI).　This　study　aims　to　assess　the　comprehensive　impacts　of　HMIs　on　individual　driving　performance,　traffic　safety,　and　eco-driving　behaviour　based　on　a　driving　simulator.　In　order　to　explore　how　a　driver　responds　to　warnings　when　approaching　a　tunnel,　this　study　divided　the　experimental　road　into　five　zones　according　to　warning　positions.　A　comparative　analysis　was　conducted　to　examine　the　changes　in　driving　comfort,　speeding　behaviour,　the　standard　deviation　of　speed,　time　headway　(THW),　fuel　consumption,　and　emissions.　Results　showed　that　the　HMI　could　be　beneficial　to　speed　adjustment　before　entering　a　tunnel.　Meanwhile,　HMI　may　affect　the　THW　of　vehicles.　Drivers　were　usually　more　cautious　when　the　HMI　was　on.　However,　no　significant　effects　of　the　HMI　for　driving　comfort　and　eco-driving　behaviour　can　be　observed.　It　is　expected　that　more　efficient　technology　and　different　warning　strategies　can　be　developed　to　enhance　eco-safe　driving　for　different　zones　because　they　have　different　effects.　The　findings　of　this　study　are　also　helpful　for　active　safety　management　and　for　evaluating　the　effectiveness　of　CV　systems.　©　2021　The　Authors.　IET　Intelligent　Transport　Systems　published　by　John　Wiley　&　Sons　Ltd　on　behalf　of　The　Institution　of　Engineering　and　Technology