The　tunnel　sidewall　is　important　in　ensuring　safety　and　efficiency.　This　study　investigated　the　influence　of　the　complexity　of　the　tunnel　sidewall　pattern　elements　on　driving　behavior　through　driving　simulator　experiments.　Three　kinds　of　sidewall　patterns　with　different　complexity　(sports　icon;　sports　icon　and　ribbon;　sports　icon,　ribbon　and　snowflake)　was　designed　and　compared　with　the　tunnel　without　sidewall　pattern,　and　27　drivers　participated　in　the　experiments.　Meanwhile,　the　speed,　the　standard　deviation　(SD)　of　speed,　acceleration,　the　SD　of　acceleration,　lateral　position,　accelerator　power,　and　steering　wheel　angle　were　used　as　indicators　to　explore　the　significance　and　effect　size　of　each　indicator　by　one-way　repeated-measures　ANOVA.　Thus,　the　influence　of　sidewall　patterns　with　different　element　complexity　on　driver　behavior　is　obtained.　The　results　show　that　a　reasonable　design　of　the　tunnel　sidewall　is　beneficial　to　traffic　safety　in　the　tunnel　and　provides　a　theoretical　basis　for　the　design　of　the　tunnel　sidewall　pattern.　©　2021　CICTP　2021:　Advanced　Transportation,　Enhanced　Connection　-　Proceedings　of　the　21st　COTA　International　Conference　of　Transportation　Professionals.　All　rights　reserved.