年長者在道路穿越的危險往往來自其較慢的行走速度、感認能力的退化， 以至於容易接受過小的間距。本研究嘗試以受試者的動作想像能力作為反映其 感認能力退化的指標，探討年長行人在道路穿越時的安全問題。本研究招募82 名受試者，其中包含42 名年長者 (60 (含) 歲以上) 與40 名年輕人 (20~45 歲)， 於實驗室中架設模擬環境測試其行走時間、動作想像與車輛到達時間估計能力、 道路穿越決策行為及安全性。實驗結果發現年長者無論是體能、動作想像能力 或者對車輛到達時間預估能力都比年輕人差，導致容易需要更長的決策時間並 接受更小的間距，以至於決策安全性較低。雖然年長者對客觀時間提示的信任 程度稍差，但客觀時間提示仍能有效提高其穿越道路決策的安全性。

Due to their poor fitness, cognition and perception, elderly pedestrians tend to misjudge gaps and accept relatively small ones. This study investigates how Motor Imagery (MI) affects street-crossing safety. We recruited 82 participants, including 42 elderly (60 or above) and 40 young (20 to 45) participants; their walking time, MI, time-to-arrival estimation (TTA) ability, and gap acceptance with the safety margin and proportion of safe crossing were examined. Objective countdown for time-toarrival of oncoming vehicles was also included to examine its effect on gap-selection behaviors. The analysis results showed that the elderly participants made more unsafe choices than the young ones did, due to their longer walking time, worse ability of MI and TTA, acceptance to small gaps and long decision time. This study also confirmed the benefit of providing objective countdown information for pedestrians in making safer street-crossing decisions. This study suggests that MI training may benefit streetcrossing safety. Objective countdown information of oncoming vehicles may also be considered in the future to improve street-crossing safety.