Watch Your Step! Watch Your Head! Watch out!

One of the most poignant stories that a student has shared with me was an experience of getting off a bus in San Diego. My Korean student was an intrepid learner and always brought me interesting expressions that he had heard during his week outside of school. One day Kim (not his real name) came for his after-school tutoring session and looked very downhearted.

"What happened?" I asked.

"I had so very embarrassed experience," he said.

Then he proceeded to describe the situation. He was standing at the front of the bus waiting to get off. The bus driver stopped and opened the door, and as he was about to step down, the female driver said, "Watch your step…." Kim hesitated, and people standing on the sidewalk waiting to board were looking at him and wondering why he didn't get off. He stood motionless and looked at the steps. The driver repeated the phrase, but Kim stood frozen, not knowing what to do next. Yet a third time, the driver repeated herself.  This time Kim looked back at her, saying, "I AM watching the step." At that point, the driver shook her head in disgust and gestured for him to get off the bus. It was at that point that it suddenly dawned on him what the meaning of the expression was.

Why had no one mentioned this important expression to him?

My husband was also witness to a more dangerous problem. While boarding a commuter flight from the tarmac, walking up a portable staircase, one passenger after another was reminded by the rlight attendant to "Watch your head."  Each passenger looked up and lowered his or her head when going through the door. However, a very tall non-native speaker (by his accent) who thanked the attendant but never lowered his head smacked his forehead right into the low door entrance. He was clearly physically stunned, and the attendant helped him recover from his embarrassment and bump to his head. It left an impression on my husband, and he wondered whether I teach this idiom. It could be very important.  

The British have a different expression from Americans and say, "Mind your step" or "Mind your head." I doubt that either idiom is comprehensible to a non-native speaker of English without a clear context and someone explaining how we use these expressions and their meanings.