Walking down the road, a bus hit Mr. Khan. (correct the sentence)

The original sentence contains a common grammatical error known as a dangling participle or dangling modifier. A participial phrase or other introductory phrase is said to "dangle" when the noun it describes is not clearly stated in the sentence, or when it modifies a word other than the one intended.

In the sentence "Walking down the road, a bus hit Mr. Khan," the participial phrase "Walking down the road" incorrectly seems to modify "a bus." Logically, it is Mr. Khan who was walking down the road, not the bus.

To correct a dangling modifier, you can:

    
• Change the main clause so its subject is the noun that the modifier describes. (e.g., "Walking down the road, Mr. Khan was hit by a bus.")
    
• Rewrite the participial phrase as a subordinate clause with its own subject. (e.g., "While Mr. Khan was walking down the road, a bus hit him.")

The corrected sentence "Walking down the road, Mr. Khan was hit by a bus" makes it clear that Mr. Khan is the one performing the action of walking, thereby resolving the ambiguity and correcting the dangling modifier.