Laura McCullough of Arlington was on her way to work one day last week when her routine ride on the subway almost turned into a tragedy.

As Laura was about to step off her train in the Foggy Bottom station, her right foot slipped into the narrow space between the train and the platform and her leg descended so far that her knee became wedged under the floor of the subway car.

"For a few terrifying seconds," Laura recalls, "I was completely helpless with the overwhelming fear that as the train moved out of the station it would shred my leg.

"But almost immediately after I fell, a very nice gentleman who had been standing inside the train rushed over and helped me force my knee out of the wedge and back to safety inside the train.

"Unfortunately, I did not get the man's name, but I truly want to thank him, not only for his help in freeing my leg but for his reassuring attitude, which was the only thing that kept me from hysterics.

"I was quite shaken by the fall, but fortunately escaped with only scrapes and bruises to my leg and thigh."

Now that it's all over, Laura feels duty bound to offer a word of advice to subway riders. She says:

"Be extremely careful when stepping on or off a train. Even though the space between the train and the plantform doesn't look big enough for your foot, much less your leg, believe me: It is."

That's sound advice, I'd say. The transportation industry has for decades been warning, "Watch Your Step," but sometimes that sage counsel goes in one ear and out the other. Perhaps we have become so accustomed to a safe ride on public transportation that we need to be shaken up a bit.

The thought of having a leg caught between a platform and a moving train ought to shake anybody out of his complacency.