I have recently been handed a leaflet at St John's Wood London Underground Station summarizing an interesting epidemiological investigation apparently made by the staff there of 39 escalator incidents within a year :
1. Nearly all the incidents occurred on the up escalator
2. Most of the accidents have occurred at off-peak times
3. A lot of these incidents are due to loss of balance
4. Nearly half the customers were over the age of 65y.
Not mentioned, but possibly relevant, is that SJW is a very windy station.
Can we please have a scientific explanation for this odd situation?
PS I recently fell on a down escalator, but that was because I put my hand on the stationary side panel!
You pose a very intriguing question, and one definitely outside my area of expertise. But looking into the literature, it is apparent that a breadth of data exists examining accidents on escalators. It appears in general elderly individuals are the primary demographic that become injured on escalators, and most injuries are due to falls on the escalator (as opposed to falling over the railing due to improper use or horseplay). Additionally, a major factor in many cases is the use of drugs or alcohol, which may not be reported in your SJW situation.
My conclusion is that the cause is multifactorial. First, the fact that elderly individuals are involved is highly indicative of a perception imbalance that occurs when the appropriate timing is necessary to step from the moving stairs to the immobile platform. This may be easier on the down escalator as the transition is more gradual and may be observed for the entire ride on the escalator (as opposed to the up escalator where you must adapt quickly as you come over the top). Additionally, there may be the factor of attentiveness. You state that the majority of incidents occurred during off hours. This could potentially lead an individual to pay less attention to the escalator and lead to an incident (whereas if the escalator is crowded, there is more attention spent on the people in front and behind you, which may also give a person a guideline on when/where to step during exiting of the escalator). Last, adding the complication of wind may also alter balance and concentration if persons on the escalator are paying attention to their personal belongings blowing in the wind as opposed to watching their step.
Together, this is all conjecture but may give you a different insight into your question.
~Adam
In case the other person did not cover it, you should know that as you age, your base of support shrinks, especially behind you. That may be a factor -- less ability to compensate rapidly for backward perturbation.
Another thought: if head is titled back more when getting on, that could affect things. People are less stable w/ head back than head upright. However, the amount of head tilt when getting on may not be enough to matter (?).
Another factor may be the visual situation: much better optical flow from ground stimuli stepping off, I would think, than getting on, as you look up more towards a visual stimulus that is moving when getting on, whereas you have a better view of a stationary world below you when getting off. Just a conjecture on that last one.
Of the three guesses above, I would put my money on the shrinking base of support behind, which also has the most readily-available lit.
My money is on visual-vestibular conflict, as with sea-sickness.
Coming down, you can visually fixate on the stable distant scene.
Going up, at busy times you can fixate on the backs of the people in front. When there are few people around, the movement of the steps up the stationary side panels is visually confusing, there are few distant visual fixation reference points, resulting in unstable frames of reference and hence imbalance.
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