From:
http://www.rssb.co.uk/industry-news/platform-gap-filler-trial-reduces-incidents-at-platform-train-interface

Quote:

Platform gap filler trial reduces incidents at platform/train interface

​A trial by Heathrow Express to use gap fillers has significantly reduced
the number of incidents at the platform/train interface (PTI). RSSB will
use the evidence from this trial to update standard GI/RT7106.

Heathrow Airport Limited and Heathrow Express trialled the use of gap
fillers along its platforms at Heathrow Airport, leading to a fall in the
number of incidents at the PTI from 15 to two per year. The fillers are
made from a rubbery material, which remains firm when passengers stand on
them, but flexible if it were to come into contact with rolling stock.

The gap at the PTI always poses a risk; but for passengers travelling
through Heathrow Airport, there are additional factors to consider. Many
are unfamiliar with the GB network and they generally have lots of heavy
luggage.

- End quote

The article includes a picture, but I think mine is clearer:

https://www.flickr.com/photos/reclin...6665/lightbox/