I don't know how long this has been around, but I'd not seen it befo

"Walking can be a quick and easy way to get around, particularly when
travelling during the busiest times, which are 08:00-09:00 and 17:30-18:30
Monday to Friday. The table below shows some popular journeys within zones
1 and 2 that are quicker to walk."

http://content.tfl.gov.uk/walking-tu...rney-times.pdf