It massively shows down alighting time, the &quot;dwell time&quot; is already a big factor in how many tube trains can be run. It&#x27;s also very confusing to passengers. For both reasons, TfL would be extremely reluctant to introduce it at a central London station.<p>And, there are building foundations and other tunnels in the way in many cases, so it wouldn&#x27;t be a temporary inconvenience.