Permissive Block : A block governed by the principle that a train other than a passenger train may be permitted to follow a non-passenger train in the block
Ilan Kelman (ed.), Vulnerability and Resilience Definitions and References, Version 2, 2007. http://www.islandvulnerability.org/docs/vulnres.pd f, (Vulnr and Resilience - Brit) {524}