Recommended Practice

Securing Control and Communications Systems in Rail Transit Environments
Part IIIb: Protecting the Operationally Critical Security Zone


This document covers recommended practices for securing control and communications security  systems in the Operationally Critical Security Zone (OCSZ) in rail transit environments.

Document History
Document Number Version Publication Date Publication Related Information
APTA SS-CCS-RP-004-16 10/26/2016 Published Current


operationally critical security zone (OCSZ), control and communications security, cybersecurity,Demilitarized Zone (DMZ), rail transit vehicle, SCADA (supervisory control and data acquisition), wireless communication, Virtual private network (VPN), incident response, secure coding


This document provides control and communications security systems designed to protect a transit agency’s OCSZ, including traction power and non-life-safety critical SCADA systems. Systems in this zone must be protected from cyber-risks to ensure proper functioning of the transit system.

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