Communication networks in the railway sector are critical to the operation of the system and have stringent requirements for reliability and safety. These types of networks are commonly characterized as “mission critical.” Further, rail communication networks have requirements for interoperability with legacy technology and long life cycle support. Many of the European railways operate trackside Global System for Mobile Communications-Railway (GSM-R) wireless networks; GSM-R is based on the GSM standard with railway-specific features. The railways have started to look at Long Term Evolution (LTE) as a potential future replacement system for GSM-R. This paper presents the role of communication networks in railway operations, the resulting unique requirements for mission critical rail networks, and current trends in railway telecommunications. A brief tutorial on GSM-R is provided. We then present the LTE network architecture and assess the suitability of LTE to meet the requirements of the railway sector, with a special focus on reliability. The paper focuses primarily on mainline rail networks; however, much of what is presented also is applicable to urban rail networks. © 2011 Alcatel-Lucent.