这些安全措施包括将客运流量与货运流量隔离，升级列车控制系统等。
These tiers could categorize methods of operation in conjunction with safety improvements such as separation of passenger and freight traffic and advanced train control systems.
这些安全措施包括向其它服务器备份数据和对用户密码加密。
Such security measures include backing up data to other servers and encrypting user passwords.
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