鉄道信号機
Railways have greater or lesser interoperability depending on conforming to standards of [[Track gauge|gauge]], [[Railway coupling|couplings]], [[brake (railway)|brakes]], [[Railway signal|signalling]], [[communications]], [[loading gauge]], [[structure gauge]], and [[Railway signalling#Operating rules|operating rules]], to mention a few parameters. For passenger rail service, different [[railway platform height]] and [[platform gap|width clearance]] standards may also cause interoperability problems.