Moving Block
Moving block is a train-separation method in which the protected zone behind each train moves with it, sized in real time from the train's position and braking performance. Unlike fixed-block signaling, it lets trains follow more closely, raising line capacity. It is enabled by CBTC and ETCS Level 3.
How it works
In fixed-block signaling, the track is divided into sections and only one train may occupy a section at a time, so following distance is determined by block length. In moving block, each train continuously reports its position and a central controller grants it authority to proceed up to a safe distance behind the train ahead, recalculated every few hundred milliseconds.
Moving block requires reliable train positioning, continuous train-to-wayside communication and confirmed train integrity, which is why it is realized through CBTC in metro systems and ETCS Level 3 on mainlines.
Why it matters for security
Moving block removes the physical safety margin of fixed blocks and replaces it with data. Safe separation depends entirely on accurate, timely and authentic position reports and authorities exchanged over the network, so the integrity of that data flow is a direct safety concern.
Related solution
Securing CBTC systems without disrupting automation
How CylusOne monitors moving-block signaling traffic passively, without interfering with certified behavior.
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