The automatic block systems uses signals (home, departure and block signals) to automatically display stop signals using track circuits installed in block protection areas when trains or cars are present in block sections or overlapping sections.
There are a number of types of automatic block systems, allowing a suitable system to be selected in line with the traffic demand over the railway division in question.
a. Block systems for double track sections
Double-track sections are divided into inbound and outbound tracks with trains constantly operated in the same direction over a single track. Therefore, blocking applies only to continuing trains. In Japan, Ministerial ordinance stipulates that the three position signal (red, yellow and green) type automatic block system be used on all double-track sections other than ATC sections.
Figure 5 shows an example of the automatic block system for a double track section.
Here, the tracks inside and between the stations are divided into a number of block sections in accordance with the train operation plan, and home, departure or block signals which are automatically controlled by track circuits are installed at the leading edge of these sections. This block system integrates blocking with signaling, and signal usage is as follows.
Home signals : These display signals for trains entering stations
Departure signals : These display signals for trains departing from stations
Block signals : These display signals for trains entering block sections
Train stop markers: These indicate the stopping limit when departure signals are not erected at the prescribed position.
Stations without turnouts are intermediate stations where operation handling is not performed, and home and departure signals are not normally installed in these stations.
