Photography & Video GRAPHICS
Infographic

How positive train control works

Positive train control uses sophisticated electronics to monitor trains and take control of them if necessary to prevent collisions, derailments and other accidents.

Before a trip, data about speed limits, the track, construction zones, locations of other trains, etc. are loaded wirelessly.

 

Data

En route, the train’s position and speed are tracked via GPS. Signal status, broken rails, curves, etc. come in from wayside devices. Using these data, the system tells the engineer when to adjust speed.

Wayside device

If the engineer doesn’t act, the system takes over, adjusts speed and, if necessary, brings the train to a stop.

Red light

Before a trip, data about speed limits, the track, construction zones, locations of other trains, etc., are loaded wirelessly.

 

Data

While en route, the train’s

position and speed are tracked via GPS. Signal status, broken rails, curves, etc., come in from wayside devices. Using this data, the system tells the

engineer when to adjust speed.

Wayside device

If the engineer doesn’t act, the system takes over, adjusts speed and, if necessary, brings the train to a stop.

Red light

Sources: Federal records and interviews with rail safety experts. Graphic is schematic.

Copyright © 2016, Los Angeles Times
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