Safe train spacing is maintained via a
moving blocklight system, referred to as MAPO, installed in the cab of each train.
[11] MAPO appears in the top center of the pilot's console and looks similar to a horizontal stop light. There are three lights—green, amber, and red—and a push-button labeled "Override". The term "MAPO" itself comes directly from
Walt Disney, who formed a new company to deal with
Disneyland's transportation system directly from the profits made by
Mary Poppins.
[49]
Each monorail beam is divided into blocks based upon pylon numbering. The currently illuminated MAPO color indicates how far ahead the leading train is currently located. A green MAPO shows that the leading train is three or more blocks ahead, amber means two blocks ahead, and red indicates that the next train is in the very next block. A block is roughly between 500 and 1000 feet (about 150 and 300 m) long, although this varies. The start of each block is called a "hold point", as pilots may need to hold their trains at that location until the train ahead moves away. Guests riding in the front cab of a monorail can identify hold points by the yellow reflective tape around a pylon's number and by two yellow reflectors attached to the top outside edges of the monorail beam at that pylon.
For safety, trains must be kept at least two blocks apart during normal operation. A red MAPO indicates that train spacing has become unsafe. When a red MAPO occurs, the train's on-board computer locks out the pilot's propulsion control and applies emergency brakes. The pilot cannot resume control of the train until either the MAPO clears or the pilot presses and holds the MAPO override button.
[11]
It is the pilot's responsibility to avoid a red MAPO during normal operation. When the MAPO switches from green to amber, this indicates that the monorail is approaching the train ahead. The pilot must stop the train before crossing into the next block of beam way and hence before the MAPO switches to red.
it’s the same story at VGF at Christmas.
