If you are looking for more information on the types of signals used by MAX light rail trains in Portland & surrounding areas, this is your starting point.
Discussion about signals has spanned several posts because MAX uses several types of signaling systems, so here’s a consolidated index of links to help you find what you are looking for.
ABS Signals (Automatic Block Signal System)
ABS Signals Part 1: An introduction to blocks, signals, aspects, and indications.
ABS Signals Part 2: Builds on the information from Part 1, explains route indications
ABS Signals Part 3: How the signals are numbered, map of ABS territories
Pre-empt Signals: Overview, explanation of pre-empt aspects and indications, map of pre-empt territories
Standard Operating Procedures to proceed when a permissive aspect is not displayed
ABS/Pre-Empt Combination Signals
ABS/Pre-empt Combination Signals: Overview, explanation of route indications, locations of where some of these signals are used.
Dwarf Signals and C-Signals: Dwarf signals protect mainline power switches when trains are running reverse traffic in ABS territory. The C-signal sort of functions as a relay to let operators know their call went through at Skidmore Fountain westbound, since the pre-empt is not visible from the platform.