CEE410 - Part 2 Flashcards
Principle of open circuit track.
Battery and an alerting device gets coupled to the two isolated rails. When a wheelset runs on the track, the circuit closes due to current being transferred through the rails and wheelset. This sets off the alerting device.
Shunting
Wheelset completing an electrical circuit within a block
Yellow over green (NORAC)
Approach medium
Proceed approaching next signal at medium speed
Yellow/yellow over red (NORAC)
Approach
Proceed prepared to stop at next signal (reduce to medium speed if not already done)
Red over green (NORAC)
Medium clear
Proceed at medium speed until entire train clears interlocking or spring switches, then proceed at normal speed
Elements of the closed track circuit
Rails Track battery Resistors Insulated joints Track relay 2-3 V DC
Signal battery
Signal lamps
12-15 V DV
Four basic signal types in North America
Color light
Searchlight
Position light
Color position light
Permissive Signals
Intended to space trains- thereby preventing rear-end collisions
Useful for double track
Used sometimes on single track
Most restrictive indication is stop and proceed
Absolute signal
Intended to prevent collisions due to opposing or conflicting trains
Typically used at junctions, movable bridges
Most restrictive indication is stop
How to distinguish permissive and absolute signals
Permissive:
Staggered
Number plate
Absolute
Aligned
No number plate
Advanced types of signals
Doll Arms
Brackets
Dwarfs
High signals
Speed definitions
Normal, maximum authorized
Limited, 45
Medium 30
Slow 15
Restricted, visible/2
Introduction to train braking systems?
Is this needed?
Safe braking distance
Basis for design criteria when planning or building a traffic control system
Accounts for all possible variability within expected parameters of system
Conservative assumptions in all parameters
Principal elements of an Safe braking distance model
A: entry point when braking model initiated
B maximum speed C Operator seeing Hand reaction time D equipment Time E braking set up time and application F final stopping Time
S = total stopping Time
