MIT
ICAT
MIT
MIT
ICAT
International
Center
for
Air
Transportation
Impact of Operating Context on the
Use of Structure in Air Traffic
Controller Cognitive Processes
Hayley J. Davison, Jonathan M. Histon, Margret
Dora Ragnarsdottir, Laura M. Major & R. John
Hansman
Massachusetts Institute of Technology
5th FAA/Eurocontrol ATM R & D Seminar
June, 2003
MIT
ICAT
Motivation

Structure has been identified in the en route
environment as a mechanism of cognitive
simplification

Appropriate application of structure could result in a
safe increase in the capacity of the air traffic control
system, and should be considered in:
 Airspace re-design
 Design of ATC decision aids
 Design of future ATC procedures

This study investigates whether structure-based
abstractions hold across other ATC environments
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ICAT
Methodology
 Site
Visits
 TRACONs: Boston, New York, Manchester (NH)
 En Route Centers: Boston, New York, Cleveland, Montreal
 Oceanic operations: New York, Reykjavik
 Air
Traffic Data
 ETMS enhanced data-stream
 ASR-9 data for Boston airspace
 Voice
Command Analyses
 Boston TRACON final approach frequency
 Atlanta Center’s Logen sector frequency
Proposed Air Traffic Controller
Cognitive Model
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ICAT
STRUCTURE
ATC
OPERATIONAL
CONTEXT
AIR
TRAFFIC
SITUATION
COGNITIVE SPACE OF THE
AIR TRAFFIC CONTROLLER
Surveillance
Path
Information/
Display
System
SITUATION AWARENESS
LEVEL 1
LEVEL 2
Perception Comprehension Projection
Monitoring
Evaluating
Planning
STRUCTURE-BASED
ABSTRACTION
Command
Path
LEVEL 3
DECISION
PROCESSES
Voice/Output
System
WORKING
MENTAL
MODEL
PERFORMANCE
OF ACTIONS
Implementing
Adapted from Endsley 1994, Pawlak 1996, & Reynolds, et al., 2002
“CURRENT
PLAN”
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ICAT

Previously Identified StructureBased Abstractions
Standard Flows
 Aircraft classified into
standard and non-standard
classes based on
relationship to established
flow patterns.

Standard
flow
Groupings
Non-standard
aircraft
Grouping
 Common, shared property,
used to define and control
groups of aircraft
Critical
point
• E.g. non-interacting flight
levels

Critical Points
 Intersection and merge
points between flows
 Reduce problem from 4D
to 1D “time-of-arrival”
Standard
flow
Standard
aircraft
Sector
boundary
Histon, et al., 2001
MIT
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TRACON
TRACON: Example
of Standard Flows
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
TRACON standard flows emerge from facility
SOP’s
50
60
LWM
BRONC
SR
140
110/90
SCUPP
ID
50
ID
50 40
SL
140
60
F2
50
40
ID
140
F1
60
SM
140
70
WOONS
110/100
ID
80
40
60
50
110
PVD
60
FREDO
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TRACON: Impact
of Standard Flows
COGNITIVE SPACE OF THE
AIR TRAFFIC CONTROLLER
SITUATION AWARENESS
LEVEL 1
LEVEL 2
LEVEL 3
Perception Comprehension Projection
AIR
TRAFFIC
SITUATION
DECISION
PROCESSES
Monitoring
Evaluating
Planning
STRUCTURE-BASED
ABSTRACTION
WORKING
MENTAL
MODEL
“CURRENT
PLAN”
PERFORMANCE
OF ACTIONS
Implementing



Comprehension/Projection: determine future lateral/vertical position based on
membership in standard flow
Planning/Evaluation: use the standard flow as a template for flight paths
satisfying airspace & traffic flow constraints; standard flows are non-interacting
Monitoring: easily perceive if aircraft is deviating from expected lateral path;
different strategies for aircraft not in standard flow
MIT
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Altitude & airspeed groupings used in the
TRACON
300
250
Number of commands

TRACON: Examples of
Groupings
200
150
100
50
0
150
160
170
180
Airspeed (kts)
190
200
210
MIT
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TRACON: Impact of Groupings
COGNITIVE SPACE OF THE
AIR TRAFFIC CONTROLLER
SITUATION AWARENESS
LEVEL 1
LEVEL 2
LEVEL 3
Perception Comprehension Projection
AIR
TRAFFIC
SITUATION
DECISION
PROCESSES
Monitoring
Evaluating
Planning
STRUCTURE-BASED
ABSTRACTION
WORKING
MENTAL
MODEL
“CURRENT
PLAN”
PERFORMANCE
OF ACTIONS
Implementing



Comprehension/Planning: expect certain traffic flows to have certain
altitudes & airspeeds
Evaluating: separate flows by altitude to ease load of ensuring
separation
Projection: use constant airspeeds correlate distance & time linearly so
that projection is simplified
TRACON: Examples
of Critical Points
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ICAT
Critical points in
TRACON:
Distance from radar (nm)
 Ingress points
into sector
 Egress points out
of sector
 Merging points in
traffic flows
 Holding points
Rockport Sector
merge point
North

SCUPP
BRONC
Final Approach
Sector merge point
PVD
Distance from radar (nm)
West
MIT
ICAT
TRACON: Impact
of Critical Points
COGNITIVE SPACE OF THE
AIR TRAFFIC CONTROLLER
SITUATION AWARENESS
LEVEL 1
LEVEL 2
LEVEL 3
Perception Comprehension Projection
AIR
TRAFFIC
SITUATION
DECISION
PROCESSES
Monitoring
Evaluating
Planning
STRUCTURE-BASED
ABSTRACTION
WORKING
MENTAL
MODEL
“CURRENT
PLAN”
PERFORMANCE
OF ACTIONS
Implementing



Perception/Projection: focuses point to which projections made to the
recognized critical points in a sector
Monitoring: monitors critical points in sector more frequently because the
critical points are the most likely locations of conflict
Planning: plan to meet constraints by the point the aircraft reaches the
critical point
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En Route Results
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
Distinct Types
of En-route Sectors
Cruise sectors
 High or “super-high” altitude
sectors
 Most aircraft at constant
altitude

Utica Sector
40% Transitional
aircraft
60% Cruise
aircraft
Transition sectors
 Interface between en-route
sectors and the terminal
airspace
 Similar operational conditions
as en-route sectors
• Radar update rates, limitations
on available airspace
 Tasks are similar to TRACON
airspace
• Majority of aircraft in vertical
transition
• Greater use of vectoring
Logen Sector
90% Transitional aircraft
10% Cruise
aircraft
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En Route (Cruise) Examples
Standard Flows:
Preferred Routings & Jet Routes
Critical Points:
Ingress points
Egress points
Merge points
Groupings: by altitude
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En Route (Transitional) Examples
Jets
Props
Standard Flows:
SIDs & STARs
Groupings:
Aircraft type (jet vs. prop)
Cross Logen At And
Maintain 14 Thousand
Feet
89%
Cross Womak At And
Maintain 11 Thousand
Feet
Critical Points:
Lateral/Vertical
merge point
“gates”
7%
Cross 20 Miles NW of
Grier? At And Maintain
11 Thousand Feet
2%
Cross 29 DME At And
Maintain 14 Thousand
Feet
2%
Cross Pelam At And
Maintain 8 Thousand
Feet
2%
0%
20%
40%
60%
80%
100%
Percentage of Crossing Restrictions (Altitude)
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Oceanic Results
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Oceanic ATC environment
ATC Facility
CONTROLLER
Phone or electronic
comm.
COMMUNICATION
RELAY SERVICE
(e.g., ARINC or Iceland
Radio)
VHF comm.
(if available)
HF comm.
PILOT
Aircraft 1
Aircraft 2
Aircraft n
Oceanic: Example
of Standard Flows
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Track exit points
A 310 320 330
340 350 360 390 A
B 310 320 330 340 350 360 370 380 390 B
390 C
60 370 380
3
0
5
3
0
D
0 330 34 350 360 370 380 390
2
3
0
1
3
C
0
0E
0 330 34
370 380 39
D 310 32 330 340 350 360
70 380 390 F
0
E 310 32 330 340 350 360 3
0
F 310 32
W 310 320 330 340 350 360 370 380 390 W
X 310 320 330 340 350 360 370 380 390 X
Y 310 320 330 340 350 360 370 380 390 Y
Z 310 320 330 340 350 360 370 380 390 Z
Track entry points
G
G
360
0
4
3
320
Reported Workload Impact
of Standard Flows
MIT
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Reykjavik controllers reported that they are
cognitively able to handle more traffic as
structure increases
Maximum number of aircraft in a
controller’s sector

40+
40
30
20
10
Many
crossings
Two merging
flows of traffic
Single traffic
flow
Level of Structure
Traffic on
tracks
MIT
ICAT
Oceanic: Impact
of Standard Flows
COGNITIVE SPACE OF THE
AIR TRAFFIC CONTROLLER
SITUATION AWARENESS
LEVEL 1
LEVEL 2
LEVEL 3
Perception Comprehension Projection
AIR
TRAFFIC
SITUATION
DECISION
PROCESSES
Monitoring
Evaluating
Planning
STRUCTURE-BASED
ABSTRACTION
WORKING
MENTAL
MODEL
“CURRENT
PLAN”
PERFORMANCE
OF ACTIONS
Implementing

Comprehension/Projection: determine future lateral/vertical position
based on membership in standard flow
 Planning/Evaluation: use the standard flow as a template for flight
paths satisfying airspace & traffic flow constraints; standard flows are
non-interacting
MIT
ICAT
Flight strips are grouped by
flight direction, time, & altitude
groupings reflecting grouping
strategy of controllers
23.30°N/60°S 27.28°N/55°S
E
31°N/50°S
Longitude
34.45°N/45°S
W
38°N/40°S
Altitude
Time
Altitude

Oceanic: Examples of Groupings
Longitude
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Oceanic: Impact of Groupings
COGNITIVE SPACE OF THE
AIR TRAFFIC CONTROLLER
SITUATION AWARENESS
LEVEL 1
LEVEL 2
LEVEL 3
Perception Comprehension Projection
AIR
TRAFFIC
SITUATION
DECISION
PROCESSES
Monitoring
Evaluating
Planning
STRUCTURE-BASED
ABSTRACTION
WORKING
MENTAL
MODEL
“CURRENT
PLAN”
PERFORMANCE
OF ACTIONS
Implementing

Evaluating: separates aircraft into non-interacting
altitude groupings and time groupings, which simplifies
the evaluation problem into a sequencing problem
Oceanic: Examples
of Critical Points
MIT
ICAT

Critical points:
 Ingress points
onto tracks
 Egress points
from tracks
 Position report
points
Time
A 310 320 330
340 350 360 390 A
B 310 320 330 340 350 360 370 380 390 B
0C
0 370 380 39
0 350 36
0 380 390 D
0 330 34
C 310 32 330 340 350 360 37 0 380 390 E
0
37
D 310 32 330 340 350 360
0 380 390 F
0
E 310 32 330 340 350 360 37
0
32
0
F 31
W 310 320 330 340 350 360 370 380 390 W
X 310 320 330 340 350 360 370 380 390 X
Y 310 320 330 340 350 360 370 380 390 Y
Z 310 320 330 340 350 360 370 380 390 Z
Track entry points
G
360
340
20
G3
23.30°N/60°S 27.28°N/55°S
E
31°N/50°S
Longitude
34.45°N/45°S
W
38°N/40°S
Altitude
Track exit points
MIT
ICAT
Oceanic: Impact
of Critical Points
COGNITIVE SPACE OF THE
AIR TRAFFIC CONTROLLER
SITUATION AWARENESS
LEVEL 1
LEVEL 2
LEVEL 3
Perception Comprehension Projection
AIR
TRAFFIC
SITUATION
DECISION
PROCESSES
Monitoring
Evaluating
Planning
STRUCTURE-BASED
ABSTRACTION
WORKING
MENTAL
MODEL
“CURRENT
PLAN”
PERFORMANCE
OF ACTIONS
Implementing



Perception/Projection: focuses point to which projections made to the
recognized critical points in a sector
Monitoring: monitors critical points in sector more frequently because
the critical points are the most likely locations of conflict
Planning: plan to meet constraints by the point the aircraft reaches the
critical point
MIT
ICAT
Projection Discussion
Projection identified as key ATC cognitive
task benefiting from application of structural
abstractions
 Two fundamentally different types of
projection identified in ATC: spatial-based
projection & time-based projection

 Influenced by surveillance available & procedural
restrictions
 May be aided by decision support tools (e.g.,
NASA’s TMA)
NASA’s
TMA
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Projection Discussion
Surveillance
Separation Restrictions
Spatial-based
projection
Time
23.30°N/60°S 27.28°N/55°S
E
31°N/50°S
Longitude
34.45°N/45°S
Altitude
Miles in
Trail
Time-based
projection
Mixed
projection
required
Decision
Support
Minutes in
Trail
38°N/40°S
W
Miles in
Trail
Minutes in
Trail
NASA’s TMA
MIT
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
Projection Discussion
Future surveillance advances & procedural
modifications may change the type of
projection required and/or change structure
present in the traffic
 Individualized decelerating approach procedures
are being considered in TRACON
 Time-based metering has been discovered to be
more efficient than spatial-based restrictions in the
En Route environment
 Oceanic information support may transition from a
procedural form of support (flight strip) to a spatial
form of support (situation display)

Further investigation will be conducted into
what aspects of structure provide the greatest
benefits to the projection task
MIT
ICAT
Conclusions
Evidence of 3 key abstractions found in all 3
ATC environments, details of how abstractions
apply differ
 Projection identified as key ATC cognitive task
benefiting from application of structural
abstractions
 Consideration should be given to making future
surveillance & procedures cognitively
manageable while taking advantage of existing
structure-based abstractions

MIT
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 Other
Discussion Questions
structure-based abstractions?
 Can the identified abstractions aid
cognition in other ways?