Methodology for collision risk assessment of flow corridor concept

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Methodology for Collision Risk Assessment of Flow Corridor Concept

Yimin Zhang (PhD Student)John Shortle (PhD)Lance Sherry (PhD)

24th April, 2013

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Agenda

1. Introduction

2. Problem Statement

3. Proposed Methodology

4. Results

5. Future Work

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Demand Forecast

• FAA forecasts that the air transportation industry will grow from 731 million passengers in 2011 to 1.2 billion in the year 2030.[1]

• It is projected that en route activity will increase 2.5 percent annually, reaching 64.1 million aircraft handled in 2030. [1]

En-route delays increase by 500% with 20% increase.[2]

Controller workload is one of the factors that limits en route capacity.

3 [1] FAA aerospace forecasts fiscal years 2010 – 2030[2] FAA report, National Airspace System (NAS) En Route Airspace Assessment, 2007

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Flow Corridor ConceptNextgen Conops: 2.3.3.2 En Route and Cruise Trajectory-based Operations (TBO)

Flow corridors consist of long tubes or “bundles” of near-parallel 4DT assignments.

4 Joint Planning and Development Office, “Concept of Operations for the Next Generation Air Transportation System,” Ver. 3.2, Washington, DC, 2012.

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Objective of Flow CorridorWhat?• Achieve high

throughput with low workload

• Implement along with optimal route and be able to shift dynamically

• Meet safety requirements.

5

How?• Achieve high density

in the corridor• Unidirectional• Apply self separation

• RNAV capabilities

• Separate corridor traffic from other traffic by regulations

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Literature Review

6

.

.

.

.

.

.

Paper/CategoryConcept

descriptionGeometry

design Aircraft capabilities

and equipage

Regulation and attributes

design

Safety Analysis

Zellweger D. 2002 xAlipio, J. 2003 x x

Yousefi, A. 2004 x xSridhar, B. 2006 x x

Kopardekar, P 2007 x xMundra, A. 2007 x x xHoffman, R. 2008 x x x x

Xue, M 2008 x xWing, D. 2008 x x x x

Yousefi, A. 2009 x x xYouse x x

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Problem Statement

• What is the collision probability of flow corridor concept?

• What factors will affect the collision probability most?

7

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Agenda1. Introduction/Scope

2. Problem Statement

3. Proposed Method

4. Preliminary Results

5. Future Work

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Events Leading to Collisions • Event 1: following aircraft collides/has NMAC with leading

aircraft in corridor.

• Event 2: aircraft switching lanes collides/has NMAC with another aircraft in the destination lane.

• Event 3: two adjacent aircraft switching lanes almost at the same and collide/have NMAC in the middle of maneuvers.

9

1 2

2

1 3

2

1 3

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Proposed Method

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Dynamic event tree (DET) and fault

tree analysis

Arrival process,Aircraft parameters, Simulation

Separation parameters.Pr{event i}

Event i,Conflict detection and resolution functions,Components failure probabilities.

Pr{collision | event i}

Bojia Ye, etc., Risk-capacity Tradeoff Analysis of an En-route Corridor Model, ICRAT 2012.

i

ii }event |collisionPr{*}event Pr{)collisionPr(

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Resolution maneuvers

• Onboard Conflict Detection and Resolution (CDR) system

Autonomous Flight Management Concept

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Flight crew

FMS/Auto Pilot

Airborne Separation Assistance System

(ASAS)

All aircraft stateinformation

All flight plans

Required timeof arrival, etc.

Right-of-wayrules

Desired resolution

Weather and hazardinformation

Wing, D. et al. “Function allocation with airborne self-separation evaluated in a piloted simulation”, NASA Langley Research Center Technical Report NF1676L-9177. 2010

0(NMAC)

minutes

1

ACAS

2 5 20

Strategic Intent-based

CDR

Tacticalintent-based

CDR

Tactical state-based

CDR

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No

Dynamic Event Tree for Lane Change Event

12

No

t > TTI

NoYes

t • TTI

Conflict resolved

Aircraft 1 can detect and generate tactical intent-based resolution options in next • ?

t = t – • 1

t = T0

Pilot accepts resolution?

t = t – • 1

No

t > TTI

Yes

t < TTI

t > TTI

t < T1

Yes

t • T1

Assumptionst time to NMACT0 (5mins) time to start detection for aircraft 1T1 (4mins) time to start detection for aircraft 2TTI (2mins) time to start tactical

state-based function

2

1

To tactical state-based function

Aircraft 1 starts changing lanes and have collision oncourse with aircraft 2.

At least one aircraft can detect and generate tactical intent-based resolution options in next • ?

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No

Dynamic Event Tree for Lane Change Event (Cont)

No

t > TTI

NoYes

t • TTIConflict resolved


t = t – • 1

t = T0


At least one aircraft can detect and generate tactical state-based

resolution options in next • ?

t = t – • 1

No

t > TTS

t = t – • 2

ACAS

Assumptionst time to NMACT0 (5mins) time to start detectionTTI (2mins) time to stop TICDRTTS (1min) time to stop TSCDR

t > TTS

No

t • TTSConflict resolved


t = t – • 2


No

t > TTI

Yes

t < TTI

t < T1

Yes

t • T1

Tactical intent-based

CDR function

Tactical state-based

CDR function

ACASfunction

Locatability function

2

1

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Locatability Reliability Diagram

NAVi Navigation systems on aircraft i such as GPS etc.ADS-B_in_TRNi ADS-B_in transponder on aircraft iADS-B_out_TRNi ADS-B_out transponder on aircraft i TIS-B TIS-B radar system that broadcasts aircraft position dataTIS-B_TRNi TIS-B on board transponder on aircraft i Note : components are assumed to be independent of each other.

2

1

Wing, D.J. and Cotton, W.B., “Autonomous Flight Rules: A Concept for Self Separation in US Domestic Airspace”, NASATechnical Paper, 2011

Aircraft 1 can locate both aircraft

ADS-B_in_TRN1 ADS-B_out_TRN2 NAV1 NAV2

TIS-B ADS-B_in_TRN1

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Tactical Intent-based CDR Reliability Diagram

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FMS1 TICDR_TGEN1

ASAS_SPK1

PFD1 Aircraft 1 can generate and display tactical intent-based resolution options to pilots

FMS1 Flight management service on aircraft 1TICDR_TGEN1 Tactical intent-based CDR trajectory generator on aircraft 1ASAS_SPK1 ASAS aural system on aircraft 1PFD1 Primary flight display on aircraft 1

2

1


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Tactical State-based CDR Reliability Diagram

TSCDR_TGEN1 Tactical state-based CDR trajectory generator on aircraft 1ASAS_SPK1 ASAS aural system on aircraft 1PFD1 Primary flight display on aircraft 1

TSCDR_TGEN1ASAS_SPK1

PFD1 At least one aircraft can generate and display to pilots tactical state-based resolution options

2

1


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ACAS Reliability Diagram

ACS_TRN1 ACS_SPK1 ACS_TCS1

TCAS functional on both aircraft

ACS_TRNi TCAS transponder (mode-S datalink) on aircraft iACS_SPKi TCAS speaker on aircraft iACS_TCSi TCAS elements on aircraft i (other than speaker and transponder)

Based on: Blum, D., D. Thipphavong, T. Rentas, Y. He, X. Wang, M. Pate-Cornell. 2010. Safety analysis of the Advanced Airspace Concept using Monte Carlo simulation. AIAA Guidance, Navigation, and Control Conference.

ACS_TRN2 ACS_SPK2 ACS_TCS2

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• 26=64 combinations of states of functions.

• Where Smn is the probability of a condition in which m is the number of tactical intent-based functions in working status and nis the number of tactical state-based functions in working status in the aircraft pair (m=0,1,2 and n=0,1,2).

Collision Probability Calculation

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Loc1 TICDR1 TSCDR1 Loc2 TICDR2 TSCDR2 Smn

1 1 0 1 0 0 S101 1 0 1 1 0 S201 1 0 1 1 1 S211 1 1 0 0 0 S111 1 1 0 0 1 S111 1 1 0 1 0 S111 1 1 0 1 1 S111 1 1 1 0 0 S111 1 1 1 0 1 S121 1 1 1 1 0 S211 1 1 1 1 1 S22

9 conditions are identified

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1 1 0 1 0 0 S101 1 0 1 1 0 S201 1 0 1 1 1 S211 1 1 0 0 0 S111 1 1 0 0 1 S111 1 1 0 1 0 S111 1 1 0 1 1 S111 1 1 1 0 0 S111 1 1 1 0 1 S121 1 1 1 1 0 S211 1 1 1 1 1 S22


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p

No

No

NoYes

t • TTI

Conflict resolved


t = t – • 1


t = t – • 1

No

t > TTI

Yes

t < TTI

t > TTI

t < T1

Yes

t • T1


t = T0

Each condition (Smn) requires a separate dynamic event tree.

N


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1 1 0 1 0 0 S101 1 0 1 1 0 S201 1 0 1 1 1 S211 1 1 0 0 0 S111 1 1 0 0 1 S111 1 1 0 1 0 S111 1 1 0 1 1 S111 1 1 1 0 0 S111 1 1 1 0 1 S121 1 1 1 1 0 S211 1 1 1 1 1 S22


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2p-p2

No

No

NoYes

t • TTI

Conflict resolved


t = t – • 1


t = t – • 1

No

t > TTI

Yes

t < TTI

t > TTI

t < T1

Yes

t • T1


t = T0

Each condition (Smn) requires a separate dynamic event tree.

N


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Collision Probability Calculation(cont)

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Fault tree analysis : apply brute-force enumeration

of all components states and determinethe probability of each condition

Dynamic event tree analysis : use different transition probabilities

in the tree given a condition andcalculate collision probabilities

}event |collisionPr{ i

}condition ,event |collisionPr{*}event |condition Pr{ jiijj

CATSR }condition ,event |collisionPr{*}event |condition Pr{ jiijj

Brute-force Enumeration

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One combination of states of components

Probability of the combination

Assign probability to

condition j

Last combination?

Next combination

Yes

No Calculate probabilities for each condition


CATSR }condition ,event |collisionPr{*}event |condition Pr{ jiijj

Transition Table for DET

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Previoustime-state pair

Current time-state pair

TransitionProbabilities

. . . . . . Probabilities based on Blum et al. (2010)

300 tactical intent-based CD 300 tactical intent-based CD override 0.999999300 tactical intent-based CD 120 tactical state-based CD 0.000001300 tactical intent-based CD 60 TCAS 0300 tactical intent-based CD override 280 Resolved 0.962112887300 tactical intent-based CD override 280 tactical intent-based CD override 0.037887113280 tactical intent-based CD override 260 Resolved 0.977682493280 tactical intent-based CD override 260 tactical intent-based CD override 0.022317507260 tactical intent-based CD override 240 Resolved 0.988492843260 tactical intent-based CD override 240 tactical intent-based CD override 0.011507157240 tactical intent-based CD override 220 Resolved 0.989492843240 tactical intent-based CD override 220 tactical intent-based CD override 0.010507157


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Results

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• All possibilities are conditional on event i.

}condition ,event |collisionPr{*}event |condition Pr{ jiijj


All functions work. The probability that ASAS can not resolve the collision is very small.

ASAS system fails to work. TCAS tries to resolve collision.

Smn Pr{condition} Pr{collision|conditions} Pr{collision}

S22 9.99E-01 1.50E-23 1.50E-23S21 1.94E-04 1.48E-22 2.87E-26S20 9.40E-09 6.72E-11 6.32E-19S12 2.74E-04 2.80E-18 7.67E-22S11 7.19E-08 2.03E-15 1.46E-22S10 1.88E-08 1.66E-08 3.11E-16S02 1.94E-04 1.22E-11 2.36E-15S01 2.66E-08 6.28E-10 1.67E-17S00 1.04E-08 4.68E-05 4.87E-13sum 1.00 4.68E-05 4.87E-13

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Sensitivity Analysis

• Vary failure probability of one component at a time increased by 10

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Summary • Process

Identify events that may lead to potential collisions Apply AFM concept for onboard conflict detection and resolution Conduct fault trees to model CDR functionsConduct dynamic event trees to model CDR flow and compute collision probabilities in terms of transition probabilities

• ResultsCollision probability given lane change event satisfies current target level of safety (10-9)Sensitivity analysis shows that ADS-B in transponder has higher impact to the entire system26

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Future Work

• Difference between events in terms of dynamic event trees• The starting points of the trees

Overtaking event starts from strategic intent-based CDR function but lane change event starts from tactical intent-based CDR function.

• The conflict detection probability It varies in terms of conflict angles.

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Question?

28

Thank You !

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Backup Slides

29

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Do En Route Delays Matter?

30 Mark Hansen, Do en route delays matter? Some preliminary evidence

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Benefit of Flow Corridor

31Wing D., etc. “Analysis of a Dynamic Multi-Track Airway Concept for Air Traffic Management”, 2008

ETMS data for 02/19/2004

Above FL300106,376 flightsOne corridor

AverageMAP value

Num

ber o

f Flig

hts

Flights comparison during peak hour for 2x demand

•Part of traffic flow goes to corridor when implemented •Traffic in the corridor does not contribute to MAP in terms of self separation capabilities

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Benefit of Flow Corridor

• When10 coast-to-coast corridors are analyzed (52000nm of active corridor length), Corridors have flow rate of 25 aircraft per hour and 60% of utilization.

• Delays are reduced by 60%.

32Yousefi, Arash, Ali Zadeh, and Ali Tafazzoli, 2010, Dynamic Allocation and Benefit Assessment of NextGen Flow Corridors, Fort Worth, Texas, 10th AIAA-ATIO Conference.

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Literature Summary, Safety Models

33

models for aircraft following

procedures

Models for Transatlantic routes

Gaps: lack of conflict detection and resolution analysis

Gaps: lack of lane change procedure

Paper

Carreño, V. 2007

EUR/SAM 2010

Gunnam,A. 2012

In-trail procedure safety analysis for Transatlantic routes using error models

Collision assessment for Transatlantic routes using Reich collision model

Benefit Analysis for Transatlantic routes

Description

models for ground

transportation

PaperDaams, J. 1999

Abbott, T. 2002

Hammer,J. 2003

Safety evaluation of encounters between free-flight

Speed control law for precision terminal area in-trail self spacing

Description

Safety analysis of an approach spacing for instrument approaches application using ADS-B

PaperJula, H. 1999

Mehmood, A. 2002

Abel, E. 2006

Institute of transportation Studies in Berkeley

Evaluation of crash rates and causal factors for high risk locations on rural and urban two lane highways in Virginia

Description

Application of system dynamics in car following models

Collision avoidance analysis for lane changing and

Collision geometry during lane change

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Related Literature

• Autonomous Flight Management (AFM) is an airborne-based automated separation assurance system.

• Advanced Airspace Concept (AAC) is a ground-based automated separation assurance system.

• Conflict detection and resolution techniques and collision risk assessment methods.

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Erzberger, H.”The Automated Airspace Concept”. the Fourth USA/Europe Air Traffic Management R&D Seminar, Santa Fe, New Mexico, USA, Dec. 3-7, 2001.Wing, D. “Autonomous Flight Rules, A concept for self-separation in U.S. domestic airspace”, NASA technical report, NASA/TP-2011-217174.

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Roles and Responsibilities Flight Crew:• Adhere to the assignment of corridor controller (e.g. re-routing).• Respond to conflict resolution given by automation and following corridor flying

procedure (e.g. lane change procedure).• Coordinate with corridor controller for exception situations

Automation: • Detect conflicts and provide resolutions a certain period of time prior to actual

conflicts.• Notify corridor controllers when conflicts can not be handled or aircraft needs to

break out the corridor to avoid a collision.

Corridor Controller:• Manage corridor configuration, traffic flow on ramp/off ramp and in the corridor• Resolve conflicts that cannot be handle by automation

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Aircraft Equipage

• Eligible aircraft must have the RNP-x and RNAV capability.

• Eligible aircraft are equipped with ADS-B, CDTI system and data link communication system.

• Eligible aircraft are equipped with automated separation assurance system.

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Advanced Airspace Concept (AAC)

• AAC is a ground-based automated separation assurance system.

• Autoresolver (AR) resolves potential conflicts 3-20minutes prior to NMAC.

• Tactical Separation-Assured Flight Environment(TSAFE)resolves potential conflicts 1-3 minutes prior to NMAC.

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AR

TCAS

TSAFE

Pilot See and Avoid

20 minutes prior to conflicts

3-20mins

1-3mins

Aircraft Aircraft Aircraft Aircraft

AutoResolver TSAFE

Controller

CentralComputer

AirGround

GroundStation

GroundStation

AAC Host

Voice Comm

UnequippedAircraft

Mode-SData link

<1min

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Simple Calculation

38

2

1

6nm

2nm

300

v1=320knots

t=60*{6/sin(300)}/320=2.25mins

CATSR Based on: Blum, D., D. Thipphavong, T. Rentas, Y. He, X. Wang, M. Pate-Cornell. 2010. Safety analysis of the Advanced Airspace Concept using Monte Carlo simulation. AIAA Guidance, Navigation, and Control Conference.

TCAS overrides tactical conflict detection?

Pilots avoid NMAC?

Not > 0

t = t –

t = 0

Conflict occurs,but no NMAC

Yes

Yes

No

NMAC occurs Collision

TCAS workson both aircraft?

Yes

NMAC occurs;Collision?

No

t = 1min

Dynamic Event Tree for Lane Change Event

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Event Tree: Automation Handoff

Controller providesresolution and pilot accepts in next ?

No

t > 1 +

t = t –

To pilotmodel

Yes

t • 1

Conflict detected

Response to tactical intent-based resolution

Tactical intent-based function generates resolution?

Handoff to controller

Handoff to TCAS

YesConflict resolved

No

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Event Tree: Pilot Response

Pilot acceptsresolution in next ?

No

t > 2 +

t = t –

Conflict resolvedYes

t • 2

Conflict resolution given

Handoff to tactical state-based CDR

Response to tactical intent-based resolution

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State / Time-> 120 110 100 90 80 70 60 30 0 -1tactical intent-based CD 0 0 0 0 0 0 0 0 0 0tactical intent-based CD override 0 0 0 0 0 0 0 0 0 0tactical state-based CD 1.00E-06 0 0 0 0 0 0 0 0 0TCAS 0 0 0 0 0 0 1.00E-12 0 0 0Resolved 0 9.78E-07 2.18E-08 4.92E-10 5.60E-12 1.26E-13 4.92E-10 4.92E-10 4.92E-10 4.92E-10tactical state-based CD override 1.00E-06 2.23E-08 4.98E-10 5.73E-12 1.28E-13 1.47E-15 0 0 0 0TCAS works 0 0 0 0 0 0 9.99E-13 0 0 0NMAC 0 0 0 0 0 0 0 0 9.01E-14 9.01E-14TCAS override 0 0 0 0 0 0 9.99E-13 3.00E-13 0 0Conflict (no NMAC) 0 0 0 0 0 0 0 6.99E-13 9.09E-13 9.09E-13Collision 0 0 0 0 0 0 0 0 0 6.06E-18

DET Output

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,ij kl kl ijq q p pkl,ij = Pr{Transition from state-k time-l to state-i time-j}

• Each cell contains a formula relating existing state-time pair to potential previous state-time pairs

• The value of existing state-time pair qij refers to the transition probability for state i at time j

Shortle, et al. “Safety and Sensitivity Analysis of the Advanced Airspace Concept for NextGen”, CNS Conference, Dulles, Virginia April 24-26, 2012

. . .

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Function Conditions

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Loc1 TICDR1 TSCDR1 Loc2 TICDR2 TSCDR2 Conditions0 0 0 0 0 0 p000 0 0 0 0 1 p000 0 0 0 1 0 p000 0 0 0 1 1 p000 0 0 1 0 0 p000 0 0 1 0 1 p010 0 0 1 1 0 p100 0 0 1 1 1 p110 0 1 0 0 0 p000 0 1 0 0 1 p000 0 1 0 1 0 p000 0 1 0 1 1 p000 0 1 1 0 0 p000 0 1 1 0 1 p010 0 1 1 1 0 p100 0 1 1 1 1 p110 1 0 0 0 0 p000 1 0 0 0 1 p000 1 0 0 1 0 p000 1 0 0 1 1 p000 1 0 1 0 0 p000 1 0 1 0 1 p010 1 0 1 1 0 p100 1 0 1 1 1 p110 1 1 0 0 0 p000 1 1 0 0 1 p000 1 1 0 1 0 p000 1 1 0 1 1 p000 1 1 1 0 0 p000 1 1 1 0 1 p010 1 1 1 1 0 p10

Loc1 TICDR1 TSCDR1 Loc2 TICDR2 TSCDR2 Conditions0 1 1 1 1 1 p111 0 0 0 0 0 p001 0 0 0 0 1 p001 0 0 0 1 0 p001 0 0 0 1 1 p001 0 0 1 0 0 p001 0 0 1 0 1 p011 0 0 1 1 0 p101 0 0 1 1 1 p111 0 1 0 0 0 p011 0 1 0 0 1 p011 0 1 0 1 0 p011 0 1 0 1 1 p011 0 1 1 0 0 p011 0 1 1 0 1 p021 0 1 1 1 0 q111 0 1 1 1 1 p121 1 0 0 0 0 p101 1 0 0 0 1 p101 1 0 0 1 0 p101 1 0 0 1 1 p101 1 0 1 0 0 p101 1 0 1 0 1 q111 1 0 1 1 0 p201 1 0 1 1 1 p211 1 1 0 0 0 p111 1 1 0 0 1 p111 1 1 0 1 0 p111 1 1 0 1 1 p111 1 1 1 0 0 p111 1 1 1 0 1 p121 1 1 1 1 0 p211 1 1 1 1 1 p22

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Sensitivity Analysis

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Locatability Function Variation 1

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TIS-B TIS-B_TRN1

State C Pr{C} Pr{collision given C} Pr{collision and C}P22 0.99952 1.50E-23 1.50E-23P21 1.94E-04 1.48E-22 2.87E-26P20 9.41E-09 6.72E-11 6.32E-19P12 2.74E-04 2.80E-18 7.67E-22P11 1.62E-05 2.03E-15 3.30E-20P10 1.57E-09 1.66E-08 2.60E-17P02 1.88E-08 1.22E-11 2.29E-19P01 2.22E-09 6.28E-12 1.40E-20P00 4.75E-08 4.68E-05 2.22E-12Sum 1 4.68E-05 2.22E-12

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Locatability Function Variation 2

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TIS-B ADS-B_in_TRN1 ACS_TRN1 ACS_TRN2

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Conflict Probability Estimation

47 R.A. Paielli, H. Erzberger: “Conflict probability estimation for free flight”, Journal ofGuidance, Control, and Dynamics, Vol 20(3), 588-596, 1997

Methodology for collision risk assessment of flow corridor concept

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