ITE Western District 2012 Annual Meeting

Applications of High-Resolution Traffic Event Data: Managing Oversaturated Arterials

Dr. Xinkai Wu, Assistant Professor

Department of Civil EngineeringCalifornia State Polytechnic University Pomona

ITE Western District 2012 Annual Meeting

High-Resolution Event Data

08:09:15.012, D8 on, 7.902s 08:09:15.481, D8 off, 0.468s 08:09:16.761, G3 off, 29.389s 08:09:16.761, Y3 on, 179.021s 08:09:17.620, D9 on, 2.686s 08:09:18.151, D10 on, 2.593s 08:09:18.307, D9 off, 0.687s 08:09:18.823, D10 off, 0.671s 08:09:20.244, Y3 off, 3.482s 08:09:21.649, D22 on, 80.953s 08:09:22.008, D22 off, 0.359s 08:09:23.242, G1 on, 172.806s

D e te c to r # 8 o n a t 0 8 :0 9 :1 5 .0 1 2 ;V a c a nt tim e is 7 .9 0 2 s

G re e n P ha s e # 3 o ff a t 0 8 :0 9 :1 6 .7 6 1 ;G re e n d u ra tio n tim e is 2 9 .3 8 9 s

D e te c to r # 9 o ff a t 0 8 :0 9 :1 8 .3 0 7 ;O c c u p y tim e is 0 .6 8 7 s

Y e llo w P ha s e # 3 o ff a t 0 8 :0 9 :2 0 .2 4 4 ;Y e llo w d u ra tio n tim e is 3 .4 8 2 s

G re e n P ha s e # 1 o n a t 0 8 :0 9 :2 3 .2 4 2 ;R e d d u ra tio n tim e is 1 7 2 .8 0 6 s

ITE Western District 2012 Annual Meeting

SMART-SIGNAL Terminal Box

DAC

ITE Western District 2012 Annual Meeting

Trunk Highway 55 and Boone Ave (Golden Valley, MN)

Oversaturation

• Gazis (1963): An oversaturated intersection is defined as one in which the demand exceeds the capacity.

• Little research has been conducted on the identification and quantification of oversaturated conditions– Mostly qualitative and incomplete

1 2

1 21 ( )q q L

s s C

Detrimental Effects

• Temporally, characterized by a residual queue at the end of cycle. – Residual vehicles cannot be discharged due to insufficient

green splits– Creating detrimental effects on the following cycle by

occupying a portion of green time.

• Spatially, characterized by a spill-over from a downstream intersection. – Vehicles cannot be discharged even in green phase due to

spill-over – Creating detrimental effects by reducing useable green

time for upstream movements

Oversaturation Severity Index (OSI)

• OSI: the ratio between unusable green time and total available green time in a cycle.

• Further differentiate OSI into T-OSI and S-OSI. – Temporal dimension (T-OSI) • The “unusable” green: because of the residual queue from

the last cycle

– Spatial dimension (S-OSI)• The “unusable” green: because of the downstream

blockage

Measure T-OSI & S-OSI

• T-OSI: – Estimate the length of residual queue at the end

of cycle

• S-OSI: – Identify spillover – Calculate the reduction of green time of upstream

intersections

ITE Western District 2012 Annual Meeting

T-OSI & S-OSI Measure Using High-Resolution Traffic Event Data

Queue Length Estimation• Instead of traditional input-output approach,

we estimate queue length by taking advantage of queue discharge process

• Based on LWR shockwave theory

Queue Length Estimation• Utilize the data collected by advance detector• Identify Critical Points: A, B, C

D is ta nc e

T im e

1v

2v

ngT

nrT

nTmax1n

gT

3v

nTmin

5v

1nrT

4v

A B CLo o pD e te c to r

H

AT BT CT

dL

nLmax

D

nLmin

Break Point Identification from High-Resolution Detector Data

Case 1 - Long Queue

0

10

20

30

40

50

7:26:07 7:26:50 7:27:33 7:28:16 7:29:00

Case 1 - Long Queue

0

2. 5

5

7. 5

10

7:26:07 7:26:50 7:27:33 7:28:16 7:29:00

D etecto r O ccu p a tio n T im e

B rea k P o in t A B rea k P o in t B

T im e G a p B etw een C o n secu tiv e V eh icles

),( mm kq

),( na

na kq

P attern I : C ap acity con d ition

P attern II : F ree flow arr iv al

B reak P oin t C

(Se c )

(Se c )

T im e

T im e

(a)

(b )

ITE Western District 2012 Annual Meeting

Field Tests• Test Site: TH55 (6

intersections)• Independently evaluated

by Alliant Engineering, Inc.– At Rhode Island Ave.– Three morning peaks

(7:00am-9:00am) • Jul. 23rd, 2008• Occ. 29th, 2008• Dec. 10th, 2008

0

250

500

750

1000

6:57:36 7:26:24 7:55:12 8:24:00 8:52:48

0

250

500

750

1000

6:57:36 7:26:24 7:55:12 8:24:00 8:52:48

0

250

500

750

1000

6:57:36 7:26:24 7:55:12 8:24:00 8:52:48

M a x im u m Q u e u e L e n g th C o m p a ris o n - J u l. 2 3 rd , 2 0 0 8

M a x im u m Q u e u e L e n g th C o m p a ris o n - O c c . 2 9 th , 2 0 0 8

M a x im u m Q u e u e L e n g th C o m p a ris o n - D e c . 1 0 th , 2 0 0 8

D is ta nc e (ft)

D is ta nc e (ft)

D is ta nc e (ft)

T im e

T im e

T im e

O bs e r vat i o n

E s t i m at i o n

O bs e r vat i o n

E s t i m at i o n

O bs e r vat i o n

E s t i m at i o n

T H 5 5

A d v a n ced d etecto rs

a )

b ) R h o d e Isla n d A v e.

G len w o o d A v e.

T H 5 5

S to p b a r d etecto rs

W in n etka A v e .B o o n e A v e .

A d d itio n a l d etecto rs

P h a se 6

P h a se 24 0 0 ft

2 6 3 5 ft 8 4 2 ft 1 7 7 7 ft

3 7 5 ft

SOSI: Identify Queue-over-detector (QOD) Caused by Spillover

Q O D ca u sed b yred in terv a l

D istanc e

T im e

A SC

QODST

OCCSt

QODET

4v2v

Q O D ca u sed b ysp illo v er

S to p -b a r d etecto r

A d v a n ce d etecto r

ngT

nrT

1ngT

OCCEt

E

D o wn str e am

U p str e am

ITE Western District 2012 Annual Meeting

S-OSI: Identification of Spillover

• Identify QOD-II.• High-resolution data.

Occupati on Ti me

6800

7000

7200

7400

7600

7800

17: 12: 20 17: 13: 03 17: 13: 47 17: 14: 30 17: 15: 13

D etector O ccu p an cy T im e for W es tb ou n d T H 5 5 at R h od e Is lan d A v e.D i s tanc e ( fe e t )

Ti m e

O c c upanc y Ti m e o f Advanc e D e te c to r

O c c upanc y Ti m e o f Sto p-bar D e te c to r

2v2vQ O D c a u s e d b y re d p h a s e Q O D c a u s e d b y s p illo v e r

S top -b arD etector

A d v an ceD etector

ITE Western District 2012 Annual Meeting

Managing Oversaturation: A Simple Forward-Backward Procedure

ITE Western District 2012 Annual Meeting

A Simple Forward-Backward Procedure

• Based on TOSI and SOSI measurements• Respond and mitigate traffic congestion quickly • Simple and effective• Reactive

ITE Western District 2012 Annual Meeting

Problem Setting• N intersections along an oversaturated path• At control period t, decisions are made according to the

average TOSI and SOSI values at the control period t-1, i.e.,

1,

1,

( 1)

( 1)i

i

TOSI t

SOSI t

2,

2,

( 1)

( 1)i

i

TOSI t

SOSI t

3,

3,

( 1)

( 1)i

i

TOSI t

SOSI t

,

,

( 1)

( 1)N i

N i

TOSI t

SOSI t

I n te r s ec tio n 1 I n ter s ec tio n 2 I n te r s ec tio n 3 I n ter s ec tio n N

, ,( 1), ( 1)n i n iTOSI t SOSI t

ITE Western District 2012 Annual Meeting

Basic Mitigation Strategies• The TOSI and SOSI values can help identify

the causes of arterial traffic congestion• Positive SOSI indicates the spill-back of

downstream queue• Positive TOSI indicates that the available

green time is insufficient for queue discharge• Therefore for a single intersection, three

basic strategies can be applied.

ITE Western District 2012 Annual Meeting

TOSI > 0

D is ta n ce

Tim e

# n

# n + 1

D is ta n ce

Tim e

S h o c k w a ve Tr a j e c t o r y

.n ig

S h o c k w a ve Tr a j e c t o r y D is ta n ce

1,n ir 1,n ig

,n ir ,n ig,n iO

1,n iO 1,n ir 1,n ig

,n ir ,n ig,n iO

1,n iO

V e h i c l e Tr a j e c t o r y

fv fv

V e h i c l e Tr a j e c t o r y

• Extending green

ITE Western District 2012 Annual Meeting

SOSI > 0

• Reducing red at the downstream intersection

D is ta n ce

Tim e

S h o c k w a ve Tr a j e c t o r y

# n

D is ta n ce

Tim e

1nr 1ng

nr ng

S h o c k w a ve Tr a j e c t o r y

nO

1nO

# n + 1 1ng 1nr 1ng

nr ngnO

1nO

ITE Western District 2012 Annual Meeting

SOSI > 0

• Gating (Reducing traffic arrivals & giving green to other approaches)

D is ta n ce

Tim e

S h o c k w a ve Tr a j e c t o r y

# n

# n + 1

1nr 1ng

nr ngnO

1nO

D is ta n ce

Tim e

S h o c k w a ve Tr a j e c t o r y

1nr 1ng

nr ngnO

1nO

ng

ITE Western District 2012 Annual Meeting

Handling Spillover

D is ta n ce

Tim e

S h o c k w a ve Tr a j e c t o r y

#n

D is ta n ce

Tim e

1,n ig

S h o c k w a ve Tr a j e c t o r y

#n+11, ( )n ir t

V e h i c l e Tr a j e c t o r y

fv

V e h i c l e Tr a j e c t o r y

fv

a) S p illo v e r at in te rs e c tio n n b ) A fte r R e d E x te n s io n & D o w n s tre am R e d R e d u c tio n

, ( )n ir t, ( 1)n iS t

, 1, ,( ) ( ) ( 1), [1, 1]n i n i n ir t r t S t n N

ITE Western District 2012 Annual Meeting

Forward-Backward Procedure

• Forward Process (Seeking the available green)– Follow the flow direction to eliminate spillovers

and residual queues

– Boundary condition

, 1, 1,

, 1, , ,

( ) ( ) ( 1), 2,...,

( ) ( ) ( 1) ( 1)

F Fn i n i n i

F Fn i n i n i n i

r t r t S tn N

g t g t T t S t

1,

1, 1,

( ) 0

( ) ( )

Fi

F ai i

r t

g t g t

ITE Western District 2012 Annual Meeting

Forward-Backward Procedure

• Backward Process (Gating or metering)– Follow the opposing flow direction to check the

arc capacity

– Boundary condition

, 1, , , 1, ,( ) ( ) min ( ) ( ) ( ) ( ) ,0 , 1,...,1B B a F B Fn i n i n i n i n i n ig t g t g t g t g t r t n N

, , , ,( ) min ( ) ( ) ( ) ,0B a F FN i N i N i N ig t g t g t r t

Simulation Test• 22 intersections, Pasadena, CA• Offline control

ITE Western District 2012 Annual Meeting

Simulation Test• TOSI/SOSI Changes

TOSI*Green Time

SOSI*Green Time SOSI*Green Time

TOSI*Green Time

Fair Oaks Ave SB Colorado Blvd. WB

ITE Western District 2012 Annual Meeting

Future Work• The Fundamental Diagram: Congestion

• Safety

• Environment

• Control