analysis of variable speed limit system on a german autobahn

ANALYSIS OF VARIABLE SPEED LIMIT SYSTEM ON A GERMAN AUTOBAHN

Steven BoicePortland State University

M.S. Civil Engineering Candidate

A Thesis defense presented in the partial fulfillment of the requirements for the degree of

MASTER OF SCIENCEin

CIVIL ENGINEERING

July 28, 2008

ANALYSIS OF VARIABLE SPEED LIMIT SYSTEM

ON A GERMAN AUTOBAHN2

Presentation Outline

Introduction Study Area Methodology Analysis Results Outlook



Presentation Outline




IntroductionVariable Speed Limit System Speed limits that change based on real time road, traffic, and weather

conditions – Road

• Slippery pavement, visibility– Traffic

• Density, speed, truck percentages – Weather

• Rain, snow, ice, fog Speed limits, advisories, regulatory prohibitions presented to drivers via

overhead gantries– Sign centered over each lane– Enforced via radar/camera

Speed limit changes based on series of algorithms Speed limits change in order to:

– Postpone or prevent freeway breakdown– Reduce shock speeds– Increase lane homogeneity (speed/flow)– Increase safety– Increase capacity



IntroductionVariable Speed Limit System Speed limits, advisories, regulatory prohibitions presented to drivers via

overhead gantries– Sign centered over each lane



IntroductionThesis Objective

Address VSL impacts on key traffic flow parameters– Bottleneck location/reoccurrence– Bottleneck properties (shock speed, pre-queue

flow, queue discharge flow)– Lane harmonization (flow/speed)

Address by conducting empirical before/after analysis on a German Autobahn– Use real data collected from roadway sensors

along Autobahn 99 with VSL in and out of operation



Variable Speed Limit: Concept

Maintain constant flow



IntroductionThesis Motivation

VSL - Germany, United Kingdom, Netherlands, Australia– Large emphasis on safety

– Large decrease in rear end crashes

– Large decrease in speed differential

– 20-30% reduction in crash rates (Germany)

– 30% reduction in injury crashes (M25 U.K.)

– Little emphasis on impacts of traffic flow parameters

– 15% increase in shoulder lane (M25 U.K.)

– Increase in weekday traffic volumes (M25 U.K.)

– No improvement in freeway performance (A2 Netherlands)



IntroductionThesis Background

Graduate Research Assistant– Intelligent Transportation Systems Laboratory

• Empirical Analysis of German and U.S. traffic sensor data and impact on Driver Assistance Systems

o Funded by BMWo Analysis of A9

Rodger Lindgren– Analysis of A5

“Connections” allowed for access to A99 data Opportunity to compare US and German

freeways



Outline




Study AreaAutobahn 99 - Munich, Germany

A99Study Area

A99 = ¾ ring around City of Munich, Germany



Study AreaAutobahn 99 Constructed in 1930’s Total 41 kilometers (A995 to A96) ¾ ring around city of Munich Considered one of busiest roadways in Europe

– ADT = ? No ramp metering Connects roadways to City of Munich

– A96– A8– A92– A9– A94– A995



Study AreaA99 Site Facts

Parameter Autobahn 99

Northbound Southbound

Length 15.6 km 16.3 km

Cross section 2-4 lanes 2-4 lanes

Hard shoulder Yes Yes

ADT ? ?

Speed limit Passenger cars - Only when VSL active

Trucks – 80km/hr (all time)

Passenger cars - Only when VSL active

Trucks – 80km/hr (all time)

Ramps 3 off/4 on 4 off/3 on

Mainline detectors (dual loop) 13 14

Ramp detectors (dual loop) 5 6

Detector spacing 320 m – 2,917 m 505 m – 2,250 m

VSL sign gantries 10 12

VSL sign gantry spacing 1,070 m – 2,030 m 663 m – 2,250 m



Study AreaAutobahn 99

Northbound

Southbound

945125013576261280146015401075

2197 1130 1720 2030 1629 1464 1120 1130 320 750 1300

60 70 80 90 110 120 130 140 150 170 190 210 220 232

70 780 772 760 750 740 730 720 714 210 710 690

60 70 80 90 110 120 130 140 150 170 190 210

780 770 760 750 740 730 720 714 710 690

(MQ)

(AQ)

(AQ)

(MQ)

(m)

786

Legend:

dual-loop detector station variable message sign gantry hard shoulder

720

468930225016501110(m)290 37 37

3730

(hard shoulder) Lane opened in dense traffic



Study AreaAutobahn 99

Southbound

945125013576261280146015401075

60 70 80 90 110 120 130 140 150 170 190 210 220 232

60 70 80 90 110 120 130 140 150 170 190 210

(MQ)

(AQ)

Legend:

dual-loop detector station variable message sign gantry hard shoulder

468930225016501110(m)290 37 37



Outline




MethodologyA99 Data Summary

Detector data

DataFlow (cumulative over 1

minute)

(lane and vehicle specific)

Velocity (averaged over 1 minute)

(lane and vehicle specific)

Data availability

October 10, 2003-October 25, 2003

November 1-November 30, 2003

(57 days)

Variable Message Sign DataData Speed Limit

Driver Information

Warnings/Prohibitions

Data Availability October 10, 2003-October 24, 2003

November 11, 2003-November 30, 2003

System off October 25, 2003-November 10, 2003 (17 days)



MethodologyA99 Data Summary

Detector Data Availability

Days with VSL Days without VSL

Weekday Weekend Weekday Weekend

24 10 7 5



MethodologyTransformed cumulative curves Transformed cumulative curves (e.g. Newell, Cassidy & Windover)

– Vehicle count

– Time-averaged speed

• Transformations to heighten visual resolution:o Oblique axiso Horizontal shift with vehicle conservation

o Retain highest level of resolution (one-minute)o Identify bottleneck activations and deactivations.



Bottleneck: Definition

An “active” bottleneck is a restriction that separates upstream queued traffic from downstream un-queued traffic

An “active” bottleneck is de-activated when there is either a decrease in demand or when a queue spills back from a downstream bottleneck



MethodologyTransformed Cumulative Curves

-1,000

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

11,000

14:00 14:15 14:30 14:45 15:00 15:15 15:30 15:45 16:00

Time

N(x

,t)

Cu

mu

lati

ve

Co

un

t

N(x,t)



-1,000

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

11,000

14:00 14:15 14:30 14:45 15:00 15:15 15:30 15:45 16:00

Time

N(x

,t)

Cu

mu

lati

ve C

ou

nt


N(x,t)-q0t´

N(x,t)

q0=5180 vph




14:00 14:15 14:30 14:45 15:00 15:15 15:30 15:45 16:00

Time

N(x

,t)

Cu

mu

lati

ve C

ou

nt

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

11,000

N(x,t)-q0t´




14:00 14:15 14:30 14:45 15:00 15:15 15:30 15:45 16:00

Time

N(x

,t)

Cu

mu

lati

ve C

ou

nt

-300

-250

-200

-150

-100

-50

0

N(x,t)-q0t´



MethodologyQueuing Diagram

x1 x2

Ref. Veh. Trip Time

Number

Trip Timej

Time, t

j

t1

Travel DirectionN(xj,t)N(x1,t)

N(x2,t)



MethodologyQueuing Diagram

ExcessAccumulation

x1 x2

Time, t

Travel DirectionN(xj,t)

Excess Travel Time=Delay

N(x1,t)

N(x2,t)

t2

k



Sou

thbo

und

945

1250

1357

626

1280

1460

1540

1075

6070

8090

110

120

130

140

150

170

190

210 2

2023

2

6070

8090

110

120

130

140

150

170

190

210

(MQ)

(AQ)

468

930

2250

1650

1110

(m)

290

3737

MethodologyTime Space Diagram

Spe

ed (

km/h

r)



MethodologyTime Space Diagram

War

ning

/Pro

hibi

tion

(km

/hr)

1 = Speed 60 km/hr 2 = No passing Trucks3 = 4=



MethodologyFlow - Occupancy

All Lanes (Det. 130)

0102030405060708090

100

0 50 100 150 200

Occupancy - 5 min avg (%)

Flo

w (

vp

m)

Daily 7:40-8:00



Outline




Analysis

– bottleneck location/reoccurrence

– Bottleneck characteristics• Shock speed, prequeue, queue discharge

– Lane harmonization (flow/speed)



Go through 1 Bottleneck Diagnosis– Show audience how it is done

• Walk them through October 16, 2003 southbound– Include slides similar to A9 slides (included for

June 27, 2002)– Show how shock speed, pre-queue, and queue

discharge flows are calculated (see A9 slides)– Diagnosis

• Walk audience through 1 diagnosis– Walk audience through what VSL system was

doing



Speeds Northbound A9June 27, 2002

630



Speeds Northbound A9June 27, 2002

1



Bottleneck Activation June 27, 2002Station 380

N(x,t)-q 0t′,

q0=

51

70

ve

h/h

r

Station 380 + Off Ramp

-50

50

150

250

350

450

14:45 14:50 14:55 15:00 15:05 15:10 15:15 15:20 15:25 15:30 15:35 15:40 15:45 15:50

Time

420

390

380off

630



Bottleneck Activation June 27, 2002Stations 380–390–420

-50

50

150

250

350

450

14:45 14:50 14:55 15:00 15:05 15:10 15:15 15:20 15:25 15:30 15:35 15:40 15:45 15:50

Time @ station 420

N(x

,t)

- q

0t

420

390

380off

N(x,t)-q 0t′,

q0=

51

70

ve

h/h

r

Station 420 + On Ramp

Station 390

Station 380 + Off Ramp

Time630



-50

50

150

250

350

450

14:45 14:50 14:55 15:00 15:05 15:10 15:15 15:20 15:25 15:30 15:35 15:40 15:45 15:50

Time @ station 420

N(x

,t)

- q

0t

420

390

380off

N(x,t)-q 0t′,

q0=

51

70

ve

h/h

r

15:21@ Station 390

15:21@ Station 380

Flow

Reduction

@380


Time630



380

15:15 15:20 15:25 15:30

Time

15:21

89 km/h

70 km/h

V(3

80,t

)-b

0t′,

b0=

3300

km

/hr2

Bottleneck Activation June 27, 2002Station 380 Speed

630



-50

50

150

250

350

450

14:45 14:50 14:55 15:00 15:05 15:10 15:15 15:20 15:25 15:30 15:35 15:40 15:45 15:50

Time @ station 420

N(x

,t)

- q

0t

420

390

380off

N(x,t)-q 0t′,

q0=

51

70

ve

h/h

r

15:24@ Station 420

15:21@ Station 390

15:21@ Station 380

Flow

Reduction

@380

380

55200

55400

55600

15:15 15:20 15:25 15:30

Time

15:2189

70

V(3

80,

t)-b

0t′

, b0=

3300

km

/hr2

V(3

90,

t)-b

0t′

, b0=

4335

km

/hr2

390

98120

98170

98220

15:15 15:20 15:25 15:30Time

15:21

80 41

420

95010

95060

95110

15:15 15:20 15:25 15:30Time

V(4

20,

t)-b

0t′

, b0=

4850

km

/hr2

15:2492

65


Time630



Bottleneck Activation June 27, 2002

630

540

29400

29600

29800

15:15 15:20 15:25 15:30 15:35 15:40 15:45

Time

V(5

40,

t)-b

0t′,

b0=

4550

km

/hr2

15:349739

560

36420

36520

36620

15:30 15:35 15:40 15:45 15:50 15:55 16:00

Time

V(5

60,

t)-b

0t′,

b0=

3550

km

/hr2

15:4183 43

580

34180

34280

34380

34480

15:30 15:35 15:40 15:45 15:50 15:55 16:00

Time

V(5

80,

t)-b

0t′,

b0=

3650

km

/hr2

15:4287 43

600

32400

32500

32600

32700

15:30 15:35 15:40 15:45 15:50 15:55 16:00

Time

630

41450

41650

41850

15:45 15:50 15:55 16:00 16:05 16:10 16:15

Time

V(6

00,

t)-b

0t′

, b0=

3450

km

/hr2

15:47

72 38

V(6

30,

t)-b

0t′

, b0=

3100

km

/hr2

15:5893 20




15:21

15:24

15:34

15:4115:42

15:47

15:58 630

1

540

29400

29600

29800

15:15 15:20 15:25 15:30 15:35 15:40 15:45

Time

V(5

40,

t)-b

0t′,

b0=

4550

km

/hr2

15:349739

560

36420

36520

36620

15:30 15:35 15:40 15:45 15:50 15:55 16:00

Time

V(5

60,

t)-b

0t′,

b0=

3550

km

/hr2

15:4183 43

580

34180

34280

34380

34480

15:30 15:35 15:40 15:45 15:50 15:55 16:00

Time

V(5

80,

t)-b

0t′,

b0=

3650

km

/hr2

15:4287 43

600

32400

32500

32600

32700

15:30 15:35 15:40 15:45 15:50 15:55 16:00

Time

630

41450

41650

41850

15:45 15:50 15:55 16:00 16:05 16:10 16:15

Time

V(6

00,

t)-b

0t′

, b0=

3450

km

/hr2

15:47

72 38

V(6

30,

t)-b

0t′

, b0=

3100

km

/hr2

15:5893 20



-300

-200

-100

0

100

200

14:45 14:50 14:55 15:00 15:05 15:10 15:15 15:20 15:25 15:30 15:35 15:40 15:45 15:50

Time

N(x

,t)

- q

0t

380

350

340

320

N(x,t)-q 0t′,

q0=

51

70

ve

h/h

r

Station 350

Station 320 + Off-Ramp

Station 340

Station 380 + On-Ramp

Time @ station 380

Bottleneck Activation June 27, 2002Stations 320–340–350–380

Time630



-300

-200

-100

0

100

200

14:45 14:50 14:55 15:00 15:05 15:10 15:15 15:20 15:25 15:30 15:35 15:40 15:45 15:50

Time

N(x

,t)

- q

0t

380

350

340

320

N(x,t)-q 0t′,

q0=

51

70

ve

h/h

r

15:21@ Station 380

Flow Reduction@380

Time @ station 380


Time630



-300

-200

-100

0

100

200

14:45 14:50 14:55 15:00 15:05 15:10 15:15 15:20 15:25 15:30 15:35 15:40 15:45 15:50

Time

N(x

,t)

- q

0t

380

350

340

320

N(x,t)-q 0t′,

q0=

51

70

ve

h/h

r

15:23@ Station 350

15:27@ Station 320

15:26@ Station 340

15:21@ Station 380

Flow Reduction@380

Time @ station 380

350

40500

40600

40700

15:15 15:20 15:25 15:30Time

15:23

84

84

V(3

50,

t)-b

0t′

, b0=

4200

km

/hr2

340

22320

22370

22420

15:15 15:20 15:25 15:30 15:35 15:40 15:45

Time

15:26

99

97

V(3

40,

t)-b

0t′

, b0=

5600

km

/hr2

320

19690

19740

19790

15:15 15:20 15:25 15:30 15:35 15:40 15:45

Time

15:27

105

104

V(3

20,

t)-b

0t′

, b0=

6000

km

/hr2


Time630



Active bottleneck located between detectors 380 and 390.

Activated at 15:21. Queue propagated as far as

detector 630. Unrestricted traffic downstream.


630



Bottleneck ActivationJune 27, 2002

Direction of Travel

15:21 19:40

17:40

18:44

17:28

17:35

17:38

15:24

15:34

15:4115:42

15:47

15:58

19:18

1

630




Direction of Travel

15:21 19:40

17:40

18:44

17:28

17:35

17:38

15:24

15:34

15:4115:42

15:47

15:58

19:18

1

2

630



Direction of Travel

15:21 19:40

17:40

18:44

17:28

17:35

17:38

15:24

15:34

15:4115:42

15:47

15:58

19:18


1

2

3

630



Direction of Travel

15:21 19:40

17:40

18:44

17:28

17:35

17:38

15:24

15:34

15:4115:42

15:47

15:58

19:18


1

2

34

630




N(420,t)

N(390,t)

N(380,t)0

100

15:00 16:00 17:00 18:00 19:00

Time

N(x,t)-q0t

, q0=

51

78

ve

h/h

r

630




N(420,t)

N(390,t)

N(380,t)0

100

15:00 16:00 17:00 18:00 19:00

Time

N(x,t)-q0t

, q0=

51

78

ve

h/h

r

15:2

1 17:3

5

17:4

0

18:4

5

19:1

8

1

630




N(380,t)0

100

15:00 16:00 17:00 18:00 19:00

Time

N(x,t)-q0t

, q0=

51

78

ve

h/h

r

15:2

1 17:3

5

17:4

0

18:4

5

19:1

8

1

630




N(380,t)0

100

15:00 16:00 17:00 18:00 19:00

Time

N(x,t)-q0t

, q0=

51

78

ve

h/h

r

15:2

1 17:3

5

17:4

0

18:4

5

19:1

8

5510

vph

5370 vph

1

630




N(380,t)0

100

15:00 16:00 17:00 18:00 19:00

Time

N(x,t)-q0t

, q0=

51

78

ve

h/h

r

15:2

1 17:3

5

17:4

0

18:4

5

19:1

8

5510

vph

5370 vph

5410 vph

1 4

630



Bottleneck Activation Northbound A9Outflow Summary at 380

Day

Date

Pre-

Queue Flow

Pre-Queue

Standard Deviation

Bottleneck

Outflow Duration

Bottleneck Outflow

Bottleneck Outflow

Standard Deviation

Flow Drop

Wed 6/27/2002 5510 10.53 2:13 5370 5.8 -3% 6/27/2002 0:33 5410 6.5

Thu 6/28/2002 5800 11.22 1:41 5545 6.3 -4% 6/28/2002 0:55 5266 6.3 6/28/2002 0:30 5359 4.6 6/28/2002 1:46 5393 6.8

Mon 7/2/2002 5972 5.58 1:34 5177 6.2 -13% Tue 7/3/2002 5835 8.31 0:11 5485 4.9 -6%

7/3/2002 1:40 5017 5.2 Wed 7/4/2002 3:30 5551 6.8 Thu 7/5/2002 5527 9.43 1:22 5429 7.0 -2%

Mean: 5620 5370 -5% Standard Deviation: 320 160

630



Bottleneck Activation – October 16, 2003

Sou

thbo

und



Sou

thbo

und

9:53

8:029:44

8:18

8:25

9:29

9:28

9:497:56

8:55

10 km/hr

Pre-queue Flow = 4630 Median lane = 1848 Center lane = 1835 Shoulder lane = 948Queue Discharge Flow = 4134

Queue Discharge Flow = 4332

2

1

1 2



-200

-100

0

100

200

300

400

500

7:00 7:15 7:30 7:45 8:00 8:15

Time @ Station 60

N(x

,t)-

400

0(t

')

Bottleneck Diagnosis

Sou

thbo

und

70

60

90

80

110

120

130

140

150

170

190

210220

232

Station 130

Station 120

Station 110

Station 140 + Off Ramp – On Ramp



-200

-100

0

100

200

300

400

500

7:00 7:15 7:30 7:45 8:00 8:15

Time @ Station 60

N(x

,t)-

400

0(t')


Flow Reduction @ Station 130Uninterrupted flow between Stations 130 and 140

7:49 @ Station 130

Sou

thbo

und

70

60

90

80

110

120

130

140

150

170

190

210220

232




Continue diagnosis details for October 16 here– Similar to A9 as shown in previous slides



VSL Dynamics



VSL Dynamicsposted speed



VSL DynamicsWarnings/prohibitions



VSL Dynamicstext information



VSL DynamicsPosted speed vs Measured speed

0

20

40

60

80

100

120

140

18:3

018

:45

19:0

019

:15

19:3

0

Time

Sp

ee

d (

km

/hr)

120_AQ 120_MQ 110_AQ 110_MQ

VSL



Measured speed vs warnings prohibitions

0

20

40

60

80

100

120

140

160

180

6:00 6:15 6:30 6:45 7:00 7:15 7:30 7:45 8:00 8:15 8:30 8:45 9:00 9:15 9:30 9:45 10:00

10:15

10:30

10:45

11:00

11:15

11:30

11:45

12:00

0

1

2

3

4

5

6

7

8

9

10

11

12

13

210_MQ

210_AQ

Warnings/prohibitions



Sign AQ 215a = -1 km/hr

Sign AQ 214 = -6 km/hr

Bottleneck activation between 57-53Bottleneck shift upstream between 53-47

Bottleneck deactivated

Detector speed minus posted speed



Average trucks speeds +10-20 km/hr above mandatory 80 km/hr

Speed Variance: Trucks Detector speed (actual) – Mandatory truck speed (80 km/hr)



Speed Variance: Trucks Detector speed (actual) – Variable speed (posted)

Sign AQ 215a = -5 km/hr

Sign AQ 214 = -13 km/hr



Speed compliance

Station 120_80km/hr

0

20

40

60

80

100

120

140

160

Lane

1 Ove

rall

Lane

1 Tru

cks

Lane

1 Car

s

Lane

2 Ove

rall

Lane

2 Tru

cks

Lane

2 Car

s

Lane

3 Ove

rall

Lane

3 Tru

cks

Lane

3 Car

s

Lane

4 Ove

rall

Lane

4 Tru

cks

Lane

4 Car

s

Overa

ll

Truck

sCar

s

Av

g. S

pee

d (

km

/hr)



Flow-Density

0

1000

2000

3000

4000

5000

6000

0 10 20 30 40 50 60 70 80 90 100

Density (veh/km)

Flow

(vph

)

Det. 47 Sign Changes

Flow – Density Relationship: Detector Station 47/Message Sign AQ 214

1

2 4

3

5

N-V Curve

-19600

-19550

-19500

-19450

-19400

-19350

-19300

-19250

-19200

5:50 6:05 6:20 6:35 6:50 7:05 7:20

Time

N(x

,t)-

qo

(t')

q

o =

3800 v

ph

12700

12900

13100

13300

13500

13700

13900

V(x

,t)-

bo

(t')

b

o =

3900 k

m/h

r2

Det 47 N Det 47 V

6:14 – Speed reduced to 80 km/hr.

6:00 – Speed limit activated with posted speed of 120 km/hr.

7:05 - Speed limit de-activated. No passing restriction changes to “Congestion” indication on sign.

2448 vph

3497 vph

4197 vph

4002 vph3728 vph

3155 vph

5:55 – No passing for trucks prohibition activated 6:09 – Speed reduced to 100 km/hr

6:36 Speed reduced to 60 km/hr

92 km/hr

83 km/hr

77 km/hr 62 km/hr

76 km/hr

53 km/hr

Bottleneck activation between 57-53

120 km/hr100 km/hr80 km/hr60 km/hr

No Passing “TRUCKS ONLY” Congestion

Flow-Density points were plotted for each state at which the variable speed changed and also for constant states for detector station 47. As can be seen, the speed decreases for each point (1-5)



Sou

thbo

und

9:53

8:029:44

8:18

8:25

9:29

9:28

9:497:56

8:55

10 km/hr

Pre-queue Flow = 4630 Median lane = 1848 Center lane = 1835 Shoulder lane = 948Queue Discharge Flow = 4134

Queue Discharge Flow = 4332

2

1

1 2

WITH VSL



8:34

9:05

8:13

8:07

8:02

7:56

8:43

8:49 9:008:27

8:54

7:48

7:278:33

9:41

8:26

8:34 8:57 9:16

8:53

8:18 8:21

9:189:078:27 8:378:22

8:41

7:47 8:00

9:168:38 8:50

9:32

7:358:10

15 km/hr 20 km/hr

5 km/hr

Pre-Queue Flow = 4680 Median lane = 1740 Center lane = 1740 Shoulder lane = 1200Queue Discharge Flow = 4560

8:531

2

3

4

1

2 Pre-Queue Flow = 5340Queue Discharge Flow = 5100

WITHOUT VSL



AnalysisBottleneck Location/Reoccurrence

Include map showing all BN locations for NB and SB (next slide)

Include whether VSL was on/off Include aerial for popular locations Need to show no reoccurring and that VSL had

no impact on location Cant compare reoccurring, but still can compare

with and without VSL




Southbound

Legend

VSL ON VSL OFF




11 days of detector data with VSL system out of operation (Before Comparison)– October 25, November 1-10– 6 total weekdays of detector data with VSL system off

Statistical validness? Southbound

– Isolated bottlenecks on 3 of the days with VSL system off

– Isolated bottlenecks on 11 of the days with VSL system on

• All Non-re-occurring

• Correlated with median and shoulder lane closures and speed zone

o Construction? Maintenance of the system?



Bottleneck Characteristics

Day Pre-Queue Flow (vphpl)

Queue Discharge Flow (vphpl)

Change (%)

VSL On

October 15, 2003

October 16, 2003 1910 1610 -14%

Average x x x

VSL Off

November 2, 2003

November 3, 2003 1833 1580 -0.16

Average x x x



Consider showing figure to illustrate differences in bottleneck characteristics with and without VSL

Compare to other German, US, Canada freeways



AnalysisShock speed

Show 1 example with and without VSL Include table listing shock speeds of BN’s

– With and without VSL Are they different?

– Speed– Length– Number per day

Oscillation map? Did VSL dampen shocks

– Advise drivers upstream




15:21

15:24

15:34

15:4115:42

15:47

15:58 630

1

540

29400

29600

29800

15:15 15:20 15:25 15:30 15:35 15:40 15:45

Time

V(5

40,

t)-b

0t′,

b0=

4550

km

/hr2

15:349739

560

36420

36520

36620

15:30 15:35 15:40 15:45 15:50 15:55 16:00

Time

V(5

60,

t)-b

0t′,

b0=

3550

km

/hr2

15:4183 43

580

34180

34280

34380

34480

15:30 15:35 15:40 15:45 15:50 15:55 16:00

Time

V(5

80,

t)-b

0t′,

b0=

3650

km

/hr2

15:4287 43

600

32400

32500

32600

32700

15:30 15:35 15:40 15:45 15:50 15:55 16:00

Time

630

41450

41650

41850

15:45 15:50 15:55 16:00 16:05 16:10 16:15

Time

V(6

00,

t)-b

0t′

, b0=

3450

km

/hr2

15:47

72 38

V(6

30,

t)-b

0t′

, b0=

3100

km

/hr2

15:5893 20



Analysis

Show corridor oscillation for October 16 to help illustrate what a shock wave is

-200

0

200

400

600

800

1000

1200

1400

7:00 7:14 7:28 7:43 7:57 8:12 8:26 8:40 8:55

det. 60

det. 70

det. 80

det. 90

det. 110

det. 120

det. 130

det. 140

det. 150

det. 170

det. 190

det. 210



Shock Summary

Day Shock Speed (km/hr)

Shock Distance (km)

VSL On

October 15, 2003

October 16, 2003 1910 1610

Average x x

VSL Off

November 2, 2003

November 3, 2003 1833 1580

Average x x



Analysis – lane harmonization

Show 1 example with and without VSL Concentrate on pre-queue, during queue What are trucks doing? Speeds

– Compliance?

– What is difference in speeds across all lanes?

– Total flow for lanes What are the differences with and without VSL?



Average daily speeds on 5 days before VSL went down, 5 days with VSL down, then 5 after VSL came back on

Measure speeds at 4 stations (110-140) Need to label when and what VSL speed limits

are



Do same thing with daily standard deviation as with average speed

Station 12010.16 & 11.3

0

10

20

30

40

50

60

70

80

1:00

2:00

3:00

4:00

5:00

6:00

7:00

8:00

9:00

10:0

011

:00

12:0

013

:00

14:0

015

:00

16:0

017

:00

18:0

019

:00

20:0

021

:00

22:0

023

:00

0:00

Time

Sta

nd

ard

Dev

iati

on

Sp

eed

(km

/hr)

No VSL VSL



Station 12010.16 & 11.3

0

10

20

30

40

50

60

70

80

1:00

2:00

3:00

4:00

5:00

6:00

7:00

8:00

9:00

10:0

011

:00

12:0

013

:00

14:0

015

:00

16:0

017

:00

18:0

019

:00

20:0

021

:00

22:0

023

:00

0:00

Time

Sta

nd

ard

De

via

tio

n S

pe

ed (

km

/hr)

No VSL VSL 60 VSL 80 VSL Off



Summarize speeds at certain traffic states– Freeflow, dense, queue formation, congestion

Station 12010.16.03 & 11.3.03

8276 76 73

121115

10294

0

20

40

60

80

100

120

140

FreeFlow Dense Queue Formation Congested

Ave

rag

e S

pee

d (

km/h

r)

0

2

4

6

8

10

12

14

16

18

Sta

nd

ard

Dev

iati

on

Sp

eed

(k

m/h

r)

VSL Avg No VSL Avg VSL Std No VSL Std

Station 12010.16.03 & 11.3.03

42

65

8594

26

64

86

97

0

20

40

60

80

100

120

FreeFlow Dense Queue Formation Congested

Ave

rag

e F

low

(vp

m)

0

2

4

6

8

10

12

14

16

18

Sta

nd

ard

Dev

iati

on

Flo

w (

vpm

)

VSL Avg No VSL Avg VSL Std No VSL Std



Results

Empirical impacts of VSL system• Alteration of key traffic flow parameters

o Bottleneck location/reoccurrenceo Bottleneck properties (shock speed, pre-queue

flow, queue discharge flow)o Lane harmonization (flow/speed)

– Contribute to the minimal literature

– Potential applications on U.S. freeways • Current use in work zones



Show tables/figures summarizing results



Complications

Median and shoulder lane closures– Typical on weekdays

60 km/hr speed limit– Construction?

System unstable Limited ramp data, particularly at A9 and A94

interchanges High rates of detector failure/drift

– Vehicle conservation difficult Hardshoulder

– Difference in capacities



Outline




Outlook

Continued empirical analysis and comparison with measurements on freeways in the U.S., Canada, and United Kingdom

Improved travel time estimation and forecasting:– Traffic management

– Traveler information

– Driver assistance systems Contribute to improved traffic flow models and freeway

operational strategies Opportunity to compare with previous findings using data

from German freeways (bottleneck capacity)



Acknowledgements

Dr. Robert Bertini Dr. Soyoung Ahn Dr. Klaus Bogenberger, Dr. Georg Lerner, Dr.

Hartmut Keller, and the BMW Group Christian Mayr and Frank Frischeisen of

Autobahndirektion Südbayern



Thank you for your attention

http://www.its.pdx.edu/

analysis of variable speed limit system on a german autobahn

Documents

study areaautobahn

speed differential20

traffic sensor data

dense traffic

shoulder lane m25 u

weekday traffic volumes

german autobahnuse real

methodologya99 data