30th CAITR University of Western Australia December 12, 2008 Robert L. Bertini and Huan Li Conference for the Australian Institutes of Transport Research

30th CAITR • University of Western Australia December 12, 2008

Robert L. Bertini and Huan Li

Conference for the Australian Institutes of Transport Research University of Western AustraliaDecember 11, 2008

Exploiting High Exploiting High Resolution Archived Resolution Archived Transit Data for Transit Data for Improved Planning and Improved Planning and Operations: A Portland, Operations: A Portland, Oregon Case Study Oregon Case Study


Portland Founded 1851 530,000 in city 2 million people in metro area

145 mi2

173 ft above sea level

78 miles to Pacific Ocean

65 miles to Palmer Glacier on Mt. Hood

36 in annual rainfall

Largest wheat export port in U.S.

38 breweries inside metro area

No sales tax No self-serve gas

Distance between Perth and Portland:9,231 miles (14,854 km)



145 mi2











145 mi2










About TriMet Serves 1.2 M population

575 mi2

63.9 M annual bus trips

207,700 daily bus boardings

95 bus routes 655 buses 8100 bus stops Also LRT, Commuter Rail, Streetcar & Paratransit


TriMet’s Bus Dispatch System

On-BoardComputer

Radio

DoorsLift

APC (Automatic Passenger Counter)Overhead Signs

OdometerSignal Priority Emitters

Stop Annunciation

Memory Card

RadioSystem

Garage PC’s

Radio AntennaGPS Antenna

Navstar GPS Satellites

Control Head



Schedule deviation

Control HeadControl Head

PCMIA CardPCMIA Card

Infrared APCInfrared APC

Operator InputOperator Input

DispatchingDispatching Arrival PredictionArrival Prediction


Stop Data

TIME LINE

DWELLTIME

DO

OR

OP

EN

DO

OR

CL

OS

E

ARRIVE TIME

LEAVE TIME

REWRITTEN ARRIVE TIME (IF DOOR OPENS)

STOP LOCATION

15 METERS

30 METERS




Stop Data

Ro

ute

No

.

Serv

ice

Date

Leave T

ime

Sto

p T

ime

Arr

ive T

ime

Bad

ge

Dir

ecti

on

Tri

p N

o.

Lo

cati

on

ID

Dw

ell

Do

or

Lif

t

On

s

Off

s

Est.

Lo

ad

Max S

peed

Patt

ern

D

ista

nce

X C

oo

r.

Y C

oo

r.

14 01NOV2001 8:53:32 8:49:15 8:53:28 285 0 1120 4964 0 0 0 0 0 21 41 10558.58 7644468 67600514 01NOV2001 8:55:00 8:51:41 8:54:46 285 0 1120 4701 4 0 0 0 1 20 50 15215.05 7649112 67632814 01NOV2001 8:56:22 8:52:00 8:55:08 285 0 1120 4537 36 3 0 6 0 26 34 15792.35 7649674 676220

Route Number Vehicle Number Service Date Actual Leave Time Scheduled Stop Time Actual Arrive Time Operator ID Direction Trip Number Bus Stop Location

Dwell Time Door Opened Lift Usage Ons & Offs (APCs) Passenger Load Maximum Speed on

Previous Link Distance Longitude Latitude


PORTAL Database

Loop Detector Data20 s count, lane occupancy, speed from

500 detectors (1.2 mi spacing) since 2004

Incident Data140,000 since 1999

Weather DataHourly since 2004

VMS Data19 VMS since 1999

Bus Data1 year stop level data 2007

140,000,000 rows

Web Interfaceportal.its.pdx.edu


2007 AM Boardings


Passenger Movement


Fare Evasion


Background on Stop Location

• Challenges in delivering reliable and timely bus service

• Financial constraints• Public transit operational issues• Transit service generally favors bus stop

accessibility• Sometimes based on past history and tradition

rather than rigorous ongoing analysis at the stop level


Stop Spacing Service Standards

TriMet • Portland >80 units/acre: 400-600 ft 22-80 units/acre: 500-750 ft 4-22 units/acre: 600-1000 ft <4 units/acre: as needed Inner Portland has 200 ft blocks (264 ft street spacing) Route 19 mean stop spacing is 942 ft (3 blocks)


Concept DerivationTrade off: person’s time in parallel access vs.

another person’s time in riding. •Minimize access cost: favors small s•Minimize riding cost: favors large s


Assumptions• Origins & destinations distributed along route

in one dimension (ignore perpendicular access)…

• Average access distance (parallel only) =s/4

• Assume number of passengers boarding or alighting at a stop to be ~Poisson distributed


Access Cost Value of Passenger Travel Distance

• p = density of trip origins plus density of trip destinations for passengers who board or alight the same vehicle (units: number/distance)

• s/4= average access distance (unit: distance) ν = passenger access speed (unit: distance/time) a = average cost per unit time per person for access

(unit: cost/time)

ps2a

4vin interval of length s

Ca= [avg. no. of pax] [avg. dist traveled] [cost/unit dist]

s

4

ps

av


Riding and Stopping CostValue of in-vehicle passenger lost time due to boardings and alightings

• N = expected number of passengers on vehicle• V = vehicle cruise speed = time lost in stopping to serve passengers• Pr =1-e-ps = probability that vehicle actually stops (from

Poisson for number of ons and offs) r= average cost per unit time per person for riding

N= in interval length s

Cr= [avg. no. of pax] [riding time + lost time][cost/unit time]

s

V+Pr

r

=NsrV

+Nr(1 e ps )


[ ] / s

Average Cost Per Unit Length

Given that

[access]

= 4ravpN

Average cost per unit length

+ [riding] + [stopping]

= ps2a

4v

NsrV

+Nr(1 e ps)

Average cost per unit length =

V

NpN r

r

Independent of s !

Choice of s is independent of V, depends solely on

ps

eps ps )1(


Objective Function

ps

epsC

ps )1(0

Coverage for >2

If β > 2:ps

e ps )1( ps

1


ps

psC

10

p

N

p

Npv

ps a

r

44

ps = expected number of passengers to board or alight per stop

nsDestinatio and Origins Trip ofDensity

Buson Pax No.ofTimeLost 4Spacing Optimal

ps

psC

10


Case Study: Inbound Route 19 All Day

• 370 days (2/20/07 - 1/5/08)

• 19,344 trips• 33.2 ons and offs/trip:• Average passenger load/stop:

7.9

• Route 19 Glisan to Portland• Route Length: 9.27 mi• Number of stops: 52• Mean delay due to stopping:

33.6 s• Use 4ft/s walking speed


343

780

1,26

42,

045

807

1,49

955

179

359

996

6 1,01

783

760

581

971

0 758 80

5 859

762

1,02

464

879

61,

096

623

613

638

660

890

861

505

991

420

704

630 76

179

31,

187

782

565

974

726 81

42,

768

1,95

072

81,

579

528

2,10

889

02,

479

952

460

0

500

1,000

1,500

2,000

2,500

3,000

0.0

0.1

0.2

0.5

0.8

1.0

1.3

1.4

1.5

1.6

1.8

2.0

2.2

2.3

2.4

2.6

2.7

2.9

3.0

3.2

3.4

3.5

3.7

3.9

4.0

4.1

4.2

4.3

4.5

4.7

4.8

5.0

5.0

5.2

5.3

5.4

5.6

5.8

6.0

6.1

6.2

6.4

6.5

7.1

7.4

7.6

7.9

8.0

8.4

8.5

9.0

9.2

9.3

9.5

Distance Along Route Toward Downtown (miles)

Bu

s S

top

Sp

acin

g (

ft)

0

2

4

6

8

10

12

14

Nu

mb

er

of

Passen

gers

Route 19 Inbound Spacing Status


Optimized Spacing Calculation• No. of passengers on vehicle N = 7.9 pax/stop• Passenger ons and offs ps = 33.2 pax/trip• Lost time =33.6sec


QuickTime™ and a decompressor

are needed to see this picture.

2007 Time Space Passenger Load Plot Route 19

Time (hour)

Dis

tanc

e (m

i)

30

25

20

15

10

5

0

9

8

7

6

5

4

3

2

1

05 10 15 20


0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

0 10 20 30 40

N (number of passengers on bus)

Sto

p S

pac

ing

(ft

)

Route 19 Inbound Optimized Spacing

Optimal

February 20, 2007–January 5, 2008For n = 790,392, = 33.6 sec, = 22.8 sec (range 1-100)Mean ons/offs = 33.2Also shown are spacing plots for 20, 40 and 60 ons/offsStep function based on 20 blocks/mile

20 ons/offs

60 ons/offs

40 ons/offs

20 blocks/mile

33.2 ons/offs


Sensitivity Analysis1/2 1/3 1/4

Optimized Spacing (ft) 1728 1411 1222

Access Cost

Value of access time ($/hr) $ 16/hr $ 18/hr $ 20/hr

Before optimized (passenger $/unit length) $ 0.64 $ 0.72 $ 0.80

After optimized (passenger $/unit length) $ 1.18 $ 1.08 $ 1.04

Change (passenger $/unit length) +0.54 +0.36 +0.24

Riding Cost

Value of riding time ($/hr) $ 8/hr $ 6/hr $ 5/hr

Before optimized (passenger $/unit length) $ 2.30 $ 1.72 $ 1.44

After optimized (passenger $/unit length) $ 1.83 $ 1.50 $ 1.32

Change (passenger $/unit length) -0.47 -0.22 -0.12

ar


Conclusions• 12 stops are recommended for consolidation• The trip time would be reduced by 3.4 min/trip• The total savings due to consolidation could be up

to 3.7 hours of service time per day • Allow the addition of approximately 7.6 additional

trips per weekday • Mean weekday headway would drop from 18.0 min

to 16.1 min • Total of 17,076 inbound trips, the time saved would

be 977 hours during the year • Assuming $60/hr operating cost, about $60,000

could be saved by TriMet


Next Steps• Route 19 AM Peak Inbound (TRB 2009), PM Peak

Outbound

• Automate process for all routes

• Produce quarterly reports for TriMet

• Verify “real” cost savings

• Consider “real” relationship to demand and equity

• Connect to scheduing


Acknowledgements• Huan Li, Ph.D. Student• David Crout of TriMet

for providing the rich data set that facilitated this analysis

• Gordon Newell• Prof. Michael Cassidy,

University of California at Berkeley, for his assistance in developing the analytical framework for this paper

[email protected]

Documents

30th CAITR University of Western Australia December 12, 2008 Robert L. Bertini and Huan Li Conference for the Australian Institutes of Transport Research