bus signal priority based on gps and wireless communications · bus signal priority based on gps...

1

Bus Signal Priority Based on GPS and Wireless Communications

Chen-Fu LiaoMinnesota Traffic Observatory

Department of Civil EngineeringUniversity of Minnesota

Gary DavisDepartment of Civil Engineering

University of Minnesota

ITS Advanced Transportation Technologies Seminar Series, September 25, 2007

Outlines

uBackground

uPhase I - Simulation Study

uPhase II – Prototype system development

2

What is Transit Signal Priority (TSP)?

“A tool to help make transit service more reliable, faster, and more cost effective. It has little impact on general traffic and is an inexpensive way to make transit more competitive with the automobile.”

- ITS America TSP planning and implementation handbook

“ Transit signal priority systems use sensors to detect approaching transit vehicles and modify signal timings to improve transit performance. ”


Priority vs. Preemption

uSignal priority modifiesnormal signal operation process to accommodate transit vehicles

uPreemption interrupts the normal signal operation process for special events (railroad crossing, emergency vehicles)

3

Transit Signal PriorityDetection Technologies

u Advantage: § Compatible with commonly used loop detectors§ Relatively reliable§ Does not require line-of-sight or visibility

u Disadvantage: § Require in-pavement loop detectors§ Prone to failure due to pavement flexing

u Example: v IDC LoopComm

u Implementation: v LA, Chicago

Inductive loop-based detection


u Advantage: § Widely used in U.S. for EVP, § Well tested for many years

u Disadvantage: § Require Line-of-sight clearance between emitter and

detectoru Example:

v 3M Opticom, Optronix/Tomar Strobecom, Novax Bus Plus

u Implementation: v Oakland, Tacoma, Portland, Vancouver

Light-based (Infrared) detection

4


u Advantage: § Emergency vehicle does not need additional equipment§ Facilitate inter-jurisdictional emergency response§ Does not require line-of-sight or visibility

u Disadvantage: § Not practical for transit signal priority (need additional

audible siren)§ False activation from building/car alarms

u Example: v Sonic Sonem 2000, EPS II

Sound-based detection


u Advantage: § Does not depend on line-of-sight or visibility

u Disadvantage: § Require RD tag installation at upstream curbside§ None directional vehicle information (with no RF tag

installation)u Example:

v TOTE (RF Tag), Econolite (EMTRAC)u Implementation:

v King County Seattle

Radio-based detection

5


Satellite (GPS)-based detectionu Advantage: § Does not depend on line-of-sight or visibility§ Can easily notify controller when vehicle has cleared

u Disadvantage: § Slow AVL polling rate§ Low/no GPS reception in urban canyon

u Example: v 3M GPS Opticom

u Implementation: v City of Edinburg, TX?

TSP Experiences in USAn Overview of Transit Signal Priority, ITSA

6

Transit Signal Priority (TSP)Background

u Bus signal priority has been implemented in several US cities (Seattle, Portland, LA, Chicago, St. Cloud, etc.)*

u Metro Transit performed tests on Lake Street using 3M Opticom technology (problem w/ nearside bus stops & trigger timing)

u Metro Transit contracted SEH Inc. to conduct TSP conceptual design along Northwest (Bottineau) corridor

u Most TSP deployments use sensors to detect buses at a fixed or preset distance.

* An Overview of Transit Signal Priority, ITS America 2002

Adaptive Bus Signal Priority Objectives

u Provide efficient and reliable bus transit service to traveling public.

u Reduce transit operation cost.u Use already installed GPS/AVL on bus & a

wireless communication based adaptive signal priority system with minimum impact on other traffic.

u Conduct traffic modeling and simulation to analyze and evaluate the possible impact.

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u Bus transmits signal priority request to traffic controller based on its readiness not presence.

Bus Signal PriorityOur Approach

I am ready…

Bus Signal PriorityOur Approach (continue)

u Adaptive bus signal priority strategy using GPS/AVL and wireless communication technology.

u Provide conditional signal priority based on bus’s schedule adherence, speed, location and estimated dwell time at bus stop.

u Transmit priority request wirelessly from bus to intersection signal controller.

u Evaluate benefits and impacts of signal priority from simulation model.

8

Key Features of Our Approach

u Non-proprietary wireless communication (802.11x protocol)

u Use existing GPS/AVL system on busu Incorporate passenger count and bus lateness

to provide conditional priorityu Consider bus stop dwell time for signal priority

request when it is ready (Intersection arrival time forecast)

u Include controller phasing and timing status in priority request, forecast and decision making

Study Site – Franklin Ave. Minneapolis

27th Ave Dupont Ave. 3 miles, 22 signalizedintersections

Hiawatha LRTI-35W

To I-94& I-394 I-94

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Simulation Model Development

u Intersection Capacity Analysis (Synchro)uData CollectionvSignal timing plan (from Minneapolis)vVolume and turning movements (Use Jamar)vTravel time (Vehicle probe)vBus dwell time & delay (20%) at intersectionvBus stop location (GIS from Metro Transit)

uUse AIMSUN Micro-Simulator

Simulation Model Development (con’t)

uCapacity Analysis

10


uNetwork Modeling


uNetwork Model Calibration08:00 ~ 08:15AM EB

Reaction Time = 0.75s, Reaction Time at Stop = 0.8s

0

50

100

150

200

250

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41

Detector Station (42 intersections)

15-m

in V

olum

e

EB SIM EB BAL

Franklin Avenue Eastbound

11

Signal Priority Strategy

Intersection i

Intersection i-1 Intersection i+1

Bus Stop j Bus Stop j+1Eastbound

Westbound

Busde, j

de, i

Bus Stop kBus Stop k+1dw, k

dw, i

Bus Stop k-1Bus

Bus Stop j-1

Far side bus stop

Nearside bus stop

Signal Priority Request

delaybrb

jeaj TT

vd

T ++×

=467.1

,

bv : is bus speed, in MPH.

jed , : is the distance from the current bus location to bus stop j, in feet.

brT : is bus braking/stopping time.

delayT : is the traffic delay on bus route.

uNearside Bus StopAverage bus travel time to stop j:

12

Signal Priority Request

bv : is bus speed, in MPH.

: is the distance from the current bus location to intersection i, in feet.

delayT : is the traffic delay on bus route.

uFar side Bus Stop

Average bus travel time to intersection i:

delayb

iwai T

vd

T +×

=467.1

,

iwd ,

Poisson Distribution(Lambda=3)

0.000

0.050

0.100

0.150

0.200

0.250

1 3 5 7 9 11 13 15

Number of Passenger

Prob

abili

ty

Bus Dwell Time Calculation

uDwell Time Forecast at Bus Stop

[ ] boardingkkjB

dj TjtjttT ×−×= − )()()( 1λ

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Signal Priority Acknowledgement

uRequest Time, TF (Time factor)vFirst come first serve

uBus Schedule Adherence, LF (Lateness Factor)vLF=0 if bus is ahead of schedule

uNumber of Passenger, PF (Passenger Factor)

Signal Priority Treatment: Green Extension

Cycle iPlan 1 2

Priority Phase

3 4 1

Cycle iPlan 2 2

Priority Phase

3 4 1

Priority Request

Green Extension

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Signal Priority Treatment: Red Truncation

Cycle iPlan 1 2

Priority Phase

3 41

Cycle iPlan 2

2

Priority Phase

3 41

Priority Request

Early Green Extension

Signal Priority Treatment: Phase Insertion

Cycle iPlan 1 2

Priority Phase3 4 1

Cycle i+1 2Priority Phase

3 4 1

Priority Request

Cycle iPlan 2 2

Priority Phase3 4 1

Extension

2

Resynchronization

15

Signal Priority Strategy Modeling

GETRAM EXTAPI Interface

AIMSUNTraffic Simulator

Bus arrival/travel timeestimation model

Passenger arrival model at each stop

Intersection signalphasing/timing model

Signal priority, recovery, resynchronization model

Traffic Controller Model

Bus Signal PriorityController

Bus dwell time model at each stop

Bus SignalPriority Strategy

Read intersectionand bus stop data

Acquire bus(k) location,compare its distance to

next stop(j) and intersection(i)

dist2NextStop>dist2NextIntsc ?

Far side bus stop Nearside bus stop

Estimate time when buswill pass next signalized

intersection

t_estimate - sim_time<= system response time ?

No

Estimate bus dwell, arrivaltime at bus stop and travel

time to next intersection

dist2BusStop <=system response distance ?

Submit priority requestusing green extensionor red truncation for

intersection (i)

No

NoYes

Yes Yes

Exit extension phase and return back to phasep+1, where p is the phase before extension

Resynchronize signaltiming at next cycle

GETRAM APIInterface

TrafficSimulator

Is intersection (i)priority enabled ?

Yes

No Wait for next signalizedintersection with enabled

signal priority strategy

Signal Priority Control Flowchart


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Bus Signal Priority Phase I Simulation Study Results

u Bus travel time reduction v AM-Peak: 12-15% v PM-Peak: 4-11%

u Bus delay time reductionv AM-Peak: 16-20% v PM-Peak: 5-14%

Overall Network Measures

Network Flow and Speed

19.818.0

13.497

18.128

0

5

10

15

20

25

Flow (1000 veh/h) Speed MPH

Ave

rage

Sta

tistic

s

AM Peak PM Peak

Network Travel and Delay Time

0:01:35

0:01:00

0:01:55

0:01:20

0:00:00

0:00:17

0:00:35

0:00:52

0:01:09

0:01:26

0:01:44

0:02:01

Avg. Travel Avg. Delay

Ave

rage

Tim

e

AM Peak PM Peak

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Bus Travel Time and Speed (AM Peak)

AM Peak Bus Speed

9.1

10.4

9.2

10.7

8

8.5

9

9.5

10

10.5

11

No Priority With Priority

Ave

rage

Spe

ed M

PH

EB WB

AM Peak Bus Travel Time

0:16:27

0:19:53

0:17:30

0:19:02

0:14:24

0:15:07

0:15:50

0:16:34

0:17:17

0:18:00

0:18:43

0:19:26

0:20:10


Trav

el T

ime

EB WB

Bus Travel Time and Speed (PM Peak)

PM Peak Bus Speed

9.2

7.7

8.38.3

6.5

7

7.5

8

8.5

9

9.5


Ave

rage

Spe

ed M

PH

EB WB

PM Peak Bus Travel Time

0:21:580:22:41

0:19:39

0:21:03

0:14:24

0:15:50

0:17:17

0:18:43

0:20:10

0:21:36

0:23:02

0:24:29


Trav

el T

ime

EB WB

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MOE Analysis of Major Intersections

uHennepin – No significant changeuLyndale – 10% decrease in delay & stopsuNicollet – about 30%increase in travel

time and 47% increase in delayuChicago – about 5% decease in travel

time & delay timeuCedar - about 24% increase in travel time

and 30% increase in delay

Video Clip

With Priority

Without Priority


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Phase II Study Overview

uDevelop wireless communication prototype using commercial off-the-shelf (COTS) product

u Implement & validate GPS/AVL and wireless communication based signal priority strategy

uField testing and validation

Phase II Prototype Systems

AntennaModemTx/Rx

AntennaModemTx/Rx

PriorityRequestServer(PRS)

PriorityRequest

Generator(PRG)

GPS/AVL

APC

I/O

TrafficController

OBURSU

VID, # Passenger, Stop Location,Schedule, Door Status, etc.

Ref: NTCIP 1211 V01.37 Protocol

Ex. Door Open/Close

GPS 18

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Signal Priority System Hardware

RSUOBU

GPS Receiver

Controller Cabinet

NEMA Controller

AMD GX500256 MB RAM

Signal Priority Embedded System

Embedded System

Radio Modem

PC

Power Converter

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Wireless Communications

uMinneapolis Wi-Fi Network

u5.9 GHz WAVE Radio

Minneapolis Wi-FiImplementation StartNovember, 2006

Phase OneAnticipated Completion................................................June, 2007

Phase TwoAnticipated Completion......................................September, 2007

Phase ThreeAnticipated Completion..........................................October, 2007

Phase FourAnticipated Completion..........................................October, 2007

Phase FiveAnticipated Completion......................................November, 2007

Phase SixAnticipated Completion......................................December, 2007

http://www.usiwireless.com/service/minneapolis/schedule.htm

30-40 nodes/sq mile

http://www.usiwireless.com/service/minneapolis/schedule.htm

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5.9 GHz Radio

Denso WAVE (Wireless Access in Vehicular Environment) Radio Module Prototype

u Bandwidth: 75 MHz (5.850 ~ 5.925 GHz) u 5.89 GHz (IEEE 178, control channel)u Channels: 10 MHz per channel (20 MHz optional)

Frequency (GHz)

5.85

0

5.85

5

5.86

0

5.86

5

5.87

0

5.87

5

5.88

0

5.88

5

5.89

0

5.89

5

5.90

0

5.90

5

5.91

0

5.91

5

5.92

0

5.92

5

5.82

5

5.83

0

5.83

5

5.84

0

5.84

5

US Spread Spectrum Allocation

Uplink

Downlink

IEEE DSRC Standard, http://www.ieee802.org

PublicSafety/Private

Public SafetyIntersectionsControl

ChannelPublicSafety/Private


US and Potential Mexican DSRC Allocation

IntersectionsControl Veh-Veh

Dedicated Public Safety

Short Rng ServiceMed Rng Service

Shared Public Safety/Private


PublicSafety

Veh-Veh

5.9 GHz DSRC Band Plan

http://www.ieee802.org

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Bus Stop & Intersection Geo-Database

Bus route #2Travel Pattern #1

Test Plan and Data Collection

uEquip a passenger vehicle for initial testing

uWireless communication reliability and latency data collection and analysis

uSignal priority algorithm verification and validation

uFinal testing and validation (one bus + one intersection)

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Acknowledgement

§ ITS Institute, University of Minnesota.§ Don Sabania and Scott Tacheny at City of

Minneapolis.§ Gary Nyberg, John Levin at Metro Transit.§ Hun-Wen Tao & Wu-Ping Xin, CE students.§ Priya Iyer, EE student.§ Ted Morris & Pi-Ming Cheng at ITS Institute.§ Tony Juettner at Brown Traffic Products, Inc.

Thank You Very Much!

I am ready…

bus signal priority based on gps and wireless communications · bus signal priority based on gps...

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