Wisconsin Traffic Operations and Safety Laboratory

Department of Civil and Environmental Engineering University of Wisconsin-Madison

Work Zone Applications of Bluetooth Traffic Detection

FHWA Work Zone Peer Exchange Atlanta, GA

08-May-2013

John W. Shaw, PE Traffic Data & Microsimulation Manager,

Wisconsin Traffic Operatiosn and Safety Laboratory

Would You Like To…

Know when traffic in your work zone is starting to slow down? Provide travel times for alternate routes?

DOWNTOWN VIA

WORK ZONE 30 MIN ALTERNATE ROUTE 25 MIN

Would You Like To…

Compare actual work zone delay with what was predicted in the TMP/MOT? Evaluate locational differences in work

zone throughput? See how much traffic diverted to the

alternate route? See whether people who diverted

actually saved time?

What is Bluetooth?

2.4 GHz wireless system for connecting electronic devices

Low power, low cost. Range ~100 meters. High level of data/content

security. Every device has unique MAC

address. No master database of MAC

addresses. Used for traffic detection since

2008.

Image source: bluetooth.com

Bluetooth Data Collection

Bluetooth Data Collection

Detector A at 45.002, -89.9638 MAC ID 1234456890ABCDEF

07:01:05

Detector B at 45.002, -90.0044 MAC ID 1234456890ABCDEF

07:03:35

Central Server MAC ID 1234456890ABCDEF

Elapsed Time 00:02:30 Distance 2 Miles = 48 mph

Vehicle Re-Identification Process

1. “Listen” for Bluetooth MAC addresses at two or more locations.

2. Record observation time and location. 3. Transmit observations to central server. 4. Match MAC addresses spatially. 5. Compute travel time. 6. Filter out unreasonable travel times. 7. Evaluate and Report Speed, OD and Route. 8. Combine with volume data if appropriate.

Wisconsin Traffic Operations and Safety Laboratory Department of Civil and Environmental Engineering University of Wisconsin-Madison

One Detector: • Not Much

Two Detectors: • Trip Time (Speed)

Three Detectors: • Origin and Destination

Four or More Detectors: • Route Choice

A B

C

B A

A C

D B

A What Can Bluetooth Do?

Wisconsin Traffic Operations and Safety Laboratory Department of Civil and Environmental Engineering University of Wisconsin-Madison

By Itself, Bluetooth Provides…

Discrete, time-stamped observations of people/vehicles moving around.

But NOT traffic volume.

Wisconsin Traffic Operations and Safety Laboratory Department of Civil and Environmental Engineering University of Wisconsin-Madison

Field Equipment

Installation

Equipment Set-up

Cabinet-Mount Examples

Post Oak Traffic Systems

DeepBlue (TrafficNow ) BlueTOAD (Trafficcast)

BlueCompass (Acyclica)

BlueFAX (Traffax)

Other Configurations

Side-Fire (TrafficNow)

DIN Rail (TrafficNow)

Portable (Acyclica) MiniTOAD (Trafficcast)

Portable (Traffax)

Travel Time Western Milwaukee Suburbs

• 5.5 mile segment carrying 130,000 AADT

• WisDOT concerned about accuracy of DMS travel times

• Current system using data from 41 loop detectors

• Some loops reporting zero speeds

• Speeds sensitive to ongoing calibration

Findings

30

35

40

45

50

55

60

65

700:

001:

002:

003:

004:

005:

006:

007:

008:

009:

0010

:00

11:0

012

:00

13:0

014

:00

15:0

016

:00

17:0

018

:00

19:0

020

:00

21:0

022

:00

23:0

0

Aver

age

Spee

d (m

ph)

Weekday - Loops Weekend - LoopsWeekday - BlueTooth Weekend - BlueTooth

• Loop speeds low in free-flow conditions

• Loop speeds too high in congestion

• BT pairing sampling rate <3% (2010)

Recent Work Zone Field Studies

Milwaukee Portage Grafton Endeavor

Work Zone Traffic Performance

Capacity Diversion Demand

Freeway Work Zone Capacity

Why do some work zones operate better

than others?

Weekend recreational route

30+ miles 13 BT units Mainline +

Alternates Volume

counts

Rural Freeway WZ Capacity, Delay & Route Choice (Portage, WI)

Wisconsin Traffic Operations and Safety Laboratory Department of Civil and Environmental Engineering University of Wisconsin-Madison

Results: Rural Freeway Capacity

21 0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

0

500

1000

1500

2000

2500

3000

3500

0:00 4:00 8:00 12:00 16:00 20:00 0:00

Avg.

Spe

ed (M

PH)

Volu

me

(PC

E/ho

ur)

Time

Freeway Volume

Freeway Speed

PCE: Passenger Car Equivalent

Stable Flow

Queue Discharge

Recovery

~1625 PCE/hr/ln

~1450 PCE/hr/ln

Wisconsin Traffic Operations and Safety Laboratory Department of Civil and Environmental Engineering University of Wisconsin-Madison

Results: Rural Route Choice Drivers can respond to

WZ congestion in a variety of ways.

Modest increases in traffic on alternate routes

Relatively few exited and then returned to freeway.

More commonly, local traffic stayed on local routes until past the work zone.

Urban Freeway WZ Capacity, Delay & Route Choice (Milwaukee Suburbs)

Freeway Mainline + Two Alternate Routes Bluetooth Detectors + Volume Counts

Results: Urban Freeway Capacity

24

0

10

20

30

40

50

60

70

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0:00 4:00 8:00 12:00 16:00 20:00 0:00

Avg.

Spe

ed (M

PH)

PCE

(PCE

/hr)

Time

Volume (PCE) Avg. Speed

Stable Flow AM: 1825-2200 PCE/hr/lane PM: 1825-1950 PCE/hr/lane

Queue Discharge AM: 1600-1825 PCE/hr/lane PM: 1725-1825 PCE/hr/lane

Results: Urban Route Choice

Commuters very willing to use alt routes. Increased traffic on alt routes even when

mainline was not congested.

Lessons Learned

Lessons Learned

Lessons Learned

Detection rates vary by route type and time of day Since Jan 2012, USDOT requires truck

drivers to use hands-free devices.

Wisconsin Traffic Operations and Safety Laboratory Department of Civil and Environmental Engineering University of Wisconsin-Madison

Data Processing Matters

The Secret is in the Software

Options Proprietary vendor-supplied filtering and

matching services Free software from sensor vendors (basic) Third-party software (advanced)

Bluetooth vs Side-Fire Radar Bluetooth Speed (lagging) Travel time for a route

segment Accurate at all speeds Many mounting options Observes all traffic Low power consumption Requires at least 2

detectors $2500-5000 per detector Some vendors offer rental

Radar Speed + Volume Point speed at a specific

location Not accurate at low speed Pole-mount at roadside Observes specific lanes 8 to 11 watts continuous Can get data from a single

detector About $5000 per detector

Wisconsin Traffic Operations and Safety Laboratory Department of Civil and Environmental Engineering University of Wisconsin-Madison

Bluetooth Pro & Con

Inexpensive Low power consumption Highly accurate speed

data Easy to extend study

duration Efficient method for

collecting OD info Only practical way to

collect route choice data

Low sampling rates Capture rates can vary by

time of day (prob. trucks) Sometimes sensitive to:

• Site Characteristics • Antenna Placement • Loss of Power/Comm • Data processing

assumptions

Strengths Limitations

Wisconsin Traffic Operations and Safety Laboratory

Department of Civil and Environmental Engineering University of Wisconsin-Madison

Questions?

Wisconsin Traffic Operations and Safety Laboratory

Department of Civil and Environmental Engineering University of Wisconsin-Madison

John W. Shaw jwshaw@wisc.edu

414-227-2150