Work Zone Applications of Bluetooth Traffic Detection · Evaluate locational differences in work...
Transcript of Work Zone Applications of Bluetooth Traffic Detection · Evaluate locational differences in work...
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
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35
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45
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65
700:
001:
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0010
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11:0
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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
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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
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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 [email protected]
414-227-2150