Sanhita Lahiri, P.E., PTOE
Virginia Department of Transportation [email protected]
USING ANALYSIS AND VISUALIZATION
TO GET YOUR POINT ACROSS
Simona Babiceanu,
University of Virginia [email protected]
Computation and
Visualization of Historic
Congestion Trends on
Virginia Interstates During
Major Holiday Travel Periods
VASITE
2014 - SUMMER
Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Introduction
Data Analysis Methodology
Visualization – Desktop and Mobile
Challenges
Q & A
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Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Data
Focus – Interstates within Virginia
Data Used – Latest 3 years from INRIX
Granularity – 1 minute aggregated to 30-
minutes
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Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Data Analysis – Prepare Data for Averaging
Standard deviations (STDV) of speeds over latest 3
years were calculated at 1-minute intervals and a
threshold STDV was chosen
The 1 minute data for every Traffic Message
Channels (TMC) was averaged to 30 minute
An “STDV Test” was performed for each TMC
o Speed Data with STDV below threshold was
“Ready” to be averaged across three years
o Speed Data above threshold STDV was
considered Outlier data and several steps were
performed to get it “Ready”
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Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Data Analysis – Interim Steps to Eliminate Outliers
Remaining outlier data was normal (“ready”)
for a TMC if
o All three individual yearly speeds had same
Congestion Level
o Only one of three possible yearly pairs had
STDV below threshold. The outlier speed was
eliminated and speeds from the other two years
were used.
o The outlier speed was matched with only one
incident. The speed from incident year was
eliminated.
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Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Mainline Congestion Threshold
Based on experience, posted speed limits,
rural or urban area and roadway gradient,
speed thresholds were assigned to different
levels of congestion
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Speed Limit Threshold Congestion Level
Urban (60
mph or 55
mph)
55 mph or above Little to No Congestion
between 45 and 54 mph Moderate Congestion
less than 45 mph Heavy Congestion
Rural (65
mph or 70
mph)
63 mph or above Little to No Congestion
between 45 and 62 mph Moderate Congestion
less than 45 mph Heavy Congestion
Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Outlier Elimination
Remaining outliers were eliminated based on
values from their neighbors.
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Congestion Level
Little to No Congestion
Moderate Congestion
Heavy Congestion
Outliers
Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Outlier Elimination
Remaining outliers were eliminated based on
values from their neighbors.
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Congestion Level
Little to No Congestion
Moderate Congestion
Heavy Congestion
Outliers
Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Data Smoothing
Single cells completely surrounded by cells of different
congestion levels were changed to match neighbors.
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Congestion Level
Little to No Congestion
Moderate Congestion
Heavy Congestion
Outliers
Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Data Smoothing
Single cells completely surrounded by cells of different
congestion levels were changed to match neighbors.
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Congestion Level
Little to No Congestion
Moderate Congestion
Heavy Congestion
Outliers
Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Final Result
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Congestion Level
Little to No Congestion
Moderate Congestion
Heavy Congestion
Outliers
Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Local Feedback
Manual Adjustments based on comments and special
conditions
o RHOV lanes
o I-495 Express Lane Construction
o I-564 connecting I-64 to the Norfolk Naval Base
o I-581 in Roanoke
o I-77 (Mountainous area)
o Downtown Tunnel in Hampton Roads with
Flashing Posted Speed Limits
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Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
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Outlier Stats
Percent outliers at the end of each data
processing step
Holiday
Standard Deviation Threshold
STDV> Threshold
Not the Same Congestion Level
After Elimination of Outlier Speed
After Incident Mapping
TG 2012 5 mph 12.1 10 2.9 2.8
MD 2013 3.5 mph 10.5 7.2 2.3 2.2
TG 2013 4 mph 11.7 8.6 2.6 2.5
MD 2014 4 mph (mainlines) 7 mph (ramps)
7.6 5.8 1.6 1.5
Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Data Analysis and Field Verification Challenges
Inadequate Ramp Data
Adjusting Map based on Field Validation
Influence of truck speed on TMC speed on
mountains
INRIX data quality, availability and coverage
Understanding Drivers Expectations amidst
various travel information available
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Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Online Google Maps Website
Congestion level data and geometry KML files
were loaded into Google Fusion Tables.
Congestion level color corresponds to a
specific road segment (TMC) and time period.
Website
Custom GM JavaScript API v3 code, HTML, jQuery
Interactive, easy-to-use, time-aware (slider, Prev/Next
buttons)
Custom interstate shields
Legend
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Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Website code: time-awareness, interstate shield
layer, KML selection by zoom level, map coloring
are achieved with custom code.
Shapefile pyramid: shapefiles for each level of
zoom created from basic, undistorted shapefile.
Distortion: offset between the two directions
Manual corrections necessary to remove artifacts and
achieve visually pleasing results
Ramps and RHOV only at high levels of zoom
(zoomed in)
Time consuming, laborious, trial and error process
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Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Mobile Version – Goal
Website with same URL as desktop version
o Automatic detection when accessed via
mobile device
Maximizing code sharing and easy migration
o Maximizing code sharing with desktop
version
o Easy migration to work with different
datasets e.g. Memorial day weekend (4 days),
Thanksgiving (5 days)..
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Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Mobile Version – Working Parameters
GUI designed to cover mainstream mobile
devices on the market and display graphics
consistently
Operating Systems: iOS, Android, Windows
(Phone)
Different versions of OSs – e.g., iOS 6, iOS 7
Browser: Safari, Chrome, IE Mobile, Firefox,
etc.
Hardware: Mobile phones, Tablets, etc.
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Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Mobile Version
Design of Mobile friendly GUI functions
o Showing map on a small screen, yet
highlighting the pertinent features for the user
Cross mobile devices compatibility
o Dealing with various screen resolutions, e.g.
320 X 480 to 1920 X 1080 and higher
o Customizing web components based on the
device screen size / resolution
o Dealing with mobile OS migration issues, such
as from iOS 6 to iOS 7
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Computation and Visualization of Historic Congestion Trends
On Virginia Interstates During Major Holiday Travel Periods
Preview
http://people.virginia.edu/~seb4v/Thanksgiving2013 http://people.virginia.edu/~seb4v/MDW2014
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