Latest INRIX Gridlock Index (IGI) Drives Optimism for the U.S. Economy in 2013
-- Decline in Traffic Congestion Slows in December Signaling Better Economy --
KIRKLAND, Wash., Jan. 31, 2013
KIRKLAND, Wash., Jan. 31, 2013 /PRNewswire/ -- Despite the hustle and bustle
of the holidays, the INRIX Gridlock Index (IGI) shows drivers spent less time
in traffic in December 2012 versus the same period one year ago. Compared to
the dramatic 20 percent drop in traffic congestion year-over-year from
December 2010 to December 2011, gridlock declined just three percent
year-over-year in December 2012.
"For the first time in several years, we've avoided a complete freefall in
December traffic congestion," said Bryan Mistele, CEO of INRIX. "The results
suggest the economy finally may be turning the corner."
The December IGI numbers follow a 15 percent increase in traffic congestion in
November – the first monthly increase in nearly two years. Recent IGI trends
mirror the latest data from the Conference Board's Leading Economic
Index®(LEI), which rose by half a percent in December.^1
The latest IGI score also included some good news from an unexpected source.
Detroit, historically an IGI underperformer, was among the metropolitan areas
measured that defied the seasonal effect which normally sees traffic fall from
November to December. Detroit's gridlock increased by almost 10 percent
month-over-month; by contrast the IGI composite for all 10 metropolitan areas
fell by approximately 14 percent. This may be a positive signal for Detroit's
economy, in line with recent reports that housing prices in some Detroit
neighborhoods may be rebounding^2, and that the number of auto manufacturing
jobs in the city has increased by 27 percent since 2009^3 (the year that
General Motors filed for bankruptcy protection).
The nine remaining metropolitan areas examined by IGI experienced
month-over-month decreases in traffic congestion in December. In particular:
oAtlanta's IGI score decreased from 11.1 in November 2012 to 9.3 in
December 2012. On a year-over-year basis its December 2012 IGI score
decreased by nearly 14 percent. While slightly improved from the
year-over-year change seen in December 2011 (-16.7 percent), it may be of
little comfort to those already unsettled by former CNBC Chief Economist
Marci Rossell's recent observations that the region may have experienced a
oBoston's IGI score decreased month-over-month by almost 19 percent, from
17.2 in November 2012 to 14 in December 2012. However, on a year-over-year
basis its December 2012 IGI score increased by 5.4 percent, significantly
improved from the year-over-year change seen in December 2011 (-27.5
percent). This is in line with the Federal Reserve's report of moderate
economic growth in its most recent "Beige Book" survey of the region.^5
oDallas' IGI score fell by 17 percent month-over-month to 9.6 in December
2012. On a year-over-year basis its December 2012 IGI score changed by
-9.1 percent, deteriorating from the year-over-year change seen in
December 2011 (-5.6 percent).
oChicago experienced the largest month-over-month decline of all IGI
metropolitan areas. Chicago's IGI score decreased over 24 percent, from
13.4 in November 2012 to 10.2 in December 2012. This was likely influenced
by a major winter storm that struck the region the week before Christmas.
On a year-over-year basis its December 2012 IGI score changed by -16.9
percent, an improvement from the year-over-year change seen in December
2011 (-27.7 percent).
The latest composite IGI score was captured against a backdrop of slightly
lower national gas prices in December.
IGI Scores: December Averages
Percentage increase in the duration of the average road trip due to gridlock
Metro Area December 2010 December 2011 December 2012
Atlanta 13.0 10.8 9.3
Boston 18.3 13.2 14.0
Chicago 16.9 12.2 10.2
Dallas 11.2 10.6 9.6
Detroit 12.8 5.8 7.2
Los Angeles 36.3 29.8 27.7
Miami 14.5 13.4 12.9
New York 25.7 20.4 21.8
San Francisco 27.4 23.3 23.7
Washington D.C. 22.0 16.9 15.6
Overall: 19.8 15.7 15.2
INRIX Gridlock Index (IGI) Methodology
The INRIX Gridlock Index draws data from the INRIX Traffic Data Archive
http://scorecard.inrix.com/scorecard/, a historical traffic information
database comprised of data collected from hundreds of public and private
sources, including a crowd-sourced network of approximately 100 million
vehicles and mobile devices.
Drawing on almost three years of trend data, INRIX has developed methods to
interpret real-time traffic data to establish monthly and annual averages of
traffic patterns in all major U.S. metropolitan areas. These same methods can
aggregate data over periods of time to provide reliable information on speeds
and congestion levels for given segments of roads. Using this proprietary data
collected from INRIX's extensive network, the IGI analyzes and measures
traffic trends in 10 of the top metropolitan areas in the U.S. The
metropolitan areas used in the IGI are defined by the Core-Based Statistical
Areas (CBSA), as determined by the United States Census Bureau.
There are two key building blocks for the analysis used in the IGI:
oReference Speed (RS): An uncongested "free-flow" speed is determined for
each road segment using the INRIX Traffic Data Archive.
oCalculated Speed (CS): Speed data from the INRIX Traffic Data Archive is
analyzed to determine the "calculated speed" for each 15-minute period of
each day, for each road segment every month (e.g. Monday from 06:00 to
06:15 for April 2012). Thus, each road segment has 672 corresponding
calculated speed values per week – representing four 15-minute time
windows for each hour of the day, multiplied by seven days in a week.
To assess congestion across a metropolitan area, INRIX utilizes and adapts
several concepts that have been used in similar studies and previous INRIX
The IGI represents the barometer of congestion intensity. For a road segment
with no congestion, the IGI would be zero. Each additional point in the IGI
represents a percentage point increase in the average travel time of a commute
above free-flow conditions during peak hours. An IGI of 30, for example,
indicates a 20-minute free-flow trip will take 26 minutes during the peak
travel time periods, which is a 6-minute (30 percent) increase over the
free-flow travel time.
For each road segment, an IGI Index is calculated for each 15-minute period of
the week, using the formula IGI= (RS/CS) – 1.
"Drive Time" Congestion: To assess and compare congestion levels year to year
and between metropolitan areas, only "peak hours" are analyzed. Consistent
with similar studies, peak hours are defined as the hours from 06:00 to 10:00
and 15:00 to 19:00, Monday through Friday – 40 of the 168 hours of a week.
For each metropolitan area, an overall level of congestion is determined for
each of the 40 peak hours by determining the extent and amount of average
congestion on the analyzed road network. This is computed as follows, once
IGI's are calculated for each road segment:
oSTEP 1: For each of the 40 peak hours, all road segments analyzed in the
CBSA are checked. Each road segment where the IGI is greater than 0 is
contributing congestion and analyzed further.
oSTEP 2: For each road segment contributing congestion, the amount the IGI
is greater than 1 is multiplied by the length of the road segment,
resulting in a congestion factor.
oSTEP 3: For each 15-minute period, the overall metropolitan area
congestion factor is the sum of the congestion factors calculated in STEP
oSTEP 4: To establish the metropolitan IGI for a given 15-minute period,
the metropolitan congestion factor from STEP 3 is divided by the number of
road miles analyzed.
oSTEP 5: A peak period IGI is determined by averaging the 15-minute indices
from STEP 4.
INRIX® is a leading traffic intelligence platform delivering smart data and
advanced analytics to solve transportation issues worldwide. INRIX
crowd-sources real-time data from approximately 100 million vehicles and
devices to deliver traffic and driving-related insight, as well as
sophisticated analytical tools and services, across five industries in 32
With more than 200 customers and partners including Audi, ADAC, ANWB, BMW, the
BBC, Ford Motor Company, the I-95 Coalition, MapQuest, Microsoft, NAVIGON, O2,
Tele Atlas, Telmap, Toyota and Vodafone, INRIX's real-time traffic information
and traffic forecasts help drivers save time every day.
^2 The Detroit News. "Metro Detroit property values buoy hopes."
^3 NPR. "Tiny Chevrolet Sonic helps Detroit shake off rust." 1/04/2013.
^4 Atlanta Business Journal. "Atlanta's Lost Decade." 1/10/2013.
Contact: Jim Bak, INRIX, +1 (425) 284-3825, firstname.lastname@example.org; Jeniece Primus,
Brunswick Group LLC on behalf of INRIX, +1 (415) 671-7676,
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