Data through November 2012 show a
continued increase in overall traffic congestion
Kirkland, Washington – January 7,
2013 – The November 2012 aggregate score for the INRIX Gridlock Index (IGI), a
monthly measurement of road traffic congestion in 10 of the largest U.S.
metropolitan areas, is 17.7, meaning that gridlock in these cities made the
average driving trip 17.7 percent longer than necessary. Published by INRIX, a
leading international provider of traffic information and driver services, the
latest IGI score shows a sluggish yet enduring rebound in national traffic
congestion aligned with the U.S. economy’s slow recovery. At 17.7
the IGI score for November 2012 is only slightly above October’s score of 17.6,
but rising well above its historic low-point of 14.04, reached in July 2012.
“The good news is that IGI continued
to show signs of an economic recovery. However, it’s less robust than we all
would have liked, or expected, as we head into 2013,” said Bryan Mistele, CEO of
INRIX. “In fact, some of the lower IGI scores we saw from last November are
flashing yellow warning lights – for these local economies and possibly for the
nation as a whole.”
Several metropolitan areas
experienced month-over-month decreases below the aggregate level for the
U.S.:
·
Atlanta’s IGI score
decreased from 11.7 in October 2012 to 11.1 in November 2012, providing a
precautionary note to the University of Georgia Terry College of Business Dean
Robert Sumichrast’s recent prediction that the state will outpace national
economic growth in 2013.
·
Chicago’s IGI score
decreased from 15.4 in October 2012 to 13.4 in November 2012, aligned with a
slowdown also seen in the University of
Illinois’ November Flash Index, which
measures Illinois’ growth rates in corporate earnings,
consumer spending and personal income.
·
Detroit’s IGI score
decreased from 8.5 in October 2012 to 6.6 in November 2012, and was the lowest
of the Index’s 10 cities during the same period. November’s data confirm the
city’s consistent place as an IGI laggard, highlighting its deep-seated economic
issues.
The mixed economic picture captured
in the November 2012 IGI is all the more notable given the backdrop of lower
national gas prices in recent months.
While headline unemployment rates in
IGI’s 10 metropolitan areas also have declined, the high number of discouraged
workers nationwide (979,000 in November 2012) may exert downward pressure on
overall traffic congestion.
Other highlights from the latest IGI
release:
·
New
York’s November 2012 IGI score was up
20% over the previous month, possibly reflecting a rebound from the reduced
access seen in the aftermath of Hurricane Sandy.
·
A November 2012 IGI score of 17.2
shows that Boston is regaining the ground it lost after dropping from 17.23 in
September 2012 to 16.8 in October 2012. Like all of the cities in the IGI, it
has yet to retain the highs last seen in 2010.
·
Dallas’ November
2012 IGI score of 11.6 was little changed from its October 2012 score of 11.7,
remaining stable in the face of the relatively upbeat assessment seen in the
last quarterly survey of the Dallas Regional Chamber.
·
San
Francisco’s November 2012 IGI score saw a
very slight decrease month-over-month from 27 to 26.9. The tech-hub’s score
remained well above its 2012 low-point of 18.7 (observed in July).
·
Los
Angeles once again took top honors with the
highest IGI score in the nation of 31.6, meaning that gridlock forced its
drivers to endure an increase of almost 32% in the duration of their average
driving trip.
·
Miami and
Washington D.C. are the only IGI cities whose scores have
increased every month since July 2012.
IGI Scores:
November Averages
Percentage
increase in the duration of the average road trip due to
gridlock
Metro Area
November 2010 November 2011 November
2012
Atlanta
16.29 11.91
11.10
Boston
18.34 15.67
17.20
Chicago
18.59 15.27
13.40
Dallas
13.51 11.05
11.60
Detroit
8.07 7.64
6.60
Los
Angeles 38.42
29.46
31.60
Miami
16.79 15.04
15.10
New
York 25.42
21.71
25.10
San
Francisco 26.01
26.30
26.90
Washington
D.C.
23.45 18.86
18.00
Month Average:
20.49 17.29
17.70
IGI Scores:
November Year-to-Date Averages
Percentage
increase in the duration of the average road trip due to
gridlock
Metro Area
November YTD 2010 November YTD 2011 November YTD
2012
Atlanta
18.46 14.73
11.00
Boston
22.37 19.41
14.80
Chicago
23.80 18.23
14.00
Dallas
16.07 13.24
10.70
Detroit
14.53 10.43
7.20
Los
Angeles 39.90
31.85
28.90
Miami
20.69 17.26
14.00
New
York 28.40
24.35
19.70
San
Francisco 27.25
25.33
23.50
Washington
D.C.
25.09 20.20
16.50
Month YTD Average: 23.66
19.50
16.00
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 crowdsourced 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. cities. 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 markets 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:
• Reference Speed (RS): An
uncongested “free-flow” speed is determined for each road segment using the
INRIX Traffic Data Archive.
• Calculated 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
analyses.
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:
• STEP 1: For each of the 40 peak
hours, all road segments analyzed in the CBSA are checked. Each road segment
where the IGI > 0 is contributing congestion and it is analyzed
further.
• STEP 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.
• STEP 3: For each 15-minute period,
the overall metropolitan area congestion factor is the sum of the congestion
factors calculated in STEP 2.
• STEP 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.
• STEP 5: A peak period IGI is
determined by averaging the 15-minute indices from STEP
4.¬¬
About INRIX
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 35 countries.
With more than 200 customers and
partners including Audi, ADAC, ANWB, BMW, the BBC, Ford Motor Company, the I-95
Coalition, MapQuest, Microsoft, NAVIGON, Telmap, Toyota and Vodafone, INRIX’s
real-time traffic information and traffic forecasts help drivers save time every
day. visit www.INRIX.com.
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