NATMEC 2014
New Jersey Department of Transportation
NATMEC 2014
Improving Traffic Data Collection, Analysis and Use
New Jersey Pilot Study
Testing Potential MAP-21 System Performance Measures
June 30, 2014
NATMEC 2014
What We’ll Cover Today
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Project Approach
Pilot Corridors
Data Sources
Performance Measure Calculations
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Variations
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Annual Hours of Delay
Reliability Indexes
Thresholds
Measurement Unit
Aggregation
Results
Wrap-up
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Issues & Challenges
Other Considerations
Possible Next Steps/Recommendations
June 30, 2014
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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NATMEC 2014
Project Approach
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Test system-level performance measure methodologies
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For two NJ corridors (Interstate, arterial)
Test AASHTO recommended measures for delay and reliability
Propose/test alternate formulations
Test alternate thresholds
Evaluate aggregation methods
Assess results – what the values are telling us
Note barriers, challenges, assumptions,
workarounds
Develop a Summary Report
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Outline step-by-step procedures
 Present results, “lessons learned”
 Provide recommendations
June 30, 2014
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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NATMEC 2014
Pilot Corridors
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Chosen based on regional importance, unique features and familiarity
Interstate; rural to urban; portion
with local & express lanes; toll & free
78-C
78-B
78-A
78-D
• Entire length – 67.8 miles
• Divided into 4 sub-corridors:
- PA border to I-287 (30.8 miles)
- I-287 to GSP (22.6 miles)
- GSP to NJ Tpk (5.4 miles)
- NJ Tpk to Holland Tunnel (9.0 miles)
18-D
NHS freeway & arterial; limited
access & traffic signals; urban,
commercial, semi-rural
18-C
• Entire length – 45.3 miles
• Divided into 4 sub-corridors:
18 -B
18-A
June 30, 2014
- NJ 138 to GSP (14.3 miles)
- GSP to US 9 (16.1 miles)
- US 9 to NJTPK (9.5 miles)
- NJTPK to Hoes Lane (5.4 miles)
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Testing Potential MAP-21 System Performance Measures
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Data Sources
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Travel Time (Speed) Data
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Vehicle Probe Project (VPP) Suite
(Massive Raw Data Downloader)
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Five-minute average -- reliability
Hourly average -- delay
Vehicle Probe Project Suite
Vehicle/Truck/Bus
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NJDOT Congestion Management System (NJCMS)
 NJ TRANSIT General Transit Feed Specifications
(GTFS)
 NJDOT Weigh-in-motion (WIM)
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Vehicle Occupancy
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Plan4Safety (Crash database)
 NJ TRANSIT (Bus load factors)
June 30, 2014
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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NATMEC 2014
Performance Measure
Calculations
Annual Hours of Delay (AHD) & Reliability
June 30, 2014
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Testing Potential MAP-21 System Performance Measures
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Annual Hours of Delay (AHD)
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Compare hourly travel times with threshold travel time
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Consider options for “Agency-specified” thresholds
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Delay Time = Travel Time in excess of threshold
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Delay = Delay Time x Volume (vehicles/persons/trucks/buses)
AASHTO Method
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Hourly travel times for an “Average Week”
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Calculate delay for an average week, multiply by 52
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TMC delays can be aggregated to sub-corridors and corridors by adding
Alternate Method
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Concern: “Average Week” data underestimates annual delay
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If particular Avg TT < Threshold TT, Delay Time = 0
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But individual day TT for that time of day, day of week
Proposal: Use hourly data for each day of the year
June 30, 2014
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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NATMEC 2014
Reliability
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AASHTO Reliability Index (RI80)
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RI80 = Maximum TT80/Threshold TT
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In words: TT multiplier to ensure on-time arrival 80% of the time if you happen to
be traveling in the most congested 5-minute period, compared to a threshold TT
for that segment, regardless of time of day
Alternate Method (TTRMax)
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Concerns: RI80 threshold TT does not reflect congested conditions; most
unreliable time of day may not be most congested time of day; extreme values
for RI80 (>7, <1)
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Proposal: TTRMax = max (TT80/TT50)
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In words: TT multiplier to ensure on-time arrival 80% of the time, if you happen to
be traveling in the most unreliable 5-minute period of the day, compared to a
median travel time for that segment for that five-minute period
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Denominator doesn’t have to be median, but should vary with time (otherwise is
the same as RI80)
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This method give less extreme values
June 30, 2014
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Testing Potential MAP-21 System Performance Measures
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NATMEC 2014
Comparative Example – RI80 vs. TTRMax
TMC 120P04419
4.5
Travel Time, minutes
4
TT80
TT50
3.5
3
Max TT80 = 4.19 min (7:50 AM)
Free-flow TT = 0.56 min
Annual Median TT = 0.59 min
RI80 = 7.1 or 7.5
2.5
2
Max TT50 = 1.73 min (7:55 AM)
1.5
1
0.5
0
2:00 AM
4:00 AM
6:00 AM
8:00 AM
4:00 PM
6:00 PM
8:00 PM
10:00 PM 12:00 AM
TTRMax = 4.8 (8:55 AM)
TT80 = 3.32 min
TT50 = 0.69 min
6
TTR
TTR = TT80/TT50
10:00 AM 12:00 PM 2:00 PM
Time of Day
5
4
Maximum unreliability is not at the same
time as maximum 80th percentile travel time
3
2
1
0
12:00 AM
2:00 AM
June 30, 2014
4:00 AM
6:00 AM
8:00 AM
10:00 AM 12:00 PM 2:00 PM
Time of Day
4:00 PM
6:00 PM
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
8:00 PM
10:00 PM 12:00 AM
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Variations
Thresholds  Measurement Unit  Aggregation
June 30, 2014
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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Threshold Variations
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Free-flow travel time
Use calculated 15th percentile travel time (using 5-minute data)
 Same as travel time at 85th percentile speed
 Implies that freely flowing roadways are “goal”
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Median travel time over all days
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Single value, but similar to free-flow travel time, unless always congested
Median travel time by day of week and hour of day
Reflective of “expected” conditions by time of day & day of week
 May be more appropriate for reliability threshold than delay threshold
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Maximum throughput travel time (at 85% of the posted speed)
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Based on Washington State DOT practice
“Acceptable” travel time
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Percentage of free-flow travel time that
varies based on area type and time of day
 Context-sensitive
Area Type
Urban
Suburban
Rural
Percent of Free-flow Travel Time
Peak
Off-peak
167%
133%
133%
118%
111%
105%
All thresholds capped at speed limit
June 30, 2014
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Testing Potential MAP-21 System Performance Measures
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Threshold Comparison For Average Week
Example Link A
"Acceptable" TT
(TMC 120+04411)
Maximum Throughput TT
3
Median TT, all days
2.8
Freeflow TT
Median TT, day/hr
Travel time, min
2.6
Average TT
2.4
2.2
2
1.8
1.6
1.4
Sun 12 AM
Mon 12 AM
Tue 12 AM
Wed 12 AM
Thu 12 AM
Fri 12 AM
Sat 12 AM
Sun 12 AM
Day of week and hour of day
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Testing Potential MAP-21 System Performance Measures
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Measurement Unit Variations
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Vehicles (vehicle-hours, vehicle-miles)
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Person (person-hours, person-miles)
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Measures the total people moved
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Auto passengers
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Bus passengers
Buses
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Measures only the number of vehicles moved
Where PMs impact buses
Trucks
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Sub
corridor
2008-2010
Vehicles
2008-2010
Occupants
AVO
78A
4,202
5,958
1.42
78B
4,987
6,542
1.31
78C
3,075
4,248
1.38
78D
2,280
3,198
1.40
18A
781
990
1.27
18B
755
965
1.28
18C
3,424
4,673
1.36
18D
1,546
2,015
1.30
Where PMs impact trucks
June 30, 2014
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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NATMEC 2014
Aggregation Variations
TMC
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Corridor
Delay (Units of Hours)
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Sub-Corridor
Simple addition
Reliability (Indices)
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Reliability measures are “unit-less”, cannot be added together
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Option 1: Weighted Averages
Many possibilities for TMC weights:
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Link length
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Daily vehicle miles traveled (VMT)
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Median travel time
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Daily person miles traveled (PMT)
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Daily vehicle volume
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Daily vehicle hours traveled (VHT)
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Daily person volume
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Daily person hours traveled (PHT)
Option 2: Calculate reliability directly at sub-corridor/corridor level (by direction)
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Add up travel times for entire sub-corridor/corridor
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Calculate statistics and index values similar to TMC level
June 30, 2014
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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NATMEC 2014
Results
Corridor/Sub-Corridor for AHD and Reliability
June 30, 2014
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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AHD Results Example: I78 (TMC-level)
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Shown in Person-Hours
of Delay/mile
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¯
Free-flow Threshold
Hourly Person Volume x
Travel Time above threshold
Person Volume =
Vehicle Volume x AVOSubcorr
+ Bus Passengers
Over all days
N
78-C
78-D
Legend
APHD/mile (Freeflow Threshold)
47 - 25,000
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Varying Threshold
Travel Time Creates
Different AHD Results
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Free-flow travel time
Maximum “thru-put” travel time
(85% of posted speed)
Additional thresholds not
shown
 Yearly median
 Day/Hour median
 “Acceptable” travel time
0
0.75
1.5
3 Miles
25,000 - 50,000
50,000 - 100,000
100,000 - 654,000
¯
Max. Thru-put Threshold
N
78-C
78-D
Legend
APHD/mile (Max Thruput)
0 - 25,000
0
0.75
1.5
3 Miles
25,000 - 50,000
50,000 - 100,000
100,000 - 1,430,000
June 30, 2014
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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AHD Threshold Variation Results
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Varying threshold travel time results in different outcomes
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No consistent pattern
Each threshold option has unique policy implications for “delay”
Annual Person-Hours of Delay
per mile (thousands)
140
120
100
80
60
40
20
0
18
Corridor
Free-flow
June 30, 2014
18A
18B
Yearly Median
18C
18D
78
Corridor
Max Throughput
78A
78B
“Acceptable” Speed
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
78C
78D
Day/Hr Median
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RI80 Threshold Variation Results
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Varying Threshold
Travel Time Creates
Different RI80 Results
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Free-flow travel time
Yearly Median travel time
Maximum Throughput travel
time (85% of posted speed)
Extreme values
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Values under 1.0
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Worst 80th percentile TT <
threshold TT
Not a logical multiplier
Set to 1.0
Legend
1.00
1.01 - 1.20
1.21 - 1.50
1.51 - 2.00
2.01 <
Values above 7.0
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June 30, 2014
Worst 80th percentile TT >
seven times threshold TT!
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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NATMEC 2014
Alternate Formulation (RI80 vs. TTRMax)
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TTRMax gives more moderate (realistic?) values than RI80
on a TMC basis…
AASHTO Formula
Alternate Formula
June 30, 2014
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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NATMEC 2014
Alternate Formulation (RI80 vs. TTRMax)
Reliability Alternatives
Median Threshold - Aggregated with PHT Weights
2.8
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…but differences are
less pronounced on a
corridor or subcorridor level
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
RI80
June 30, 2014
TTRMax
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Testing Potential MAP-21 System Performance Measures
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Wrap-up
Issues & Challenges  Other Considerations
 Possible Next Steps/Recommendations
June 30, 2014
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Testing Potential MAP-21 System Performance Measures
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Issues & Challenges – General
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MS Access has 2 GB file size limitation
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Use multiple databases with linked tables
 Alternatively, use an enterprise DBMS (e.g., SQL, Oracle) or statistics
package (e.g., SPSS, SAS)
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Manual conflation of TMCs (for volumes) tedious and timeconsuming
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NJCMS missing hourly volumes by day of week, especially
weekends
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Hopefully a one-time process
Currently assuming average weekday hourly volumes apply to all 7
days
Determining how to “aggregate up” TMCs for “telling the story”,
particularly for reliability
June 30, 2014
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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NATMEC 2014
Issues & Challenges – NJ Specific
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Lacking traffic volume data in NJCMS for 128 miles of the enhanced
NHS (need to find out coverage of INRIX and NPMRDS/here data)
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Accounting for transit ridership is problematic:
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Tedious process to use GTFS tables to get number of NJ TRANSIT
buses on each TMC during each hour for weekday and weekends
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Applying typical peak/off-peak loading factors to get number of
passengers
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Missing private and university bus data
NJDOT Specific
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IT/OIT (Hardware/Software/Bandwidth) – significant tech issues
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Staff Knowledge/Skill Sets – rapidly evolving tech/data difficult to keep
up with; using AOD creatively to “tell the story” challenging for most
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Time – current workload/staffing makes taking on new, complex work
difficult; department-wide attrition also a factor
June 30, 2014
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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NATMEC 2014
Other Considerations
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Why PM changes occur (may be difficult to quantify and could affect target-setting)
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Complex issues re signalized arterials
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Signal spacing/side friction
Multiple speed curves
Algorithms are evolving (makes trending tricky)
Functional class
More critical thinking needed re: “agency-determined threshold travel times”
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Project effectiveness?
Change in background traffic growth?
Economy boom or bust?
Gas prices?
Across performance measures
Across agencies
Analytical tools HIGHLY DESIRABLE
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Automates the process
Minimizes errors
Speeds production
Creates consistent summary output (tables, graphs, visualizations)
June 30, 2014
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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NATMEC 2014
Possible Next Steps/Recommendations
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Look at multiple years to see what changes in PMs occur
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Temporally
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Spatially
Test corridors/years where there have been recently completed
projects
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Have other States and MPOs run through similar tests
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“Telling the story” about project effectiveness
Varying levels of resources, tools, expertise, etc.
Test the PM methodologies using NPMRDS datasets
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Data completeness, integrity, etc.
June 30, 2014
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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NATMEC 2014
Thank you!
Questions
Comments
Discussion
Keith Miller, Principal Planner
Data Analysis & Forecasting
kmiller@njtpa.org
June 30, 2014
John C. Allen, Section Chief
Bureau of Commuter,/Mobility Strategies
john.allen@dot.state.nj.us
NJ Pilot Study
Testing Potential MAP-21 System Performance Measures
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