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Travel Time Reliability Evaluation of Recurring and Nonrecurring Congestion
Midwest Travel Model Users Group July 19, 2016
Reliability - Travel Times
2 7/19/2016
Measuring Reliability • Travel Time Data
– INRIX, Bluetooth, TICAS, etc. – Not an average!
• Nonrecurring elements – Weather – Crashes – Roadwork – Events
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Reliability– Surface Plot
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Previous SHRP 2 Work
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Reliability – CDF Curves
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0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
10 20 30 40 50 60Travel Time (minutes)
None
Weather
Event
Crash
Incident
Roadwork
Other*
*Other includes combinations of categories
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Reliability Thermometers
Existing Future
Days/Month Days/Month
Congestion Threshold
2x Free Flow Travel Time
Congestion Threshold 2x Free Flow Travel Time
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Performance Measures
Travel Time Index Travel Time Index is the ratio of the average observed travel time divided by the average free-flow travel time. Buffer Index The buffer index is the proportion of extra time (or time cushion) that most travelers add to their average travel time when planning trips to ensure on-time arrival. Planning Time Index Planning Time Index is the factor applied to the free-flow time needed to ensure on-time arrival 95% of the time. It differs from the buffer index since it includes recurring delay as well as unexpected delay.
Planning Time Failure / On-Time Measures Planning Time Failure / On-Time Measures describe the percentage of trips with travel times within a certain factor of the median travel time. Common thresholds include 1.1* Median Travel Time or 1.25* Median Travel Time. Other formulations of these measures denote the percentage of trips with average speeds below a specified threshold, for example 50 mph, 45 mph, or 30 mph.
80th Percentile Travel Time Index 80th Percentile Travel Time Index is the 80th percentile travel time divided by the free flow travel time. It represents another threshold of impacted traffic flow condition.
Misery Index Misery Index is the average of the highest five percent of travel times divided by the free flow travel time. Often referred as the 97.5% travel time index.
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𝑇𝑇𝑇𝑇𝑇𝑇 =𝑇𝑇𝑇𝑇𝑂𝑂𝑂𝑂𝑂𝑂𝑂𝑂𝑂𝑂𝑂𝑂𝑂𝑂𝑂𝑂𝑇𝑇𝑇𝑇𝐹𝐹𝑂𝑂𝑂𝑂𝑂𝑂𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹
𝐵𝐵𝑇𝑇 =𝑇𝑇𝑇𝑇95% − 𝑇𝑇𝑇𝑇𝑀𝑀𝑂𝑂𝑀𝑀𝑀𝑀
𝑇𝑇𝑇𝑇𝑀𝑀𝑂𝑂𝑀𝑀𝑀𝑀
𝑃𝑃𝑇𝑇𝑇𝑇 =𝑇𝑇𝑇𝑇95%
𝑇𝑇𝑇𝑇𝐹𝐹𝑂𝑂𝑂𝑂𝑂𝑂𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹
𝑇𝑇𝑇𝑇𝑇𝑇80% =𝑇𝑇𝑇𝑇80%
𝑇𝑇𝑇𝑇𝐹𝐹𝑂𝑂𝑂𝑂𝑂𝑂𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹
𝑀𝑀𝑇𝑇 =𝑇𝑇𝑇𝑇97.5%
𝑇𝑇𝑇𝑇𝐹𝐹𝑂𝑂𝑂𝑂𝑂𝑂𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹
Previous SHRP 2 Work
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0
5
10
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45
50
0
50
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2006 2007 2008 2009 2010 2011 2012
Volu
me
(100
0 AD
T)
Dela
y (1
000
hour
s) None
Weather
Event
Crash
Incident
Roadwork
Other
Volume
Previous SHRP 2 Work
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• Approximately 800 directional miles – Freeways -- 4 and 6 lanes – Rural two-lane highways – Urban arterials
• 3 years of Travel Time Data – 1 to 5 min. intervals
• ATR Continuous Volume Data
• Sites with highest combined volumes and crashes received priority
• 90% used for model development 10% used to verify and calibrate
WisDOT Reliability
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Travel Time Equations
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0
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20
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70
0 1000 2000 3000 4000 5000 6000 7000 8000
Spee
d (m
ph)
Demand (pce/hr)
Freeway Corridor with 65 mph FFS
Normal Conditions
Snow Conditions
Crash
Incident
Crash + Snow
Incident + Snow
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Snow Frequencies
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0%
5%
10%
15%
20%
25%
Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec
Aver
age
Freq
uenc
y
Snow – Northwest Region
Snow
• Average Frequencies developed for each month by weather region
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Crash Risk Distribution
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y = 1.7689e0.0007x R² = 0.9146
0
5
10
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30
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0 500 1000 1500 2000 2500 3000 3500 4000 4500
Cras
h O
bser
vatio
ns p
er 1
000
Volu
me
Occ
urre
nces
Volume
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Predictive Reliability Example
0.0%
1.0%
2.0%
3.0%
4.0%
5.0%
6.0%
7.0%
8.0%
0
10
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0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000
VMT
Dist
ribut
ion
Spee
d (m
ph)
Demand (vph)
2040 No Build VMT
2040 Build VMT
4-Lane Speed
6-Lane Speed
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I-35W Managed Lane
• 8 segments in study area • Travel time and volume data
– Year 2014 (every day)
– 15-minute intervals
• Non-recurring conditions data – MnCMAT crash data
– NOAA weather data
1
2
Project Area Study Area
Reliability Segments
3
5
6
7
8
4
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Project Alternatives
No Build HOV / MnPASS Gen Purpose
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Southbound – 2040 No Build
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Southbound – 2040 GP
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Southbound – 2040 MnPASS
MnPASS Lane
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Southbound Reliability – AM Peak
2040 GP 2040 MnPASS (GP Lanes)
2040 MnPASS (MnPASS Lane)
2040 HOV (GP Lanes)
2040 HOV (HOV Lane)
North of Lexington Ave to Mississippi River Days/Month Days/Month Days/Month Days/Month Days/Month
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Northbound Reliability – PM Peak
2040 GP 2040 MnPASS (GP Lane)
2040 MnPASS (MnPASS Lane)
2040 HOV (GP Lanes)
2040 HOV (HOV Lane)
Mississippi River to North of Lexington Ave Days/Month Days/Month Days/Month Days/Month Days/Month
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-
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
45,000
50,000
Add General Purpose Add MnPASS Add HOV
Peak
Per
iod
Pers
on T
rips
Reliability by Person Trips - Peak Period/Peak Direction
4.0 x Free Flow
3.5 x Free Flow
3.0 x Free Flow
2.5 x Free Flow
2.0 x Free Flow
1.5 x Free Flow
Free Flow
Managed Lane
Reliability Comparison
12,000
21,000
18,000
Increase reliability by 9,000 trips
Additional 4,000 people throughput
Travel Times
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I-494/TH 62 Congestion Relief
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TH 169 Mobility Study
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NB
PTI Delay (hr) RR Weather
RR Crash
RR PTI Delay (hr) RR Weather
RR Crash
RR
1.33 44 92% 77% 33% 3.42 446 41% 19% 16%
2.30 78 89% 75% 67% 2.20 136 76% 51% 8%
2.06 162 66% 51% 50% 0.97 2 100% 99% N/A
1.40 60 91% 81% 70% 1.30 39 95% 87% 50%
Excelsior
Old Shakopee
CR 69 Notes: Tuesday – Thursday only
Planning Time Index (PTI) = 𝑇𝑇𝑇𝑇95%𝑇𝑇𝑇𝑇𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹
Delay is the average total delay (for all vehicles) for the peak period in hours Reliability Rating (RR) = 𝑇𝑇𝑂𝑂𝑇𝑇𝑇𝑇𝑂𝑂𝑇𝑇𝑇𝑇<1.25∗𝐹𝐹𝐹𝐹𝑇𝑇𝑇𝑇
𝑇𝑇𝑂𝑂𝑇𝑇𝑇𝑇𝑂𝑂𝑡𝑡𝐹𝐹𝑡𝑡𝑡𝑡𝐹𝐹
N/A = Insufficient Data
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Previous Applications
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Scott County Congestion
Performance Measures
AM Peak
Reliability/ Congestion Map
Data Source: NPMRDS
7/19/2016
Reliability Resources Upcoming Activities • Minnesota Reliability Outreach (Fall 2015)
Online Resources • SHRP 2 Website
– Publications, Tools, and Webinars • Travel Time Reliability Reference Manual
– Online Wikibook by Michael Janson 7/19/2016 27