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Modeling at CMAP
INRO Model City Portland 2016 Conference
September 20, 2016
CMAP’s Models
•
•
•
Trip-based model
– Conformity
– Small-area traffic forecasts
Activity-based model
– Highway pricing
– Transit policy
Freight model
– Freight policy
Trip-Based Model
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8 highway scenarios for different times of day
2 transit scenarios (AM Peak for work trips, off-peak
for non-work trips)
Standard 4-step procedures, with Emme handling trip
distribution and network assignment
Activity-Based Model
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•
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8 highway scenarios
8 transit scenarios
Emme network skims feed CT-RAMP synthetic
population activity scheduler
CT-RAMP output trips fed back to Emme for final
assignment
Agent-Based Supply
Chain Modeling Tool
• Development driven by
•
policy questions asked in GO
TO 2040
Need a freight modeling tool
that explains the economic
choices made for goods
movement across multiple
modes and commodities
National Supply Chain
Model
• Estimates annual commodity
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•
flows between firms
Does not just apportion FAF
flows
FAF is one possible future –
we want a flexible tool for
scenario testing
– Macroeconomic conditions
– Transport and logistics costs
– Business operating strategies
How the National Supply
Chain Model Works
• Generate a set of firms
•
•
representing all businesses
in the country
Match Buyers to prospective
Sellers
Simulate business
transactions
CMAP Freight Model Zone
System
CMAP Freight Model Inland
Waterways Network
CMAP Freight Model
Highway Network
CMAP Freight Model Rail
Network
CMAP Freight Network
Costs
The Emme network is skimmed to provide:
• Zonal distances specific to each mode and
rail carrier
• Information on which zone pairs are served
by which modes
These costs are some of the components of
the transport and logistics cost formulation
used by the freight model.
Planning Factors – Who Benefits?
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Use not proximity
Identify trips
General or highly selective
Any market or vehicle class
Can also be used for transit
Assignment speed and
travel time validation
• National Performance Management Research Data Set
(NPMRDS) provided through Federal Highway
Administration
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Average travel time by directional Traffic Message
Channel (TMC) Code segments
Data reflect 2013 and are reported for fifteen minute
periods
Coverage includes National Highway System and other
principal arterials
Assignment speed and
travel time validation
• Network conflation process – coverage overlays
Assignment speed and
travel time validation
• Travel speed comparison
Arterial
Freeway
Assignment speed and
travel time validation
• Travel time comparison
Assignment speed and
travel time validation
• Travel time comparison (trips < 15 miles)
Assignment speed and
travel time validation
• Travel time comparison (trips >= 15 miles)
Assignment speed and
travel time validation
• Travel time contours
Congestion
enumeration
• Traditionally use volume-to•
•
capacity ratio to define
congestion
Road segments flagged as
entirely congested or entirely
uncongested
Fine for estimating aggregate
levels of congestion on a
regional scale, but what
happens at the project level?
Congestion
enumeration
• Aggregation error occurs
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•
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when comparing minor
differences
Results from assumption
that all vehicles on a
segment travel at the same
average speed
3.3% reduction in average
speed contributes a
disproportionate 8.3%
congested vehicle miles
Even more so with
congested vehicle hours
On a one mile road segment with a
capacity of 6,000 vehicles per hour
during the two hour AM peak:
Vehicles Speed
Assigned (MPH)
Congested
11,000
60
No
13,000
58
Yes
Congestion
enumeration
• Empirically, vehicles move at
•
•
•
a variety of speeds
Enumerate vehicles and
assign a speed to each
Amount of source data for
congestion statistics is
multiplied significantly
(number of links * number of
vehicles)
More continuous transition
between “uncongested” and
“congested” for any given
segment
Congestion
enumeration
• Export assignment results
•
•
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from Emme, using Modeller
to create a network shapefile
Randomly assign speeds
using distribution based on
the segment average
Designate a congested
speed threshold (e.g. 4 MPH
below free-flow)
Flag vehicles with speeds
below the threshold as
experiencing congestion
Congestion
enumeration
• Tested by comparing change in CVHT between build and
no-build project scenarios using volume-to-capacity ratio
method and enumeration method
CVHT NB
1,313.0
2,619.5
Enumeration
VC
CVHT B
511.4
1,079.6
18000
CONGESTED
16000
14000
12000
10000
Vehicles
NB
8000
B
6000
4000
2000
0
42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
Speed
Congestion
enumeration
• So far, results are inconclusive
• The different methods give different answers, closer for
•
some projects than others
Which answer is more accurate?
Congested VC Ratio
Congested Enumeration
VC > 0.9
5336 directional links
Congested Volume > 90%
2415 directional links
Thank you
•
Nick Ferguson
– [email protected]
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Craig Heither
Claire Bozic
Noel Peterson
Aaron Brown
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