1. Network Attributes Calculator
TRB Application Conference, Raleigh, NC
May 15, 2017
Vipul Modi, Citilabs Inc.
Greg Giaimo, Ohio DOT

2. Project Motivation Tasks included:
Ohio Department of Transportation (ODOT) has been automatically calculating capacity and speed attributes using Highway Capacity Manual (HCM) procedures for travel demand model networks for 25 years which are used for both traditional link based and junction based assignment
Tasks included:
update procedures from HCM 2000 to HCM 2010
convert FORTRAN codes to Cube Voyager
add roundabout capabilities
expand stop-sign computations
add freeway weaving adjustments
expand geometrical aspects of networks

3. History First, created for Steubenville MPO networks in 1993
based on HCM 1985 procedures
for consistence capacities values across networks for validation
Updated to CAP94 program
based on HCM 1994 procedures
included several other MPO networks
Updated to CAP2000 program
based on HCM 2000 procedures
used for networks in Ohio-Kentucky-Indiana region
Ran as user-programs executables (.exe) in regional models

4. Components of Network Calculators
Network Preparation
Geometry
Capacity Calculator
Speed Calculator
Turn Penalty File Writer
Junction File Writer
Final Outputs
An external loop to process the data for different time periods

5. Current Network Calculators

6. Network Preparation
conduct data consistency/completeness checks, flag inconsistent or incomplete network coding
see next to see what conditions were flagged
handle how the period specific over-ride attributes are used and how many times the outer loop should run
if over-rides are not specified, default (daily) attributes are used
write a network diagnostic summary file for the users’ reference

7. Network Preparation

8. Geometry
this step determines the geometry of subject link by accessing link attributes from adjoining links
step identifies the next intersection node or a conflict point
conflict point is a node with > 2 links using a ‘downstream tracing algorithm’
used to carry over attributes of the intersection link to all links leading to subject link
calculate distance between subject link and conflict point
computes true shape angles between links
used to obtain turn movements – left/through/right
to be used in urban street capacity calculations

9. Geometry
used to identify merging/diverging points for freeway merging analysis
computes freeway weave length
Obtains information on type of intersection, like two-way stops, four-way stops, roundabouts, or signals
computes distance between two intersection nodes to calculate capacities
If distance is >2 mile, then uncontrolled, if <2 mile, controlled

10. Capacity Calculator
Process to calculate capacity values for network links
old process computes capacities for freeway segments, multi-lane roads, rural highways, uninterrupted 2 lane facilities and interrupted urban segments using HCM 2000 procedures
uses all necessary information like number of lanes, width, facility type, area-type, left/through/right lanes, parking lanes, etc coded in the network links or from the user-specified parameter file
cross-street attributes obtained from geometry step to identify different type of urban street capacity calculations
capacity computed for each time-period depending upon period-specific over-rides

11. Capacity Calculator
current process includes HCM 2010 equations for basic freeway segment capacity calculations, multi-lane and two lane highways
inclusion of total ramp density
current process includes enhanced capacity values for two-way stop, four-way stop and roundabouts
capacities computed in a spreadsheet with all possible scenarios using HCM 2010 methodologies
based on geometric conditions, uses a lookup table to get the respective capacity values
current process computes capacities for 5-link intersections
virtually assuming a 4-link and 3-link intersections

12. Capacity Calculator current process includes freeway weaving analysis
reduction factors are calculated that ‘reduces’ capacity due to weaving
spill-over factors applied to upstream/downstream freeway links and ramps
handles 4-link zero distance freeway-links

13. Speed Calculator
old process updates base speeds on basis of link attributes and cross street attributes to obtain the final free flow or running speeds
base speeds by facility type provided by ODOT
current process incorporates free flow speed adjustments from Chapter 17 of HCM 2010 that uses area-type, distance between two consecutive signals (from geometry step), and two-way-left-turn lane coding
speeds computed for each time-period depending upon period-specific over-rides
two set of speeds based on total time and running time
compute link groups for each link used in highway assignment
used in selecting the volume delay function (VDF) for link flow speed adjustments

14. Turn Penalty Writer
writes turn penalty files in {A-B-C-value-set} format
append any existing turn prohibitions that the user provide
use the geometry information to get all left-turn movements and give them a user-specified penalty value
default turn penalty – 0.2
one turn penalty file for all time periods

15. Junction File Writer
writes junction file for each node based on adjoining links information
use of turn prohibitions for banning movements
current process includes:
new junction format based on HCM 2010 methodologies for two-way stops, four-way stops, roundabouts
introduction of new signal phases
split phasing based on link attributes
forced left-turn phases or prohibition of left-turn phases
write junction files for each time period

16. Final Outputs
clean-up working network for the next loop (time period) and reset all temporary link attributes
change attribute names for capacity, speeds, link group as per ODOT standards

17. Other…
an outer loop to handle how many times the calculators should run based on over-ride link attributes
capacities, speeds, linkgroups are computed for all AM, MD, PM and MD time periods
flexible scenario manager to turn on/off following options:
options to compute network utilities based on ‘old process’ or ‘new process’
options added to also use old format ODOT networks
use of true-shapes in angle calculation
managing output files
parameter file (for default or user-over ride variables ) supplemented as external file

18. Software Additions (Cube Voyager)
New Keywords added to NETWORK module

19. Software Additions (Cube Voyager)
New Keywords added to NETWORK module

20. Software Additions (Cube Junction Model)

21. Moving forward…
such automated network attribute computation from base attributes (LANES etc.) facilitates more detailed network operations modeling
calculated values allow for both traditional VDF controlled link- based and more detailed junction based assignments
transition to DTA much easier for ODOT as a result
current enhancements continue the trend of adding more operational level detail in the planning networks

22. Acknowledgments
Ohio Department of Transportation (ODOT)
Greg Giaimo
Rebekah Anderson

23. Questions/discussion