7.1 VERSION NERPMAB1v2

This section documents the improvements that were made to the NERPM model since the adoption of the model as part as the “Path Forward 2040” Long Range Transportation Plan. The improvements focused on improving its usability related to runtime, user’s catalog interface, and model usability

Runtime

The investigation of alternative methods to reduce system run times focused on the highway network assignments and global feedback iterations. After investigating several different options for reducing runtime the following improvements were made:

Feedback Loops

The transition of model outputs from one feedback loop to the next one and feedback loop termination criteria were adjusted in the new model. The model has been set up such that the weighted-average volume for each link is calculated at the end of each loop, based on the current and previous feedback loop flows. These averaged volumes are used to generate skims for the next iteration of the model system and are fed back to the demand models (DaySim).

In addition, rather than terminate based on a fixed number of iterations, the model has been set up to terminate the feedback loops if both of the following criteria are met:

  1. Change in total AM and PM VMT of two successive feedback loops is less than five percent
  2. The AM and PM volumes of more than 95 percent of freeway and arterial links change less than five percent in two successive loops.

The net effect of these changes are that the model runs one feedback loop less than the original model for the 2010 baseline scenario.

Highway Traffic Assignment

The model is able to run midday and nighttime highway assignments in parallel. The user can assign computer logical processors to time periods by filling the corresponding keys added to the user interface. Figure 7-1, below, shows an example of the Cube catalog (last page of user interface page) for a computer with 8 logical processors. The AM and the PM assignments use all available logical processors, whereas the midday and nighttime assignments use different logical processors and can therefore run in parallel.

The model currently runs AM and PM assignments in sequence; however, it will be able to run them in parallel with minor changes in the model. In this case, the model should know which computer logical processor is the first one used for AM assignment (also which one is the first one for PM period). The interface has these two keys now and, since they are not run in parallel, the value for them should be higher than number of computer logical processors. The default value, therefore, was set to 25, which is suitable for any machine with up to 24 logical processors.

Figure 7-1: Assigning computer logical processors to highway assignments by time period

Highway Traffic Assignment Parameters

The assignment convergence criterion was changed to the accepted standard practice of relative gap. In addition, the maximum number of iterations was increased from 50 to 150, allowing for greater accuracy in the assignment process. The model is setup to use a tighter relative gap in the highway assignment after the first loop. Following best practice recommendations for regional highway assignments, it is recommended that this relative gap be set to 0.0001. The user may increase or decrease the relative gap, depending on the accuracy level required for the analysis under consideration. Figure 7-2 shows that the relative gap used after the first feedback loop was added to the interface as a key controlled by the user.

Figure 7-2: Setting the relative gap used in highway assignment after the second feedback loop

Post-Process Analysis

The Select link analysis is set to run after the feedback loop. The user selects the option to run a selected link analysis on typically the third page of the user interface, as shown in Figure 7-3. The select link analysis can be run for any of the time periods, including the daily assignment, by selecting the specific option. In order to run the daily select link option, all the time periods need to be run for the select link.

If the user wants to save the congested path files, they can choose the option to save the path file for a particular period. The paths are saved in an extra highway assignment run at the end of the model based on the final congested network. It should be noted that Cube Cluster does not support the use of multiple logical processors for path saving; therefore, this step takes a bit longer than would a normal assignment that can be distributed across processors.

Figure 7-3: Keys used to define links for select link analysis and time periods for path saving

Table 7-1 lists all the fields in the loaded network files. The two columns on the right lists the fields associated with the links which the user selected in the "select link" option shown in Figure 7-3. The yellow rows on the table are used in the calculation listed on the last row of the table and calculates the total link volume.  

Table 7-1 NERPAB1v2 Loaded highway network fields 

NERPM AB LOADED NETWORK FieldsNERPM AB LOADED NETWORK Fields
New VariableDescriptionNew VariableDescription
COUNTDirectional 2010 AADT   count value, 0 if not available  
AMCOUNTDirectional 2010 AM   count value, 0 if not available  
MDCOUNTDirectional 2010 MD   count value, 0 if not available  
PMCOUNTDirectional 2010 PM   count value, 0 if not available  
NTCOUNTDirectional 2010 NT   count value, 0 if not available  
SCREENLINE_YR10Screenline number for   year 2010  
NT_VL_TOT_10ANight offpeak time   total volume for year 2010 and scenario "A"NTSL_VL_TOT_10ASelected Link Night   offpeak time total volume for year 2010 and scenario "A"
NT_VL_DA_10ANight offpeak   DA-Free&Toll-II&IE+EE trafficNTSL_VL_DA_10ASelected Link Night   offpeak DA-Free&Toll-II&IE+EE traffic
NT_F_DA_10ANight offpeak   DA-II&IE-Free trafficNTSL_F_DA_10ASelected Link Night   offpeak DA-II&IE-Free traffic
NT_T_DA_10ANight offpeak   DA-II&IE-TollNTSL_T_DA_10ASelected Link Night   offpeak DA-II&IE-Toll
NT_F_EDA_10ANight offpeak   DA-EE-FreeNTSL_F_EDA_10ASelected Link Night   offpeak DA-EE-Free
NT_T_EDA_10ANight offpeak   DA-EE-TollNTSL_T_EDA_10ASelected Link Night   offpeak DA-EE-Toll
NT_VL_SR2_10ANight offpeak   SR2-Free&Toll-II&IE+EE trafficNTSL_VL_SR2_10ASelected Link Night   offpeak SR2-Free&Toll-II&IE+EE traffic
NT_F_SR2_10ANight offpeak   SR2-II&IE-FreeNTSL_F_SR2_10ASelected Link Night   offpeak SR2-II&IE-Free
NT_T_SR2_10ANight offpeak   SR2-II&IE-TollNTSL_T_SR2_10ASelected Link Night   offpeak SR2-II&IE-Toll
NT_F_ESR2_10ANight offpeak   SR2-EE-FreeNTSL_F_ESR2_10ASelected Link Night   offpeak SR2-EE-Free
NT_T_ESR2_10ANight offpeak   SR2-EE-TollNTSL_T_ESR2_10ASelected Link Night   offpeak SR2-EE-Toll
NT_VL_SR3_10ANight offpeak   SR3-Free&Toll-II&IE+EE trafficNTSL_VL_SR3_10ASelected Link Night   offpeak SR3-Free&Toll-II&IE+EE traffic
NT_F_SR3_10ANight offpeak   SR3-II&IE-FreeNTSL_F_SR3_10ASelected Link Night   offpeak SR3-II&IE-Free
NT_T_SR3_10ANight offpeak   SR3-II&IE-TollNTSL_T_SR3_10ASelected Link Night   offpeak SR3-II&IE-Toll
NT_F_ESR3_10ANight offpeak   SR3-EE-FreeNTSL_F_ESR3_10ASelected Link Night   offpeak SR3-EE-Free
NT_T_ESR3_10ANight offpeak   SR3-EE-TollNTSL_T_ESR3_10ASelected Link Night   offpeak SR3-EE-Toll
NT_VL_TRK_10ANight offpeak   Truck-II&IE+EE+PortNTSL_VL_TRK_10ASelected Link Night   offpeak Truck-II&IE+EE+Port
NT_VL_PRTTK_10ANight offpeak   Port-TruckNTSL_VL_PRTTK_10ASelected Link Night   offpeak Port-Truck
NT_VL_EXT_10ANight offpeak EXT-TRK   + EE-Free&Toll(DA+SR2+SR3)NTSL_VL_EXT_10ASelected Link Night   offpeak EXT-TRK + EE-Free&Toll(DA+SR2+SR3)
NT_VC_10ANight offpeak V/C   Ratio  
NT_CGSPEED_10ANight offpeak average   congested speed  
NT_VMT_10ANight offpeak VMT  
NT_VHT_10ANight offpeak VHT  
NT_CGTIME_10ANight offpeak   congested travel time  
NT_FLGCGSPDZERONight offpeak   congested speed is 0 indicator, 1 if speed is 0  
NT_VCCAPRTO_10ANight offpeak V/C   Ratio (same as VC_10A)  
PM_VL_TOT_10APM peak time total   volume for year 2010 and scenario "A"PMSL_VL_TOT_10ASelected Link PM peak   time total volume for year 2010 and scenario "A"
PM_VL_DA_10APM peak   DA-Free&Toll-II&IE+EE trafficPMSL_VL_DA_10ASelected Link PM peak   DA-Free&Toll-II&IE+EE traffic
PM_F_DA_10APM peak   DA-II&IE-Free trafficPMSL_F_DA_10ASelected Link PM peak   DA-II&IE-Free traffic
PM_T_DA_10APM peak   DA-II&IE-TollPMSL_T_DA_10ASelected Link PM peak   DA-II&IE-Toll
PM_F_EDA_10APM peak DA-EE-FreePMSL_F_EDA_10ASelected Link PM peak   DA-EE-Free
PM_T_EDA_10APM peak DA-EE-TollPMSL_T_EDA_10ASelected Link PM peak   DA-EE-Toll
PM_VL_SR2_10APM peak   SR2-Free&Toll-II&IE+EE trafficPMSL_VL_SR2_10ASelected Link PM peak   SR2-Free&Toll-II&IE+EE traffic
PM_F_SR2_10APM peak   SR2-II&IE-FreePMSL_F_SR2_10ASelected Link PM peak   SR2-II&IE-Free
PM_T_SR2_10APM peak   SR2-II&IE-TollPMSL_T_SR2_10ASelected Link PM peak   SR2-II&IE-Toll
PM_F_ESR2_10APM peak SR2-EE-FreePMSL_F_ESR2_10ASelected Link PM peak   SR2-EE-Free
PM_T_ESR2_10APM peak SR2-EE-TollPMSL_T_ESR2_10ASelected Link PM peak   SR2-EE-Toll
PM_VL_SR3_10APM peak   SR3-Free&Toll-II&IE+EE trafficPMSL_VL_SR3_10ASelected Link PM peak   SR3-Free&Toll-II&IE+EE traffic
PM_F_SR3_10APM peak   SR3-II&IE-FreePMSL_F_SR3_10ASelected Link PM peak   SR3-II&IE-Free
PM_T_SR3_10APM peak   SR3-II&IE-TollPMSL_T_SR3_10ASelected Link PM peak   SR3-II&IE-Toll
PM_F_ESR3_10APM peak SR3-EE-FreePMSL_F_ESR3_10ASelected Link PM peak   SR3-EE-Free
PM_T_ESR3_10APM peak SR3-EE-TollPMSL_T_ESR3_10ASelected Link PM peak   SR3-EE-Toll
PM_VL_TRK_10APM peak   Truck-II&IE+EE+PortPMSL_VL_TRK_10ASelected Link PM peak   Truck-II&IE+EE+Port
PM_VL_PRTTK_10APM peak Port-TruckPMSL_VL_PRTTK_10ASelected Link PM peak   Port-Truck
PM_VL_EXT_10APM peak EXT-TRK +   EE-Free&Toll(DA+SR2+SR3)PMSL_VL_EXT_10ASelected Link PM peak   EXT-TRK + EE-Free&Toll(DA+SR2+SR3)
PM_VC_10APM peak V/C Ratio  
PM_CGSPEED_10APM peak average   congested speed  
PM_VMT_10APM peak VMT  
PM_VHT_10APM peak VHT  
PM_CGTIME_10APM peak congested   travel time  
PM_FLGCGSPDZEROPM peak congested   speed is 0 indicator, 1 if speed is 0  
PM_VCCAPRTO_10APM peak V/C Ratio   (same as VC_10A)  
MD_VL_TOT_10AMD offpeak time total   volume for year 2010 and scenario "A"MDSL_VL_TOT_10ASelected Link MD   offpeak time total volume for year 2010 and scenario "A"
MD_VL_DA_10AMD offpeak   DA-Free&Toll-II&IE+EE trafficMDSL_VL_DA_10ASelected Link MD   offpeak DA-Free&Toll-II&IE+EE traffic
MD_F_DA_10AMD offpeak   DA-II&IE-Free trafficMDSL_F_DA_10ASelected Link MD   offpeak DA-II&IE-Free traffic
MD_T_DA_10AMD offpeak   DA-II&IE-TollMDSL_T_DA_10ASelected Link MD   offpeak DA-II&IE-Toll
MD_F_EDA_10AMD offpeak DA-EE-FreeMDSL_F_EDA_10ASelected Link MD   offpeak DA-EE-Free
MD_T_EDA_10AMD offpeak DA-EE-TollMDSL_T_EDA_10ASelected Link MD   offpeak DA-EE-Toll
MD_VL_SR2_10AMD offpeak   SR2-Free&Toll-II&IE+EE trafficMDSL_VL_SR2_10ASelected Link MD   offpeak SR2-Free&Toll-II&IE+EE traffic
MD_F_SR2_10AMD offpeak   SR2-II&IE-FreeMDSL_F_SR2_10ASelected Link MD   offpeak SR2-II&IE-Free
MD_T_SR2_10AMD offpeak   SR2-II&IE-TollMDSL_T_SR2_10ASelected Link MD   offpeak SR2-II&IE-Toll
MD_F_ESR2_10AMD offpeak   SR2-EE-FreeMDSL_F_ESR2_10ASelected Link MD   offpeak SR2-EE-Free
MD_T_ESR2_10AMD offpeak   SR2-EE-TollMDSL_T_ESR2_10ASelected Link MD   offpeak SR2-EE-Toll
MD_VL_SR3_10AMD offpeak   SR3-Free&Toll-II&IE+EE trafficMDSL_VL_SR3_10ASelected Link MD   offpeak SR3-Free&Toll-II&IE+EE traffic
MD_F_SR3_10AMD offpeak   SR3-II&IE-FreeMDSL_F_SR3_10ASelected Link MD   offpeak SR3-II&IE-Free
MD_T_SR3_10AMD offpeak   SR3-II&IE-TollMDSL_T_SR3_10ASelected Link MD   offpeak SR3-II&IE-Toll
MD_F_ESR3_10AMD offpeak   SR3-EE-FreeMDSL_F_ESR3_10ASelected Link MD   offpeak SR3-EE-Free
MD_T_ESR3_10AMD offpeak   SR3-EE-TollMDSL_T_ESR3_10ASelected Link MD   offpeak SR3-EE-Toll
MD_VL_TRK_10AMD offpeak   Truck-II&IE+EE+PortMDSL_VL_TRK_10ASelected Link MD   offpeak Truck-II&IE+EE+Port
MD_VL_PRTTK_10AMD offpeak Port-TruckMDSL_VL_PRTTK_10ASelected Link MD   offpeak Port-Truck
MD_VL_EXT_10AMD offpeak EXT-TRK +   EE-Free&Toll(DA+SR2+SR3)MDSL_VL_EXT_10ASelected Link MD   offpeak EXT-TRK + EE-Free&Toll(DA+SR2+SR3)
MD_VC_10AMD offpeak V/C Ratio  
MD_CGSPEED_10AMD offpeak average   congested speed  
MD_VMT_10AMD offpeak VMT  
MD_VHT_10AMD offpeak VHT  
MD_CGTIME_10AMD offpeak congested   travel time  
MD_FLGCGSPDZEROMD offpeak congested   speed is 0 indicator, 1 if speed is 0  
MD_VCCAPRTO_10AMD offpeak V/C Ratio   (same as VC_10A)  
AM_VL_TOT_10AAM peak time total   volume for year 2010 and scenario "A"AMSL_VL_TOT_10ASelected Link AM peak   time total volume for year 2010 and scenario "A"
AM_VL_DA_10AAM peak   DA-Free&Toll-II&IE+EE trafficAMSL_VL_DA_10ASelected Link AM peak   DA-Free&Toll-II&IE+EE traffic
AM_F_DA_10AAM peak   DA-II&IE-Free trafficAMSL_F_DA_10ASelected Link AM peak   DA-II&IE-Free traffic
AM_T_DA_10AAM peak   DA-II&IE-TollAMSL_T_DA_10ASelected Link AM peak   DA-II&IE-Toll
AM_F_EDA_10AAM peak DA-EE-FreeAMSL_F_EDA_10ASelected Link AM peak   DA-EE-Free
AM_T_EDA_10AAM peak DA-EE-TollAMSL_T_EDA_10ASelected Link AM peak   DA-EE-Toll
AM_VL_SR2_10AAM peak   SR2-Free&Toll-II&IE+EE trafficAMSL_VL_SR2_10ASelected Link AM peak   SR2-Free&Toll-II&IE+EE traffic
AM_F_SR2_10AAM peak   SR2-II&IE-FreeAMSL_F_SR2_10ASelected Link AM peak   SR2-II&IE-Free
AM_T_SR2_10AAM peak   SR2-II&IE-TollAMSL_T_SR2_10ASelected Link AM peak   SR2-II&IE-Toll
AM_F_ESR2_10AAM peak SR2-EE-FreeAMSL_F_ESR2_10ASelected Link AM peak   SR2-EE-Free
AM_T_ESR2_10AAM peak SR2-EE-TollAMSL_T_ESR2_10ASelected Link AM peak   SR2-EE-Toll
AM_VL_SR3_10AAM peak   SR3-Free&Toll-II&IE+EE trafficAMSL_VL_SR3_10ASelected Link AM peak   SR3-Free&Toll-II&IE+EE traffic
AM_F_SR3_10AAM peak   SR3-II&IE-FreeAMSL_F_SR3_10ASelected Link AM peak   SR3-II&IE-Free
AM_T_SR3_10AAM peak   SR3-II&IE-TollAMSL_T_SR3_10ASelected Link AM peak   SR3-II&IE-Toll
AM_F_ESR3_10AAM peak SR3-EE-FreeAMSL_F_ESR3_10ASelected Link AM peak   SR3-EE-Free
AM_T_ESR3_10AAM peak SR3-EE-TollAMSL_T_ESR3_10ASelected Link AM peak   SR3-EE-Toll
AM_VL_TRK_10AAM peak   Truck-II&IE+EE+PortAMSL_VL_TRK_10ASelected Link AM peak   Truck-II&IE+EE+Port
AM_VL_PRTTK_10AAM peak Port-TruckAMSL_VL_PRTTK_10ASelected Link AM peak   Port-Truck
AM_VL_EXT_10AAM peak EXT-TRK +   EE-Free&Toll(DA+SR2+SR3)AMSL_VL_EXT_10ASelected Link AM peak   EXT-TRK + EE-Free&Toll(DA+SR2+SR3)
AM_VC_10AAM peak V/C Ratio  
AM_CGSPEED_10AAM peak average   congested speed  
AM_VMT_10AAM peak VMT  
AM_VHT_10AAM peak VHT  
AM_CGTIME_10AAM peak congested   travel time  
AM_FLGCGSPDZEROAM peak congested   speed is 0 indicator, 1 if speed is 0  
AM_VCCAPRTO_10AAM peak V/C Ratio   (same as VC_10A)  
AL_VL_TOT_1ADaily time total   volume for year 2010 and scenario "A"ALSLSL_VL_TOT_1ASelected Link Daily   time total volume for year 2010 and scenario "A"
AL_VL_DA_10ADaily   DA-Free&Toll-II&IE+EE trafficALSL_VL_DA_10ASelected Link Daily   DA-Free&Toll-II&IE+EE traffic
AL_F_DA_10ADaily   DA-II&IE-Free trafficALSL_F_DA_10ASelected Link Daily   DA-II&IE-Free traffic
AL_T_DA_10ADaily   DA-II&IE-TollALSL_T_DA_10ASelected Link Daily   DA-II&IE-Toll
AL_F_EDA_10ADaily DA-EE-FreeALSL_F_EDA_10ASelected Link Daily   DA-EE-Free
AL_T_EDA_10ADaily DA-EE-TollALSL_T_EDA_10ASelected Link Daily   DA-EE-Toll
AL_VL_SR2_10ADaily   SR2-Free&Toll-II&IE+EE trafficALSL_VL_SR2_10ASelected Link Daily   SR2-Free&Toll-II&IE+EE traffic
AL_F_SR2_10ADaily   SR2-II&IE-FreeALSL_F_SR2_10ASelected Link Daily   SR2-II&IE-Free
AL_T_SR2_10A.Daily   SR2-II&IE-TollALSL_T_SR2_10A.Selected Link Daily   SR2-II&IE-Toll
AL_F_ESR2_10ADaily SR2-EE-FreeALSL_F_ESR2_10ASelected Link Daily   SR2-EE-Free
AL_T_ESR2_10ADaily SR2-EE-TollALSL_T_ESR2_10ASelected Link Daily   SR2-EE-Toll
AL_VL_SR3_10ADaily   SR3-Free&Toll-II&IE+EE trafficALSL_VL_SR3_10ASelected Link Daily   SR3-Free&Toll-II&IE+EE traffic
AL_F_SR3_10ADaily   SR3-II&IE-FreeALSL_F_SR3_10ASelected Link Daily   SR3-II&IE-Free
AL_T_SR3_10ADaily   SR3-II&IE-TollALSL_T_SR3_10ASelected Link Daily   SR3-II&IE-Toll
AL_F_ESR3_10ADaily SR3-EE-FreeALSL_F_ESR3_10ASelected Link Daily   SR3-EE-Free
AL_T_ESR3_10ADaily SR3-EE-TollALSL_T_ESR3_10ASelected Link Daily   SR3-EE-Toll
AL_VL_TRK_10ADaily   Truck-II&IE+EE+PortALSL_VL_TRK_10ASelected Link Daily   Truck-II&IE+EE+Port
AL_VL_PRTTK_10ADaily Port-TruckALSL_VL_PRTTK_10ASelected Link Daily   Port-Truck
AL_VL_EXT_10ADaily EXT-TRK +   EE-Free&Toll(DA+SR2+SR3)ALSL_VL_EXT_10ASelected Link Daily   EXT-TRK + EE-Free&Toll(DA+SR2+SR3)
AL_VMT_10ADaily VMT  
AL_VHT_10ADaily VHT  
AL_CGTIME_10ADaily congested   travel time, weighted average of four time period  
AL_CGSPEED_10ADaily congested   travel speed  
AL_VOLCNTRTOOld measure   (obsolete)  
AL_VCCAPRTO_10ADaily V/C Ratio  
TOTAL_VOLUMEAL_VL_TOT_1A+AL_VL_TOT_1A.R  

 

Redundant Steps

Several steps in the trip distribution part of the model are no longer needed.

Model operations previously used to combine trip tables are no longer necessary because DaySim uses its own set of procedures for creating trip tables from trip lists.

The pre-assignment step is now run only once, during the first feedback loop iteration. This is because the outputs from pre-assignment are used to build the transit network, which is only run during the first feedback  loop iteration.

Clean up Cube Catalog Interface

The validation base year key (Valyear) is not read by the model and was removed from the catalog interface. All other keys in the interface are needed.

Performance Improvements

Table 7-2 shows the run times based on a 2015 vintage workstation with 8 logical processors before the changes were made and the run times after the changes, with various settings. Comparing the rows shaded in orange, the changes made to the model decreased the run time by more than 9 hours, a 44 percent improvement, for the base year model (2010), using the stricter relative gap and without path saving and select link analysis. The run of the same model with select link analysis for AM and PM periods and saving path file for AM period ran for 16:27, using the stricter relative gap, which is reasonable.

Table 7-2: Run time of the original and improved (V2) NERPMAB1v2 models Using a workstation with 8 logical processors

 

New and Updated Scripts

Several new scripts were created and/or updated to support the listed changes. Table 7-3 shows the four scripts that are updated in the NERPMAB1v2 model, all corresponding to the highway assignments by time period. Table 7-4 presents the new scripts in the NERPMAB1v2 model with a brief description for each.

Table 7-3: Updated Scripts in the NERPMAB1v2 model

Table 7-4: New scripts in the NERPMAB1v2 model