Trip Generation Models in TransCAD Murtaza Haider [email protected] Tel: 416.979.5000, ext. 2480 Outline • TransCAD’s use for – Basic tabulations – Statistical analysis – Trip generation models Tabulations and Statistics • Goal: understand TransCAD’s statistical analysis tools and how you can use them to: – Generate summary statistics – Perform tabulations and cross-tabulations – Determine correlations between variables – Create, estimate and evaluate linear regression and binary logit models – Calculate spatial autocorrelation Basics: Statistics • Definition: A branch of mathematics dealing with the collection, analysis, interpretation and presentation of masses of numerical data. In TransCAD, a range of statistical methods are available. Basics: Tabulation • Definition: A classification of records or features in a layer based on the values for either one or two data fields. Example: One-Way Tabulation Example: Two-Way Tabulations Quick Start: Calculating Summary Statistics • Choose File-Close All, then choose File-Open or click on the toolbar. • Open the DBASE file CUSTOMER.DBF in the TCW\TUTORIAL directory. TransCAD opens a customer sales database. • Choose Dataview-Statistics. TransCAD calculates the summary statistics for the dataview. Getting Ready for a One-Way Tabulation • Choose File-Close All, then choose File-Open or click on the toolbar. • Open the DBASE file BUS_SURV.DBF in the TCW\EXERCISE directory. TransCAD displays a survey taken from transit riders. • Choose Statistics-Tabulations. TransCAD displays the Tabulations dialog box. • Choose AGE in the Field 1 drop-down list. Performing a One-Way Tabulation • All the other settings are correct. Click OK. • Enter MYTAB as the output filename and click OK. TransCAD creates a tabulation on the AGE field and displays a matrix containing the age distribution. • Make the BUS_SURV dataview the active window. • Choose Statistics-Tabulations again. Performing a Two-Way Tabulation • For HH_SIZE from the Field 1 drop-down list and AUTOS from the Field 2 drop-down list. • Choose List of Values from both Methods dropdown lists, and 5 from both # Classes drop-down lists. • Enter MYTAB2 as the output filename and click OK. TransCAD produces a two-way tabulation of AUTOS and HH_SIZE. In Depth: Tabulations • Choose Statistics-Tabulations to display the Tabulations dialog box: Basics: Correlation • Definition: A calculated statistic that determines the interdependence between mathematical variables. The calculated correlation can range from 1 (perfectly positively correlated) through 0 (no correlation) to -1 (perfectly negatively correlated) Example: Correlation Positive Correlation Negative Correlation No Correlation Getting Ready to Calculate Correlations • Choose File-Close All, then choose File-Open or click on the toolbar. • Open the DBASE file BUS_SURV.DBF in TCW\EXERCISE. TransCAD displays a survey taken from transit riders. • Choose Statistics-Correlations to display the Correlations dialog box. Calculating Correlations • Choose AGE, AUTOS, HHINC1000S and EDUCATION from the Fields drop-down list (using the Ctrl key) and click OK. • Enter MYCORREL as the filename and click OK. TransCAD calculates the correlations among the selected variables and puts the results in a matrix. TransCAD also launches Notepad to display a report file. Close Notepad after reading the report. Exercise #1 • Open any table that has two or more numerical fields and perform both one- and two-way tabulations on the data fields. Experiment with changing the methods and the number of classes to see the effects on the ranges. Exercise #2 • Using the same table used in Exercise #1, calculate the correlations of all the fields in the table. Analyze the results and see which fields are positively or negatively correlated with each other. Statistical Modeling • TransCAD provides various tools for statistical modeling. You can: – Estimate a linear regression model – Evaluate a linear regression model – Create a linear regression model – Estimate, evaluate and create binary logit models Basics: Linear Regression • Definition: A derived linear relationship between two or more related variables used to predict values of one variable when given the values of other variables Example: Linear Regression Variable Y Y = aX + b Variable X Getting Ready to Estimate a Regression Model • Choose File-Close All, then choose File-Open or click on the toolbar. • Open the DBASE file FL_BSURV.DBF in TCW\EXERCISE. TransCAD displays a survey taken from transit riders. • Choose Statistics-Model Estimation. • Choose HHINC1000S from the Dependent dropdown list. Estimating a Linear Regression Model • Choose AGE, AUTOS and EDUCATION from the Independent drop-down list, and click OK. • Enter MYEST as the output filename and click OK. TransCAD creates a model file and reports the results of the estimation. Close Notepad after reading the report. • Make the FL_BSURV dataview the active window. Creating a Model File • Choose File-Save As, choose dBASE file from the List Files of Type drop-down list and enter MYSURV as the output filename. • Open the DBASE file MYSURV.DBF. • Choose Statistics-Create Model File. • Choose AGE, AUTOS, and EDUCATION as the model variables and click OK. Getting Ready to Apply a Model • Enter 1 for the Coefficient for CONSTANT and 0.5 for the Coefficient for AUTOS. • All the other settings are correct. Click OK. • Enter MYMOD as the model filename and click OK. TransCAD creates the model file. • Choose Statistics-Model Evaluation. • Choose MYMOD.MOD for the model file and click OK. Applying a Model • Choose HHINC1000S from the Results In dropdown list and click OK. TransCAD evaluates the model and estimates the values for HHINC1000S. • TransCAD also launches Notepad to display a report file. Close Notepad after reading the report. In Depth: Statistical Modeling • The .MOD model files created from TransCAD are text files and can be edited. • You can also: – Create formula fields before estimating or applying models to create transformations – Estimate and evaluate models based on selections of records – Estimate binary logit models Model Files Model of HHINC1000S for BUS_SURV (All Records) "CONSTANT",33.3981655761 "AGE",-0.06061504867868 "AUTOS",2.14894268478 "EDUCATION",-0.04778903526361 Estimating a Model • Choose Statistics-Model Estimation to display the Model Estimation dialog box: Evaluating a Model • Choose Statistics-Model Evaluation to display the Forecast dialog box: Creating a Model • Choose Statistics-Create Model File to display the Model Coefficients dialog box: Exercise #1 • Open any table that has two or more numerical fields and estimate a linear regression model using any fields that interest you. Analyze the results and look at the R-squared and t-statistics to see if your model is valid. Exercise #2 • Open any table with two or more numerical fields and copy it to another table. Using the copied table, create a model file. Using your model file, apply your model to forecast your dependent values. Basics: Spatial Autocorrelation • Definition: A statistic that determines whether adjacent observations in a geographic area sample have a tendency to have correlated values. Basics: Adjacency Matrix • Definition: A matrix that contains one row and one column for each area feature. • The Adjacency Matrix indicates whether a pair of areas have a common border • The Adjacency Level Matrix indicates the level of adjacency, from 0 to 1 • The Common Border Length Matrix gives the length of the common border Example: Adjacency Matrix Getting Ready for Spatial Autocorrelation • Choose File-Close All, then choose File-Open or click on the toolbar. • Open the geographic file UTOWN_ZN.DBD in TCW\TUTORIAL. TransCAD displays the zones for UTOWN. • Choose Statistics-Adjacency Matrix to display the Adjacency Matrix dialog box. Calculating Spatial Adjacency • All the settings are correct. Click OK. • Enter MYADJ as the matrix filename and click OK. TransCAD creates an adjacency matrix for the area layer. • TransCAD also launches Notepad to display a report file. Close Notepad after reading the report. Calculating Spatial Autocorrelation #1 • Make the Zone map the active window. • Choose Statistics-Spatial Autocorrelation to display the Spatial Autocorrelation dialog box. • Choose [TOTAL HH] from the Data Field dropdown list. Calculating Spatial Autocorrelation #2 • Click OK. TransCAD calculates the spatial autocorrelation of the [TOTAL HH] field of the area layer • TransCAD also launches Notepad to display a report file. Close Notepad after reading the report. Trip Generation Procedures • Goal: understand how to use TransCAD to: – Generate inputs for trip generation – Run the trip generation procedures – Understand, interpret and analyze procedure results Trip Generation • Used to predict trips generated by households or zones given data about “trip generators” in the zone • Trip ends are classified as productions and attractions or origins and destinations • Separate models are usually used to estimate each trip end • Final results are balanced produced and attracted trips for each zone in the analysis area for each trip purpose Required Inputs for Trip Generation • Data table containing, for each zone, fields for “trip generators” (e.g., households, vehicles, employment) • Model for each trip purpose used • Trip rate data in model file or table form (e.g., 2 trips per 1 vehicle household) for each trip purpose Linear Regression • Simplified generation models consist of regressions that estimate generated trips • Often, produced or attracted trips are predicted given other explanatory variables, such as households, # of vehicles, employment, etc. • Data sets for regression can be aggregated (at the zone level) or disaggregate (individual) and then aggregated to the zone Estimating a Regression Model • Choose File-Close All, then choose File-Open or click on the toolbar. – Open the map file EL_PASO.MAP in TCW\TUTORIAL. – Choose Statistics-Model Estimation. – Click the Regression radio button – Choose [VEH WORK TRIPS] from the scroll list – Choose the following from the Independent TAB • RETAIL EMP • NON RETAIL EMP – Click OK – Type “Myattr1” as the file name and Click SAVE Regression Results Field Name [RETAIL EMP] [NON RETAIL EMP] [VEH WORK TRIPS] Mean Std Dev 49.637 93.8337 324.836 632.875 691.548 1315.48 Dependent field is [VEH WORK TRIPS] Source Model Error Total R Squared Adj R Squared Field Name CONSTANT [RETAIL EMP] [NON RETAIL EMP] df SS 2 559 561 Mean SS F Ratio 9.65E+08 4.83E+08 50239.7 5.37E+06 9608.22 9.71E+08 0.9945 0.9944 Estimate Std. Error t stat -9.08349 2.2242 0.0655268 33.9433 1.817 0.00971539 187.023 Estimating Trip Generation in TransCAD • Save the downloaded data file as *.DBF • Open the file in TransCAD • Estimate models for work and non-work trips Data Description • zone - Zone ID • nstud - Students in Hhld • dwtype - Dwelling Type • nfem - Females in Hhhld • npers - Persons in Hhld • nmale - Males in Hhld • nveh - Vehicles in Hhld • nchild - Children in Hhld • nlic - Licensed Persons in hhld • n65+ - Seniors in Hhld • nftw - Full-time workers • nnwk - Non-work trips • nptw - Part-time workers • expfac - Expansion Factor • nwah - Workers at home • nwork - Work Trips Creating a Model File • Choose File-Save As, choose dBASE file from the List Files of Type drop-down list and enter MYSURV as the output filename. • Open the dBASE file MYSURV.DBF. • Choose Statistics-Create Model File. • Choose AGE, AUTOS, and EDUCATION as the model variables and click OK. Getting Ready to Apply a Model • Enter 1 for the Coefficient for CONSTANT and 0.5 for the Coefficient for AUTOS. • All the other settings are correct. Click OK. • Enter MYMOD as the model filename and click OK. TransCAD creates the model file. • Choose Statistics-Model Evaluation. • Choose MYMOD.MOD for the model file and click OK. Applying a Model • Choose HHINC1000S from the Results In dropdown list and click OK. TransCAD evaluates the model and estimates the values for HHINC1000S. • TransCAD also launches Notepad to display a report file. Close Notepad after reading the report. In Depth: Statistical Modeling • The .MOD model files created from TransCAD are text files and can be edited. • You can also: – Create formula fields before estimating or applying models for transformations – Estimate and evaluate models based on selections of records – Estimate binary logit models Model Files Model of HHINC1000S for BUS_SURV (All Records) "CONSTANT",33.3981655761 "AGE",-0.06061504867868 "AUTOS",2.14894268478 "EDUCATION",-0.04778903526361 Cross Classification • Cross Classification methods separate the population into homogeneous groups based on certain socio-economic characteristics • Average trip rates are estimated for each classified group, the rate depending on a zone statistic (e.g., trips/household) • Once a zone or subset of a zone is classified into a group, the zone statistic is multiplied by the appropriate trip rate to estimate the total trips generated Inputs for Cross Classification • Trip rate table – Defines, for each trip purpose, the classifications used and the trip rates for each classification • Zone data table – Contains information on the average values of the classification fields within each zone Example: Trip Rate Table Example: Zone Data Table Getting Ready to Run Cross Classification • Choose File-Close All, then choose File-Open or click on the toolbar. • Open the workspace VERMONT.WRK in TCW\TUTORIAL. • Choose Planning>Trip Productions>Cross Classification. • Choose MCD from the Zone Data drop-down list. • Choose Households from the Zone or Subzone drop-down list. Setting Up Cross Classification • Choose VMT_CRCL from the Trip Rate Table drop-down list. • Choose all three trip purposes. • Choose [Avg Car/HH] from the Rate Table Fields scroll list. • Choose [AUTO/HH] from the Zone Data Field drop-down list. Running Cross Classification • Choose [Avg Inc/HH] from the Rate Table Fields scroll list. • Choose [INC/HH] from the Zone Data Field dropdown list. • The settings are all correct. Click OK. • Enter MYPROD1 as the filename and click OK. TransCAD computes the productions for all zones and purposes and displays a dataview of the results. Sub-Groups Within Zones • In some cross classification models, zone data are divided into several homogeneous groups and different trip rates are applied to each homogenous group • The estimated trips for each sub-group are then summed to predict total trips generated for the zone • TransCAD’s cross classification procedure can accomodate these types of models Cross Classification With Sub-Groups Zonal Data With Sub-Groups Trip Rate Table Cross-Classification Building Cross Classification Tables • TransCAD provides a procedure to create a trip rate table given disaggregate data (go to Planning>Planning utilities>Build crossclassification table) • The user supplies the data, the classification fields and the classification ranges and the procedure calculates average trip rates and variances for the ranges • In defining classification fields and ranges, it is good practice to have homogeneity within ranges and heterogeneity between ranges Example: Creating Trip Rate Tables Quick Response Models • TransCAD provides procedures to estimate productions and attractions using the default trip rate table from NCHRP 187 and the Quick Response Method • QRM procedures estimate trips given number of households per zone and, optionally data on income, autos, employment, etc. • This trip rate table is based on data collected from across the United States Estimating Trips Productions Using QRM • Choose File-Close All, then choose File-Open or click on the toolbar. • Open the map UTOWN.MAP from TCW\TUTORIAL. • Choose Planning-Trip Production-Quick Response. • Enter 100 as the Urban Area Population. • Choose Autos/HH from the Classify By drop-down list. Estimating Trips • Choose [Autos/HH] from the Auto/HH drop-down list. • All other settings are correct. Click OK. • Enter MYPROD3 as the output file and click OK. TransCAD calculates the trip productions and displays them in a dataview. Balancing • Usually, separate models are used to estimate productions and attractions, which often leads to a discrepancy between total trips produced and total trips attracted. • TransCAD provides several balancing methods to create production and attraction estimates which sum up to the same number of trips for each purpose Balancing Methods • Hold productions constant • Hold attractions constant • Weighted sum of productions and attractions • Sum to user specified value Quick Start: Getting Ready to Balance • Choose File-Close All, then choose File-Open or click on the toolbar. • Open the map file VMT_BAL.MAP in TCW\TUTORIAL. • Choose Planning-Balance. • Choose [HBW-P] from the drop-down list directly under Vector 1. • Click the Add button. Balancing Productions and Attractions • Choose [HBNW-P] from the drop-down list directly under Vector 1. • Choose Sum to Value from the Method drop-down list. • Enter 1000000 as the value to sum to and click OK. • Enter MYBAL as the output file name and click OK. TransCAD balances the two sets of vectors. In Depth: Balancing Options Productions, Attractions and Balancing w/ QRM

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