The accessibility calculator computes for each LUZ pair the logsum-based accessibilities for 2 time-of-day periods (off-peak, peak), 4 income categories (low, medium, high, very high), and 3 auto sufficiency categories (zero autos, number of autos greater than number of workers, number of autos less than or equal to number of workers). Thus, a total of 24 origin-based accessibilities are produced for each LUZ.
The accessibility calculator is included in the ARC CT-RAMP Java archive file, arc.jar. It is currently set up to run on a single machine using 8 threads but can be configured to utilize additional computational resources through the “accessibility.properties” file under the project directory.
To run the calculator:
Table 11-1 lists the files required to run the accessibility calculator. All the input .csv and .xls files are specified through accessibility.properties.
Table 11-1 Files Needed to Run the Accessibility Calculator
| File Name and Path (in relation to project directory | Description |
|---|---|
| accessibilities.properties | File containing property settings for the accessibility calculator |
| accessibility.csv | TAZ-level accessibilities computed by main model script |
| zoneData.csv | TAZ-level zonal data produced by main model script |
| ctrampModels/geographicCwalk.csv | TAZ to LUZ lookup table |
| ctrampModels/accessibility_utility_constants.xls | Constants to be added to the utility calculation for different auto sufficiency levels, modes, and purposes |
| ctrampModels/accessibility_utility.xls | Mode choice utility equations for calculating logsums |
| ctrampModels/mandatory_accessibility_alts.csv | Accessibilities defined for mandatory purpose |
| ctrampModels/nonMandatory_accessibility_alts.csv | Accessibilities defined for non-mandatory purpose |
| Skims for AM, PM and MD periods | Skims computed by main model script |
The calculator produces 24 output files, one for each combination of time-of-day periods, income category, and auto sufficiency category. Table 11-2 lists the names of the accessibility 24 files and Table 11-3 describes the fields in each of these files. The calculator also produces a column-wise merge of all 24 accessibilities in “all_accessibilities.csv”. All output files are written to the “accessibility” sub-directory under the project folder.
Table 11-2 Accessibility Files Produced by the Accessibility Calculator
| Time Period | Output Files |
|---|---|
| Off-peak Period | Op_lowInc_0_autos |
| Op_medInc_0_autos | |
| Op_highInc_0_autos | |
| Op_veryHighInc_0_autos | |
| Op_lowInc_autos_lt_workers | |
| Op_medInc_autos_lt_workers | |
| Op_highInc_autos_lt_workers | |
| Op_veryHighInc_autos_lt_workers | |
| Op_lowInc_autos_ge_workers | |
| Op_medInc_autos_ge_workers | |
| Op_highInc_autos_ge_workers | |
| Op_veryHighInc_autos_ge_workers | |
| Peak Period | Pk_lowInc_0_autos |
| Pk_medInc_0_autos | |
| Pk_highInc_0_autos | |
| Pk_veryHighInc_0_autos | |
| Pk_lowInc_autos_lt_workers | |
| Pk_medInc_autos_lt_workers | |
| Pk_highInc_autos_lt_workers | |
| Pk_veryHighInc_autos_lt_workers | |
| Pk_lowInc_autos_ge_workers | |
| Pk_medInc_autos_ge_workers | |
| Pk_highInc_autos_ge_workers | |
| Pk_veryHighInc_autos_ge_workers |
Table 11-3 Content of Accessibility Files
| Field | Description |
|---|---|
| origLUZ | Origin LUZ |
| destLUZ | Destination LUZ |
| accessibility | Accessibility between origLUZ and destLUZ |
| zone_pairs | Number of TAZ pairs nested within the LUZ pair |