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Surface Transportation Efficiency Analysis Model (STEAM)User Manual

3.0  Input and Output Files

This chapter describes the concept of "market sectors", the basic organizing principle of a STEAM 2.0 analysis. The chapter also describes the inputs necessary for the analysis and the output files produced by STEAM 2.0.


3.1 Explanation of Market Sectors

In conducting a STEAM 2.0 analysis, the software user first divides travel demand into a set of "market sectors". Market sectors describe a specific transportation user segment with unique travel characteristics. Most often, market sectors correspond to specific trip purposes served by particular modes of travel. However, STEAM 2.0 sets no limits on how markets sectors are defined. Unique market sectors can be defined for different trip purposes, geographic submarkets, or time periods. Bus work trips during the off-peak period is an example of a market sector. More aggregate definitions of a market sector can also be used; e.g., all weekday express bus riders.

For each market sector to be analyzed, the STEAM 2.0 user must provide a Base Case and an Improvement Case trip table.1 If an analysis of benefits to resident trip-makers is desired, a table of trips in P/A format must be provided. The availability of trip tables from the four-step planning process will usually dictate the set of market sectors to be analyzed by STEAM 2.0.

In estimating user benefits, STEAM 2.0 compares travel times and costs under the Base and Improvement Cases for trips from each zone to each other zone. Only zone pairs for which travel times can be determined are included in this calculation. For highway modes (automobile, truck, carpool), STEAM 2.0 includes a network analysis module that can be used to calculate zone-to-zone travel times using special speed-volume relationships developed for STEAM 2.0. Alternatively, the STEAM 2.0 user may wish to provide his or her own matrix of zone to zone travel times and bypass the network analysis module in STEAM 2.0 (if the user provides his own zone-to-zone travel times the user must calculate any external costs and enter them in the non-mileage based external cost variables). For transit modes (local bus, express bus, light rail, and heavy rail), STEAM 2.0 does not have a network analysis capability, so it is assumed the STEAM 2.0 user will provide Base and Improvement Case matrices of zone-to-zone travel times for these modes. For both highway and transit modes, the STEAM 2.0 user can also provide Base and Improvement Case matrices of out-of-vehicle (walk, wait) times and out-of-pocket costs (e.g., fares, tolls).

The following exhibit presents a graphic layout of the input files associated with a market sector. As shown in the exhibit, the files are grouped into a "Base Case" and an "Improvement Case" representing conditions before and after the proposed investment.

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3.2 Input Files

There are several input files required for a STEAM 2.0 analysis. These include:

The input files are described below:

Network Input File - Contains the road network information that is used in the network analysis module to calculate the minimum travel times and distances for each zone to zone pair. A base and improvement case network file are required for market sectors for which a network analysis is performed.

Network Output File - STEAM 2.0 model stores the minimum travel times and distances for a given network in this file. This information is used later in the benefit-cost estimation. A base and improvement case network output file are necessary for market sectors for which a network analysis is performed.

Zone Information File - Contains zonal-level information needed for the travel time and accessibility analysis and for the aggregation of user benefits by user-defined districts. Each zone number is identified with the corresponding centroid number, and, optionally, its district affiliation, population and employment. Only one centroid file is necessary. This file is used in both the base and improvement cases. All market sectors require this file.

District Definition File - Contains the district number and a qualitative description of the district.

In-Vehicle Travel Time File - One of the three "Other Changes Files" which contains times for in-vehicle travel that are not accounted for in the network analysis. The units are hundredths of minutes of travel on a zone-to-zone basis. For example, the entry "135", corresponds to 1.35 minutes. A base and improvement case file is necessary for market sectors for which the user chooses to input other in-vehicle travel time changes.

Out-of-Vehicle Travel Time File - One of the three "Other Changes Files", which contain times for out-of-vehicle or walk and wait travel that are not accounted for in the network analysis. The units are hundredths of minutes of travel on a zone-to-zone basis. For example, the entry "135", corresponds to 1.35 minutes. A base and improvement case file is necessary for market sectors for which the user chooses to input other out-of-vehicle travel time changes.

Out-of-Pocket Cost File - One of the three "Other Changes Files", which contain out-of-pocket costs that are incurred during a trip. These costs may be items such as tolls or parking charges. The units are cents per trip on a zone-to-zone basis. A base and improvement case file is necessary for market sectors for which the user chooses to input other out-of-pocket cost changes.

Production/Attraction or Trip Table Files - This file contains the market sector trip table that is used to estimate benefits and costs in the analysis. The trip table includes all person trips on a zone-to-zone basis for that market sector during the specified period. A base and improvement case trip table file is required for all market sectors.

Different types of market sectors require different input files depending on what type of analysis is being performed. Generally, the auto, truck, and carpool market sectors use the network analysis to estimate travel times and therefore require network input and output files. Transit market sectors do not have networks to estimate travel times but rely on input travel times through the "Other Changes Files". The following exhibit shows the files used by typical market sectors.

Exhibit 3.1 Typical Market Sector

Input Files

Auto/
Truck

Local Bus/
Exp. Bus

Light Rail/
Heavy Rail

Base Case Network File

X

   

Base Case Network Output File

X

   

Imp. Case Network File

X

   

Imp. Case Network Output File

X

   

Zone Information File*

X

X

X

Base Case In-Vehicle Travel Time File

 

X

X

Imp. Case In-Vehicle Travel Time File

 

X

X

Base Case Out-of-Vehicle Travel Time File

 

X

X

Imp. Case Out-of-Vehicle Travel Time File

 

X

X

Base Case Out-of-Pocket Cost File

**

X

X

Imp. Case Out-of-Pocket Cost File

**

X

X

Base Case Trip Table File*

X

X

X

Imp. Case Trip Table File*

X

X

X

Market Sector Output File*

X

X

X

*Required for all market sectors.
**May be needed if tolls are charged.

3.2.1 Layout of Network Files

Exhibit 3.3 presents the layout of the network files that are used in the network analysis module of STEAM 2.0. The file is a space-delimited ASCII format file with 7 columns, one for each field. No header information is included in the file. Each line represents a link on the network. The fields are described below:

A-Node - The beginning node of a link. The range of permissible values is 1-99,999.

B-Node - The ending node of a link. The range of permissible values is 1-99,999.

Exhibit 3.2  Layout of the Network Files

A-Node

B-Node

Length

FFsp

Capacity

Volume

Class

1

2

0.3

20

350

650

5

1

4

0.4

20

350

735

5

1

5

0.7

50

2,100

20,323

2

1

7

0.1

40

1,000

12,235

3

2

1

0.1

20

350

555

5

3

6

1.2

55

3,000

22,234

1

Continued for the entire network.

Length - The length in miles from A-Node to B-Node. Length must be greater in value than 0 and less than or equal to 99.

FFSp - The free-flow design speed for a link in mph. Free-flow speed must be greater in value than 0 and less than or equal to 99. Note that when the "use input free-flow speed option is chosen, this field should contain the loaded highway network speeds from a valid traffic assignment."

Capacity - The hourly one-way vehicular capacity of a link. Capacity must be a value greater than 0 and less than, or equal to 99,999.

Volume - The 24 hour average weekday traffic (AWDT) on the link. Volume must be a value greater than or equal to 0 and less than or equal to 1,000,000.

Class - The highway class of the link (the model can handle up to six highway classes). (The default assumptions are:

1=Interstates
2=Other freeways and expressways
3=Other principal arterials
4=Minor arterials
5=Collectors
6=local
7=centroid connectors

Class must be coded as a value between 1 and 7. Care must be taken in coding the highway classes, as these are used for assigning the proper speed equation to links in the highway network and for assigning the proper accident rate. Additionally, all links coded with a "7" will not be considered as "through links" in the travel time analysis. Non-centroid links coded with 0 capacity will be ignored in the travel time analysis.

Exhibit 3.3 presents the layout of ??? network files that are used in the network analysis module of STEAM 2.0. The file is an ASCII format file with seven columns, one for each field. No header information is included in the file. Each line represents a link on the network.

3.2.2  Layout of the Zone Information File

Exhibit 3.4 presents the layout of a zone information file which defines the attributes of each zone. Each record contains four columns, each of which is separated by spaces: zone number, and optionally (at a minimum zeros must be provided), district number, population and employment. No header information is included in the file. Each line represents a different zone in the analysis. The fields are described below:

Zone - The zone number used in the analysis.

District - The district number identified with the zone (optional). Districts are used for the zonal aggregation of user benefits and certain demand outputs.

Population - Zonal population for the analysis year (optional). Population is used by the accessibility analysis and to report per-capita user benefits by district.

Employment - Total zonal employment for the analysis year (optional). Employment is used by the accessibility analysis.

If a district-level aggregation of results is not desired, users can simply enter zero in the district field. If no accessibility analysis is desired, zeroes may be entered for the population and employment fields as well.

Exhibit 3.3  Zone Information File Layout

Zone

District

Population

Employment

1

1

345

8

2

1

1,558

181

3

16

55

1,006

4

16

172

1,184

5

2

551

1,274

6

2

201

4,344

Continued for the entire file.

As is shown in the example above, the zonal information file is sorted by zone.

3.2.3  Layout of District Definition File

The district definition file contains two data items, the district number and the district name, or some other description of the district. A four-zone example is shown below.

Exhibit 3.4  District Definition File Layout

District Number

District Name

2

"District two"

9

"District nine"

12

"District twelve"

11

"District eleven"

14

"District fourteen"

As shown above, the district name should be enclosed in quotes. Comments are allowed in the file; these should appear on a separate line, and be preceded by an exclamation (!) mark.

3.2.4  Layout of Other Changes Files

Exhibit 3.4 presents the layout of the other changes files (in-vehicle travel time file, out-of-vehicle travel time file, and out-of-pocket cost file). Zero value interchanges may be omitted from the file. The files are in ASCII format and are in space-delimited origin/destination/value format. No header information is included in the file. The exhibit below shows the input file for origin zone one and destination zones 1-4. Values for the Other Changes files are expressed in the following units:

Exhibit 3.5  Layout of Other Changes Files 

Origin Zone

Destination Zone

Value

1

2

473

1

3

0

1

4

335

1

5

734

3.2.5  Layout of Production/Attraction or Trip Table Files

Exhibit 3.4 presents the layout of the market sector production/attraction or trip table files. The files are in ASCII format and are in production/attraction/value or origin/destination/value format. Zero value interchanges may be omitted from the file. No header information is included in the file. The exhibit below shows a sample input file for origin zone 1 and destination zones 1-4. Note that STEAM 2.0 evaluates table flows based on person, rather than vehicle trips. Estimates of VMT and VHT are derived from the vehicle occupancy factors entered in the market sector information screen, which is described in Chapter 4.

Exhibit 3.6  Layout of Trip Table Files

Origin Zone

Destination Zone

Value

1

2

553

1

3

300

1

4

34

Note that intrazonal trips are ignored by STEAM 2.0.

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3.3 Output Files

STEAM 2.0 presents the results of an investment analysis in several different formats organized across different levels of aggregation. These files include:

3.3.1  Main Scenario Report File

The main scenario file (.bsn), is organized around fourteen outcome sections which present improvement case, base case and net results across modes. The report file includes a list of all input parameters, as well as a notification when STEAM 2.0 finds zone pairs that are disconnected or have zero travel times.

The report file is a text file is accessible from the STEAM 2.0 user interface, which invokes the Microsoft program Notepad (or any other compatible text editor program that can be selected under the "Tools/Reporting Options" menu). For best viewing results, the size of the font should be set to eight. For best printing results paper orientation should be set to Landscape. The outcome parameters include:

  1. Demand: Person trips, VMT, person trips, IVT, OVT, total travel time;
  2. Emissions: Running (HC,CO,NOx, PM10), Cold Start (HC,CO,NOx, PM10), Total;
  3. Emissions Costs: Running, Cold Start, Total;
  4. Greenhouse Gas Emissions: BTU Consumption, CO2 Emissions, Greenhouse Gas Costs;
  5. Accidents: Internal Accidents ( Fatalities, Injuries, Property Damage Only, Total) External Accident Costs: (Fatalities, Injuries, Property Damage Only, Total);
  6. Fuel and Non-fuel Costs: Gallons Consumed, Energy Costs, Non-Fuel Operating Costs;
  7. External Costs: Noise Costs, Other Mileage-based External Costs, Non-mileage-Based External Costs, External Costs During Construction;
  8. User Benefits: IVT, OVT, Fuel Costs, Non-fuel Operating Costs, Out-of-pocket Costs, Internal Accident Costs, Revenue Transfers;
  9. Public Vehicle Operating Costs;
  10. Capital Costs: Capital Costs, Salvage Values, Annualized Costs, Other Maintenance Costs, Operating Costs;
  11. Summary: User Benefits by Category, Costs to Public Agencies by Category, Net Annual Worth, Benefit-Cost ratio;
  12. Scenario Assumptions;
  13. Market Sector Definitions; and
  14. Risk Analysis Output.

A binary image of the main report file (.brp extension) is created during a STEAM 2.0 analysis. This file is used for secure temporary storage of all input parameters used by STEAM 2.0. This file should not be deleted during a STEAM 2.0 analysis.

3.3.2  Market Report Files

STEAM 2.0 produces three separate reports based on market sectors: 1) spreadsheet-compatible file (.mkx extension); 2) a text-base file (.mkr extension); and 3) database-compatible file (.mkd extension). The market sector files provide results at the regional level organized by market sector.

The spreadsheet-ready market report file (.mkx extension) presents analysis results for each market and mode, and is organized for easy comparison across base and improvement cases. The file may be edited within the spreadsheet application to produce charts, additional summary or cross-tabulation tables. Within each report section, each column presents results for a distinct mode and market sector. Outputs are structured around six sections:

  1. Demand: Person trips, VMT, person trips, IVT, OVT, total travel time;
  2. Emissions: Running (HC,CO,NOx, PM10), Cold Start (HC,CO,NOx, PM10), Total;
  3. Benefits: IVT, OVT, non-fuel costs, total benefits, revenue transfers;
  4. Accessibility by travel time intervals: district population to regional jobs and district jobs to regional labor pool;
  5. Accessibility by travel time intervals: Percentage of district population to regional jobs and percentage of district jobs to regional labor pool; and
  6. Accessibility index: District population to regional jobs and district jobs to regional labor.

Sample output from this file is presented in Exhibit 3.7.

Exhibit 3.7  Spreadsheet-Ready Market Sector Report File

Spreadsheet-Ready Market Sector Report File

 The .mkr file is a text file which may be read from any text editor, such as MS Wordpad or MS Notepad. The layout of the file is identical to that of the spreadsheet-ready file. As described in Chapter 4, users may define the number of columns per row of output under the "Tools/Select Text Editor" menu option. Setting the number of columns to fit within the page width will prevent text wrapping. At an eight point font, up to seven columns of output per row can be printed in landscape format without text wrapping.

The database-ready market report file (.mkd extension) presents outputs in normalized format, i.e., the rows of each column contain unique information. This allows for easy importation of results into commercial database applications, such as Access, Oracle or FoxPro, and for the development of database queries using the structured query language (SQL). Each output parameter is associated with a market, mode, expansion factor, parameter number, parameter name and parameter value. Exhibit 3.8 presents the output parameters presented in this file.

Exhibit 3.8  Database-Compatible Market Report File Outputs

Demand Outputs

Benefit Outputs

Accessibility Outputs

Productions/Attractions

IVT/OVT

Population to Jobs
(by travel time threshold)

Vehicle Miles of Travel

Fuel Cost

Jobs to Labor
(by travel time threshold)

Person Miles of Travel

Non-Fuel Costs

Index: Population to Jobs

Person Trips

Total Benefits

Index: Jobs to Labor

IVT/OVT/Total Travel Time

Revenue Transfers

Total Population
Total Jobs

Exhibit 3.9 presents a sample of the format of the .mkd file.

Exhibit 3.9  Database-Compatible Market Report File

 Database-Compatible Market Report File

3.3.3  District Report Files

A STEAM 2.0 analysis produces three files which organize results by user-defined districts: 1) a text-based file (.dkx extension), 2) a spreadsheet-compatible file (.dkx extension); and 3) a database-compatible file (.dkd extension). Each of these files provide selected results for each district, by market and by mode.

The spreadsheet-ready district report file (.dkx extension) presents analysis results for all districts, markets and modes organized for easy comparison across base and improvement cases. The file may be edited within the spreadsheet application to produce charts or additional summary tables. Within each district section, each column contains results for a distinct mode and market. Outputs are structured around six sections:

  1. Demand: Person trips, VMT, person trips, IVT, OVT, total travel time;
  2. Benefits: IVT, OVT, non-fuel costs, total benefits, revenue transfers;
  3. Accessibility by travel time intervals: district population to regional jobs and district jobs to regional labor pool;
  4. Accessibility by travel time intervals: Percentage of district population to regional jobs and percentage district jobs to regional labor pool;
  5. Accessibility index: District population to regional jobs and district jobs to regional labor; and
  6. Summary: At the end of the file, the summary section reports, for each district, total benefits, percentage of total regional benefits, per capita benefits, change in VMT, VHT, change in PMT (person miles of travel), change in PHT (person hours of travel), change in productions and change in attractions.

Sample output from this file is presented in Exhibit 3.10.

The .dkr file is a textual file which may be read from any text editor, such as MS Wordpad or MS Notepad. The layout of the file is identical to that of the spreadsheet-ready file. When printing output from this file, the text will wrap around to additional rows of output, to accommodate the width of each output row. At an eight point font, up to seven columns of output per row can be printed in landscape format without text wrapping.

Exhibit 3.10  Spreadsheet-Ready District Output File

 Spreadsheet-Ready District Output File

The database-ready district report file (.dkd extension) presents outputs in normalized format, i.e., the columns of each row contain unique information. This allows for easy importation of results into commercial database applications and for the development of database queries using the Structured Query Language (SQL). Each output parameter is associated with a district, market, mode, expansion factor, parameter number, parameter name and parameter value. Exhibit 3.11 below presents the output parameters presented in this file.

Exhibit 3.11  Database-Compatible District Report File Output Parameters

Demand Outputs

Benefit Outputs

Accessibility Outputs

Productions/Attractions

IVT/OVT

Population to Jobs
(by travel time threshold)

Vehicle Miles of Travel

Fuel Cost

Jobs to Labor
(by travel time threshold)

Person Miles of Travel

Non-Fuel Costs

Index: Population to Jobs

Person Trips

Total Benefits

Index: Jobs to Labor

IVT/OVT/Total Travel Time

Revenue Transfers

Total Population
Total Jobs

Exhibit 3.12  Sample of the Format of the .dkd File

 Sample of the Format of the .dkd File

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3.4  Network Output Files

STEAM 2.0 generates network output files (.ttf extension) for storage of zone to zone travel times and distances during a STEAM 2.0 analysis. One each is generated for the base and improvement cases. Once a .ttf file has been generated, it can be used in subsequent analyses by disabling the "Run (base/improvement) Network Analysis" option in the Network and Trip Table File Name screen used to set up a STEAM 2.0 analysis. These files are stored in binary format and cannot be accessed by the user.

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3.5  Excluded Zone Pairs File

Zone pairs for which a travel time cannot be determined in either the base case or the improvement case are excluded from the user benefits calculation. For example, STEAM 2.0 cannot calculate shortest time paths between a zone pair on the highway network if all centroid connectors from or to a particular zone are missing. Likewise, STEAM 2.0 will ignore zone pairs for which an in-vehicle time exists only in the base or improvement cases, but not in both cases. This may occur when brand new transit services are being evaluated in the improvement case, for example. User benefits for such cases should be evaluated off-line. STEAM 2.0 produces output files for such off-line evaluation.

Zones excluded from the analysis are reported in the .bsx (base case) and .ipx (improvement case) files. The file contains the origin zone, destination zone, the number of trips in the base and improvement cases and the cause for the exclusion, respectively. The cause for exclusion is denoted by a "0" or an "X", where "0" denotes a zero travel time, while an "X" indicates that no travel time could be determined. This text file can be imported to a spreadsheet application for further analysis. An example of this file format is shown in Figure 3.16 below.

Exhibit 3.13  Sample .ipx/.bsx File Format

 Sample .ipx/.bsx File Format

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