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Table of Contents 

page 

1. INTRODUCTION ........................................................... 1 


1.1 What is the COMMUTER model? ....................................... 1 


1.2 Who will use COMMUTER? ........................................... 1 


1.3 Why was COMMUTER created? ....................................... . 1 


1.4 What Programs can I evaluate with COMMUTER? ......................... 2 


1.5 What methodology does COMMUTER use? ............................... 2 


1.6 When can I use COMMUTER, and when should I not use it? .................. 3 


1.7 What do I need to do to get started? ...................................... 4 


1.8 What other documentation is available? ................................... 5 


1.9 What has Changed Compared to COMMUTER Version 1.0? .................. 5 


2. USING THE MODEL ....................................................... 7 


2.1 What type of computer equipment and software do I need? .................... 7 


2.2 How do I install and operate COMMUTER? ............................... 7 


2.3 How do I begin once the program is installed? ............................. 10 


2.4 How do I input data? ................................................. 11 


2.5 Is there help available when inputting data? ............................... 14 


2.6 Can I save my inputs to use in another analysis? ........................... 16 


2.7 Can I use my own emission factors? ..................................... 16 


2.8 How do I view the results? ............................................ 18 


2.9 How do I print my data and results? ..................................... 19 


2.10 Can I tell the model to remember where my files are stored? ................ 21 


2.11 What do I do when I’m finished? ...................................... 22 


3. GENERAL INPUT SCREENS ................................................ 23 


3.1 Scenario Information ................................................ 23 


3.2 Local Data ......................................................... 28 


3.3 Edit Coefficients .................................................... 32 


4. TCM-SPECIFIC DATA ..................................................... 35 


4.1 Site Access and Transit Service Improvement Programs ..................... 35 


4.2 Financial Incentive and Parking Cost Programs ............................ 39 


4.3 Site-Specific Employer Support Programs ................................ 41 


4.4 Area-Wide Employer Support Programs ................................. 45 


4.5 Alternative Work Schedule Programs .................................... 46 


5. EMISSIONS-RELATED INPUT SCREENS ..................................... 50 


5.1 Fleet Emissions Information ........................................... 50 


5.2 Other Emissions-Related Data ......................................... 55 


6. REFERENCES ............................................................ 59 


i 
List of Tables 

page


Table 1 Summary of COMMUTER Data Inputs ......................... 12 


Table 2 Default Speeds (mph) by Area Size ............................. 58 


List of Figures 

page


Figure 1 COMMUTER Startup Screen .................................. 9 


Figure 2 Menu Structure ............................................. 11 


Figure 3 Model Layout Screen ........................................ 15 


Figure 4 Sample Output Report ....................................... 20 


Figure 5 Scenario Information Input Screen ............................. 24 


Figure 6 Local Data Input Screen ...................................... 30 


Figure 7 Edit Coefficients Input Screen ................................. 34 


Figure 8 Site Access and Transit Improvements Input Screen ................ 36 


Figure 9 Financial Incentives Input Screen .............................. 39 


Figure 10 Site-Specific Employer Support Programs Input Screen ................... 42 


Figure 11 Area-Wide Employer Support Programs Input Screen .................... 46 


Figure 12 Alternative Work Schedules Input Screen .............................. 48 


Figure 13 Fleet Emissions Information Input Screen .............................. 51 


Figure 14 Other Emissions-Related Data Input Screen ............................ 56 


ii 
1. INTRODUCTION 

1.1 What is the COMMUTER model? 

The COMMUTER model (subsequently referred to as simply “COMMUTER”) is a 

spreadsheet-based computer model that estimates the travel and emissions impacts of 

transportation air quality programs focused on commuting. The model is particularly 

useful for programs such as those recognized under the EPA’s Best Workplaces for 

CommutersSM and other Commuter Choice Programs. 

1.2 Who will use COMMUTER? 

EPA designed COMMUTER for two types of users: 

•	 Metropolitan Planning Organizations (MPOs) and state Departments of 

Transportation (DOTs) who are assessing emissions impacts of various 

Transportation Control Measure Strategies. These impacts can be incorporated 

into State Implementation Plan (SIP) analyses. 

•	 Individual employers who are assessing the likely effectiveness of various 

commuter benefit packages and other measures to facilitate use of commute 

alternatives. 

MPOs and DOTs can also provide guidance and assistance to employers participating in 

voluntary programs on the application of this tool. 

1.3 Why was COMMUTER created? 

COMMUTER was designed to help simplify the effort required by air quality planners to 

estimate travel and emission effects resulting from Transportation Control Measures. The 

model can also be used to estimate the benefits of site-specific Commuter Choice 

(employer-based transportation) programs to assist employers in designing a program 

appropriate for them. 

The 1990 Clean Air Act Amendments mandated that the EPA and DOT provide guidance 

on “the formulation and emission reduction potential of transportation control measures 

related to criteria pollutants and their precursors” (Section 108(f)). In the early 1990s, 

EPA developed a number of tools and guidance documents to assist communities in 

developing these measures and taking credit for the resulting emission reductions. 

Because the effects of TCMs on travel activity and emissions can be very complex, the 

1

guidance included many aspects of vehicle operation and other factors that affect 

emissions. The guidance documents were often very detailed and difficult to use. 

COMMUTER consolidates existing TCM guidance, and is based on “state-of- practice” 

methodologies and data. COMMUTER will reduce the time required to calculate the 

benefits of regional and employer-based TCMs. It will also save regional government 

resources, since these governments will have less need to develop their own models and 

tools. 

1.4 What Programs can I evaluate with COMMUTER? 

You can use COMMUTER to evaluate these types of programs, either for a defined 

region within an urban area, or for individual employers: 

•	 Transit fare decreases or other incentives that reduce the cost of using transit; 

•	 Transit service improvements (faster or more frequent service); 

•	 Ridesharing programs, in which employers support carpooling and/or vanpooling 

through on-site programs, financial incentives, or preferential parking; 

•	 Other actions, such as increased parking charges or cash-out programs, that 

change the time and/or cost of traveling by any particular mode; 

•	 Non-motorized (e.g., bicycle and pedestrian) commuting programs; 

•	 Alternative work schedules, including flex-time, compressed work weeks, and 

staggered work hours; and 

•	 Telecommuting. 

1.5 What methodology does COMMUTER use? 

COMMUTER is broken down into two components: travel impacts and emissions 

impacts. 

The travel impacts component uses a logit mode-choice model referred to as the “pivot 

point” approach. This approach allows you to analyze the effects of several strategies 

simultaneously. Mode choice models have been developed for many cities and regions 

nationwide, so you can often use coefficients that have already been developed to reflect 

local characteristics. This component will calculate the impact of the mode share changes 

2

from these programs and translate the mode share changes into changes in trips and 

vehicle miles traveled (VMT). In addition, COMMUTER contains an input option that 

allows you to enter mode share changes directly (such as might be obtained from 

employee survey data) as an alternative to the pivot point-based calculation performed 

internally by the model. 

The emissions component is based on EPA’s MOBILE6.2 model. MOBILE6.2 emission 

factors were generated and loaded into COMMUTER for several sets of local conditions. 

You can select the conditions most appropriate for your area, and the model will apply 

the corresponding emission factors in calculating and outputting emission reduction 

impacts. If you are an experienced MOBILE6.2 user, you can also generate your own set 

of MOBILE6.2 emission factors (reflecting your exact local conditions) that can be 

imported into COMMUTER. In fact, if you intend to use COMMUTER to produce 

emissions reduction estimates for SIP submittals or conformity determinations, your 

emission outputs from COMMUTER must be based on an imported MOBILE6.2* run 

using your own local or state information. See the BWC SIP and Conformity Guidance 

for more information on how to include control measures from BWC programs in SIPs 

and conformity determinations. 

1.6 When can I use COMMUTER, and when should I not use it? 

COMMUTER is particularly useful for smaller Transportation Control Measures and can 

be used for the purpose of calculating State Implementation Plan (SIP) credit or for 

conformity determinations. The model will not perform as well for larger programs, 

particularly those large enough to impact travel speeds throughout an area. If your 

program is likely to have a regionally significant effect on travel patterns** it must be 

analyzed within the modeling performed by the MPO during its regional emissions 

analysis You should consult with your regional EPA office if you believe your program 

can have these impacts. In this case, you can still use COMMUTER to calculate an 

initial estimate of a potential program. You may want to do this to help you select a 

program and determine if you want to further consider particular options. 

* EMFAC is required for SIP modeling in California. COMMUTER does not have the ability to import 

EMFAC emission factor output. 

** 40 CFR 93.101 defines a “regionally significant” project as “a transportation project (other than an 

exempt project) that is on a facility which serves regional transportation needs (such as access to and from 

the area outside of the region, major activity centers in the region, major planned developments such as new 

retail malls, sports complexes, etc., or transportation terminals as well as most terminals themselves) and 

would normally be included in the modeling of a metropolitan area's transportation 

network, including at a minimum all principal arterial highways and all fixed guideway transit facilities that 

offer an alternative to regional highway travel.” 

3 
IMPORTANT: COMMUTER is not designed to quantify baseline 

travel or emissions. Instead, its purpose is to estimate travel and 

emission changes associated with specific measures, based on 

inputs you provide. Thus, although COMMUTER may be used to 

calculated SIP credits for these measures, the baseline travel or 

emissions estimates it generates will not exactly match your 

baseline SIP inventory. 

The COMMUTER Model is most appropriately applied to a single worksite, employment 

center, or subarea for sketch-level analysis purposes. Its most robust predictive power 

lies with measures that can be translated into time and cost strategies. The factors used 

for employer support and alternative work arrangements are based on the best research 

and professional judgment available. In most cases, though, the empirical evidence to 

support these factors is very limited. Furthermore, the impacts of any one type of 

program can vary substantially, depending upon the characteristics of the worksites being 

evaluated, the employees who work there, and how effectively a given program is 

implemented. For some planning purposes, therefore, it may be necessary to gather 

additional empirical data and/or conduct more detailed modeling, in order to increase the 

reliability of the estimate of a program’s impacts. 

1.7 What do I need to do to get started? 

In order to run the model, you will need to gather background information about the 

travel characteristics in your area. MPOs or Councils of Government (COGs) generally 

compile this information for an area. Regional COGs are local government organizations 

designed to study and recommend solutions to problems facing an individual region and 

to help their local government members apply effective, coordinated regional planning. 

MPOs are similar organizations that focus on transportation-related planning. 

If you are an employer or other non-MPO user of this model, you should contact the MPO 

or COG in your area. The National Association of Regional Councils (NARC) maintains 

an Internet website at http://www.narc.org. From the NARC home page, you can access 

information about the Association of Metropolitan Planning Organizations (AMPO) and 

lists of COG and MPO links by state (http://www.narc.org/links/member.html). If you are 

unsure of the appropriate source, you should consult with your regional EPA office to find 

the appropriate source of information. 

4

You will also need specific background information for your particular program. This 

user manual will assist you in determining the appropriate inputs into the model. Again, 

if you have any further questions, you can consult with your regional EPA office. 

1.8 What other documentation is available? 

This user manual presents the key instructions needed for you to effectively develop 

inputs and run COMMUTER. Although it attempts to provide you with enough 

information to understand how to develop inputs and operate the model, it is not 

exhaustive in detail. If you are interested in further understanding the theory behind the 

modeling calculations, please consult the companion document to this user manual, 

“Procedures Manual for the COMMUTER Model v2.0.”1* 

1.9 What has Changed Compared to COMMUTER Version 1.0? 

COMMUTER Model version 1.0 was originally released in 2000. Version 2.0, released 

in 2005, incorporates a number of updates and changes to calculation procedures, to make 

use of the most recently available travel and emissions data and to expand the model's 

capabilities. Significant changes include the following: 

•	 The default travel parameters (e.g., mode shares, trip lengths) have been updated 

using data from the 2000 U.S. Census, the 2001 Nationwide Household 

Transportation Survey, and other recent sources. 

•	 The default and area-specific mode choice coefficients have been updated based 

on a review of current national practice. Default coefficients are no longer 

provided for different area sizes, since a review of the coefficients did not find 

significant differences among urban areas of different sizes. 

•	 Some of the TCM impact values embedded in the model have been updated, 

based on recent research. These include the mode share impacts for "level 3" and 

"level 4" carpooling and vanpooling support, and default participation level for 

telecommuting programs. 

•	 Emissions are now calculated using MOBILE6.2, EPA's most current version of 

the MOBILE emission factor model, rather than MOBILE5b. 

•	 Emissions are reported for seven additional pollutants, including particulate 

matter (PM2.5, users can get PM10 output by importing their own MOBILE6.2 

runs with PM10 output) and six air toxics, as well as for the four pollutants 

originally reported by COMMUTER - volatile organic compounds (VOC), carbon 

monoxide (CO), oxides of nitrogen (NOx), and carbon dioxide (CO2). Emissions 

for some pollutants are now reported in pounds per day as well as in tons per day. 

* Superscripts denote references provided in Section 6. 

5 
•	 The procedure for calculating emissions changes has been revised for consistency 

with MOBILE6.2 format emissions data. Additional user inputs may be 

specified, including the percentage of vehicle-miles of travel (VMT) by facility 

type, and average travel speeds for both freeways and arterials in both the peak 

and off-peak periods. On the other hand, user inputs for the percentage of cold 

starts are no longer required. 

6

2. USING THE MODEL


This section explains how to install COMMUTER and provides a general overview of 

how to run each element of the program, as well as how to view and save your results. 

Further details on the type of data required are provided in Section 3 (for general existing 

condition inputs), Section 4 (TCM-specific information), and Section 5 (emissionsrelated information). 

2.1 What type of computer equipment and software do I need? 

COMMUTER runs on personal computers using Microsoft’s Windows 95 or later 

operating systems. You must also have Microsoft Excel 95 (i.e., Excel 7.0) or a more 

recent version of Excel installed. If your computer allows you to run these programs, you 

can use COMMUTER. (However, if you have a Pentium-class CPU with less than 150 

MHz, moving through the input screens may be slow at times.) 

COMMUTER will work at 640 x 480, 800 x 600, and 1,024 x 768 display resolutions at 

both 250-color and 16-bit (Hi-Color) depths, and should run at any available video 

display setting. 

The COMMUTER model itself requires a minimum of 2.0 MB of disk space. In 

addition, the default MOBILE6 emission factors that may be used with the model are 

provided in 192 external tab-delimited data files (.tbz) that require 12.2 MB when zipped 

or 47.4 MB when unzipped. If disk space is a concern, the user may choose to retain only 

the files that are relevant to their analysis area. If the user chooses to provide their own 

MOBILE6 outputs, the output file will require approximately 40 MB of disk space. 

2.2 How do I install and operate COMMUTER? 

Installing the Program 

Installing COMMUTER is quite simple. The model, along with some sample files, is 

contained in the COMM1.EXE self-extracting archive file (which can be downloaded 

from EPA’s web site at http://www.epa.gov/otaq/transp.htm). Step-by-step installation 

instructions are given as follows. 

Step 1 - Create a new folder or directory on your computer where you want to install 

and operate COMMUTER (e.g., C:\COMMUTER). (When you run COMMUTER, it 

can create and re-use “scenario” files that store your data and assumptions for a 

7

particular analysis case or scenario. Thus, it is highly recommended that you create a 

separate folder for COMMUTER so these files don’t get mixed up with others.) 

Step 2 - Download or copy the COMMUTER_v20.ZIP file to your computer and 

unzip it, directing it to deploy all files to the folder or directory you just created. 

When this is complete you should have a folder entitled “COMMUTER_v20" within 

the directory you’ve chosen with the following items: the model itself, 

COMMUTER_v20.xls; an example scenario file entitled Example Scenario_v20.vme; 

a sample MOBILE6.2 input file entitled M6sample.in; and a folder entitled Data 

containing 192 files with a .tbz extension. These files contain data related to the 

Petroleum Administration for Defense Districts (PADDs) that are needed to compute 

changes in emissions of air toxics. It is important that the Data folder be in the same 

folder as COMMUTER_v20.xls. If the Data folder is in a different location, 

COMMUTER will be unable to access the files. 

Finally, you should check your macro security level in Excel to ensure that it is set on 

“Medium.” This is done by opening the “Tools” menu, selecting “Macro,” and then 

selecting “Security.” You will have a choice of High, Medium, or Low security. Select 

Medium. COMMUTER’s macros will not run if the security level set to High, and Low 

is not recommended. 

Running the Program 

Once you have installed the program, there are several different ways that you can run the 

program. 

•	 Create and launch a shortcut to the application; 

•	 Double-click* the COMMUTER_v20.xls file from within the Windows Explorer 

or Internet Explorer window (assuming Excel has been installed and associated 

with .XLS file types); 

•	 Right-click the COMMUTER_v20.xls file and click “Open” from the pop-up 

menu; or 

•	 Click the Start button at the bottom left of the Windows desktop, select 

“Documents” from the pop-up menu, and then click the COMMUTER_v20.xls 

file from the pop-up list of documents. (This method will work only if you have 

* If the Windows Explorer has been replaced by Internet Explorer (e.g., in Windows 98), Internet Explorer 

can be configured to launch programs with a single mouse click instead of a double-click. 

8 
recently opened the COMMUTER_v20.xls file and it still appears in your 

“Recent Documents” list.) 

You cannot run the program by launching a previously created scenario file (.vme) from 

the Windows desktop. Scenarios must be opened from within the program after it has 

been launched in one of the ways described above. As the program launches you will see 

a dialogue box stating that the file has macros and asking you to choose when to disable 

the macros or enable them. Select “Enable Macros.” As the program loads, you will see 

a startup screen like the one shown below in Figure 1. 

Figure 1


COMMUTER Startup Screen


COMMU T E R MODE L 

COMMU T E R CH OI CE & VOL U N T AR Y MOB I L E S OU R CE P R OGR AM 

T R AVE L AND E MI S S I ONS ANAL YS I S T OOL 

Release 

1.0 

INPUT LEGEND

 - REQUIRED INPUT

 - OPTIONAL INPUT

 - LOCKED CELLS 

- PROGRAM-CONTROLLED CELLS

 - HELP TEXT 

The startup screen includes an “input legend” showing the colors that are used to identify 

the different types of cell ranges that you will see on the data entry screens. Different 

colors are used to identify cells that you type inputs into and to highlight on-screen help 

boxes as listed below: 

• light green - required input cells; 

• yellow - optional input cells; 

• white - locked (i.e., non-editable) cells; 

• gray - program-controlled cells; and 

• red - help text boxes. 

9

Required inputs must be typed into all light-green cells shown in the edit screens. You 

can also supply inputs in the yellow shaded cells, but the program will run if they are left 

blank. (However, it is a good idea to use these optional input cells to supply more 

information about the analysis scenario you are constructing.) White and gray cells are 

locked from editing and are used to display information. Finally, red cells highlight help 

boxes containing brief instructions for the inputs being entered on each screen. 

NOTE: When the program has finished loading, you will see a 

“Ready” indicator at the bottom left of the application window. 

The user interface for COMMUTER has been programmed to display on your entire 

screen (i.e., in “full” screen). If you need to temporarily minimize the COMMUTER 

application to the Windows taskbar (located at the bottom of the Windows desktop by 

default), type “Ctrl-m” (i.e., hold down the Ctrl key and type “m”). To restore the 

COMMUTER application to the full screen, just click its button in the Windows taskbar. 

2.3 How do I begin once the program is installed? 

Once the program finishes loading, you can select from four main menus listed at the top 

of the screen: the File menu, the Edit Inputs menu, the Results menu, and the Help menu. 

These menus will be available at the start of every session, and will allow you to enter 

data (Edit Inputs menu), view results (Results menu), print results (File menu), get help 

(Help menu), and retrieve or save data and results for a specific analysis (referred to as a 

“scenario”, accessed through the File Menu). 

Figure 2 shows the structure of the main menu, which includes the “File,” “Edit Inputs,” 

“Results,” and “Help” menus, and each of the sub-menu elements. 

You will generally begin an analysis by clicking through the data entry elements in the 

Edit Inputs menu in the order in which they are listed in the menu. (Once you have 

defined an analysis, you can later load and edit a scenario from the File menu; this will be 

discussed later in Section 2.6.) Each of the elements in the Edit Inputs menu corresponds 

to the input screens for entering specific data required by COMMUTER. (Detailed 

information on the data required for these screens is provided in Sections 3-5.) 

10

Figure 2


Menu Structure


File Menu Edit Inputs Menu


Results Menu Help Menu 

When the program is first loaded, some of the sub-menu elements shown in the Edit 

Inputs menu will be shown as gray shaded-out text, which indicates that you have not yet 

selected any TCM programs for analysis. (As explained below, you will make these 

selections by using the check boxes at the bottom of the Scenario Information screen.) 

2.4 How do I input data? 

The Edit Inputs menu lists each of the input screens available. Some of the screens are 

for inputting baseline (i.e., existing condition) information needed regardless of the type 

of TCM being analyzed; others will be used only when analyzing a particular measure. 

11

IMPORTANT: The program will automatically size the width of 

the data entry screens to the width of your monitor. However, the 

length of some of the screens will exceed the monitor’s vertical 

display dimension. Therefore, for some input screens (such as the 

Scenario Information and Local Data screens), you must scroll to 

the bottom of the screen to complete the data entry required in that 

screen by using the vertical scroll bar or the “Down Arrow” or 

“Page Down” keys. 

The information that must be entered in each input screen is listed in Table 1. The data 

required in the first three screens (“Scenario Information,” “Local Data,” and “Edit 

Coefficients”) consist of general information, background travel data, and mode-choice 

coefficients. 

Table 1 

Summary of COMMUTER Data Inputs 

Input Screen Data Required 

Scenario Information General information, including area size and scope (i.e., regional vs. sitespecific) being analyzed and the TCM programs being evaluated 

Local Data 

Background travel data such as existing mode shares, trip lengths, 

occupancy levels, baseline vehicle miles traveled, baseline speeds, and 

option to provide final mode shares (after TCMs) 

Edit Coefficients Provides default mode choice coefficients as a function of the area size 

entered earlier and for selected cities, which can be edited by the user 

Site Access & Transit 

Service Improvements 

Data required for analysis of either site access or transit service 

improvement TCMs, including changes in site access walk times and 

employer participation rates, and transit headway and route travel time 

changes 

Financial Incentives & 

Parking Costs 

Inputs for analysis of financial and parking incentive programs consisting 

of changes in parking, transit fare, or other costs by travel mode 

Site-Specific Employer 

Support Programs 

Parameters that specify either the program participation level or expected 

mode share increase resulting from the implementation of an employer 

(i.e., site) specific commuter choice program 

Area-Wide Employer 

Support Programs 

Employer participation level inputs required for area-wide analysis of 

commuter choice programs being implemented across a metropolitan area 

12

Table 1 

Summary of COMMUTER Data Inputs 

Alternative Work 

Schedules 

Existing and expected eligibility or participation rates for alternative work 

schedule programs being evaluated, such as flex time, compressed work 

weeks, staggered hours, and telecommuting 

Fleet Emissions 

Information 

Inputs required by the program in order to either apply a pre-generated set 

of MOBILE6.2 fleet emission factors or to utilize locally generated 

MOBILE6.2 emission factors imported into the model 

Other Emissions-Related 

Data 

Fleet travel mix (e.g., fraction of travel by vehicle class) and start fraction 

inputs required by the program to calculate TCM emission reductions that 

are specific to the local conditions being modeled 

If you have not yet done any analyses or want to analyze a new scenario, you will start 

with the Scenario Information screen to enter general background information and to 

select the type(s) of TCM programs being evaluated. This selection is made by checking 

the appropriate boxes shown at the bottom of the Scenario Information screen. You can 

enter any non-blank character in the check boxes to activate analysis of the specific 

TCMs. 

Travel data should be entered using the Local Data screen, and you can use the Edit 

Coefficients screen to edit the default mode choice coefficients provided with the 

program. (Images of these screens and details on the data required are provided in 

Section 3.) By default, COMMUTER calculates changes in mode share due to the types 

and extent of specific TCM programs being modeled. If , however, you have estimates of 

changes in mode share due to modeled programs, you can optionally enter the final mode 

shares (resulting from changes to existing shares) in the Local Data screen. 

Data for the specific TCM program(s) being evaluated are entered in the next five 

screens. You will have access to only those screens that were selected (checked off) for 

analysis in the Scenario Information screen. Detailed information on these screens is 

provided in Section 4. 

NOTE: If you have chosen to enter your own final mode share 

estimates in the Local Data screen, you do not need to enter 

information in any of the TCM-specific program screens. In this 

case, the inputs in these screens are bypassed and the final mode 

shares you have entered are used to computeVMT and trip impacts. 

13

Finally, you will enter emission-related data in the last two data screens (addressed in 

Section 5). This will include either vehicle fleet parameters that allow the program to 

find and apply a specific set of previously generated MOBILE6.2 emission factors that 

approximate local conditions being modeled, or selection of MOBILE6.2 emission 

factors that you have generated to more precisely reflect local conditions. 

NOTE: You may see a “Calculate” annunciator on the status bar 

at the bottom of the application window while you are entering 

data. This is normal. During data entry, the program recalculates 

only specific portions of the underlying spreadsheets in order to 

speed up performance. Later, when you view or print results or 

save the scenario data, all underlying sheets are recalculated. 

If you are only interested in computing travel impacts, you do not need to enter any 

emissions-related inputs in these last two screens. 

2.5 Is there help available when inputting data? 

From the Help menu, you can view a “Model Layout” screen that provides an overview 

of the layout and data flow of COMMUTER. The Model Layout screen also identifies 

the input screens that apply to specific voluntary measures and commuter choice 

programs. Figure 3 shows the Model Layout screen. Note that on smaller monitors, you 

may need to scroll down to view the entire screen. 

You can also return to the Startup screen from the Help menu. (This is handy if you need 

to refer to the cell coloring conventions used to guide you in entering model inputs.) 

In addition, many of the input screens offer additional guidance on the specific data that 

must be entered. In some screens, explanatory notes are shown next to the input cell. In 

other screens, “help boxes” displayed with light red backgrounds provide more extensive 

descriptions of key data inputs. 

Once you’ve finished inputting all the required data for each screen (remember that in 

some cases you may need to scroll down your screen to complete data entry), that screen 

will appear with a checkmark (�) beside it the next time the Edit Inputs menu is 

accessed. You can use the presence or absence of checkmarks as an easy visual reference 

of additional data that must still be entered. 

14

Figure 3


Model Layout Screen


COMMUTER MODEL DATA LAYOUT 

(SCROLL DOWN TO VIEW ENTIRE LAYOUT SCREEN) 

GENERAL INPUT SCREENS 

SCENARIO INFORMATION LOCAL DATA MODE CHOICE MODEL COEFFICIENTS 

General Information Existing Mode Shares Choice of: 

Analysis Area Definition Existing Trip Length National Defaults 

Analysis Area Employment Existing Occupancy City-Specific Defaults 

TCM Programs Being Analyzed Peak Period Info User-Specified 

Observed Mode Shifts 

from TCMs (optional) 

TCM PROGRAM-RELATED INPUT SCREENS 

SITE-SPECIFIC PROGRAMS AREA-WIDE PROGRAMS 

SITE ACCESS IMPROVEMENTS (NO TRANSIT) SITE ACCESS & TRANSIT SERVICE IMPROVEMENTS 

Preferential Parking Preferential Parking 

Bicycle Lockers Bicycle Lockers 

New Transit Stops New Transit Stops 

More Frequent Transit Service 

Faster Transit Service 

FINANCIAL INCENTIVES & PARKING COSTS FINANCIAL INCENTIVES & PARKING COSTS 

Parking Cash-Out Parking Cash-Out 

Differential Parking Charges Differential Parking Charges 

Transit Incentives Transit Incentives 

SITE-SPECIFIC EMPLOYER SUPPORT PROGRAMS AREA-WIDE EMPLOYER SUPPORT PROGRAMS 

On-site Transportation Coordinator On-site Transportation Coordinator 

Ridematching Ridematching 

Outreach and Promotion to Employees Outreach and Promotion to Employees 

Outreach and Promotion to Employers 

ALTERNATIVE WORK SCHEDULES ALTERNATIVE WORK SCHEDULES 

Flex-time Flex-time 

Compressed Schedules Compressed Schedules 

Staggered Hours Staggered Hours 

Telework Telework 

EMISSIONS-RELATED INPUT SCREENS 

FLEET EMISSIONS INFORMATION (Optional) OTHER EMISSIONS-RELATED DATA (Optional) 

Inputs for Pre-Loaded MOBILE Factors Vehicle Fleet Mix

 Inputs for User-Supplied MOBILE Factors Affected Vehicle Speeds 

VMT Mix by Facility Type 

RESULTS SCREEN 

RESULTS 

Mode Shares & Changes 

Trip Changes 

VMT Changes 

Emission Reductions: 

HC (as VOCs) 

CO 

NOx 

PM 

CO2 

Air Toxics 

15

2.6 Can I save my inputs to use in another analysis? 

Saving Scenarios - To make repeated use of COMMUTER quicker and easier, you can 

save a complete set of analysis inputs and re-use them later as a template for evaluating 

other scenarios. This avoids having to type in complete data from scratch for each 

analysis, but still allows you to modify selected data to evaluate alternatives. 

After inputting data for a specific analysis case, save the information to a “scenario file” 

(indicated by a “.VME” file extension). First click on the “File” menu and select “Save 

Scenario.” This will bring up a dialog box that allows you to save the file to disk for later 

use. Click the arrow to the right of the “Save in” box to select the directory where you 

want to save the file, then type a file name for the scenario to be saved in the “File name” 

box, using the .VME suffix. (To make it easier to find and use your files, you may want 

to save the “.VME” scenario files to the same folder or directory where the application 

program was stored, e.g., C:\COMMUTER.) 

Loading Saved Scenarios - When you want to load and re-use a saved scenario file, click 

the “Load Scenario” item from the File menu. Then, select the directory and the specific 

scenario file you saved earlier to be loaded into the application. Re-using existing 

scenarios and making minor changes to their inputs is a more efficient way to create a 

series of related scenarios than typing in all the data for each scenario. 

Clearing Scenarios - If for some reason you have loaded a scenario or have typed in data 

for all the input cells and want to delete the data from all the input cells and start over, 

you can click the “Clear Scenario” item on the File menu. This initializes the program by 

erasing the data currently contained in the input cells if you want to start re-entering all 

new data without having to exit and reload COMMUTER. It does not delete saved 

scenario files from your hard disk. 

2.7 Can I use my own emission factors? 

COMMUTER has been supplied with 192 sets of MOBILE6.2 emission factors that 

encompass a range of input conditions throughout the country. Each of these supplied 

data sets contains emission factors for six calendar years: 2007, 2009, 2010, 2013, 2019, 

and 2021. Under general circumstances when COMMUTER is used as a screening 

model, selecting the set of pre-loaded emission factors that best matches your local 

conditions is adequate. However, if you want to use COMMUTER to produce emission 

reductions reflecting local conditions, such as for SIP or conformity purposes, you must 

use your own locally generated MOBILE6.2 emission factors to calculate emission 

reductions in COMMUTER. The steps for using your own emission factors are 

explained below. 

16

Step 1 - Create Properly Formatted Emission Factor Output File-Although you can 

specify your exact local input conditions, your MOBILE6.2 output emission factors 

must be generated in a specific format expected by COMMUTER. The sample 

MOBILE6.2 template input file M6SAMPLE.IN, which is provided with the model, 

identifies how specific commands in the MOBILE6.2 input file must be set to 

produce output emission factors in the COMMUTER-required format. In addition, it 

contains a series of 13 "Scenario" records that produce emission factors over a range 

of speeds expected by COMMUTER. These scenario records can be edited to reflect 

the altitude, calendar year, local ambient temperature, season of interest, and local 

fuels data. In addition, the user may specify other locality-specific data in the "Run 

Data" or "Scenario" sections, such as I/M programs, vehicle registration distributions, 

or alternative Tier 2 phase-in schedules. Speed data files for each scenario are 

provided with the model and should not be edited. 

In addition, the user must specify the "database output" option with the formats 

shown in the sample file. In addition, the user must specify calculation of particulates 

as well as air toxics, as shown in the sample file, and provide the fuel parameters and 

particulate emission factor inputs in each scenario record, as required by MOBILE6.2 

to calculate particulate and air toxics emissions. If these conventions are not 

followed, the resulting MOBILE6.2 model output will not work properly with 

COMMUTER. 

IMPORTANT: Once you’ve edited the 13 scenario records to 

reflect your own altitude, temperature, and season inputs, you can 

copy and paste this block of records to create emission factors for 

multiple calendar years. 

Once you have set up your MOBILE6.2 input file as described above and in 

accordance with the required database output options, run MOBILE6.2. You can 

name the MOBILE6.2 input and output files as you choose. 

Step 2 - Process MOBILE6.2 Output - Once you have run MOBILE6.2, an 

intermediate step is required to process MOBILE6.2 database-format output into the 

format expected by COMMUTER. You can run this step from inside the 

COMMUTER model using the "Process MOBILE6.2 Output" command from the 

"File" menu. This command will allow you to browse for and select a standard 

MOBILE6.2 database output file (.TB1) extension. It will then convert the data in 

this file into a text file suitable for import into COMMUTER, with a .TBZ extension. 

Note that corresponding toxics and PM MOBILE6.2 output files are also read (.TOX 

17

and .PM extensions, respectively), and a corresponding VMT file (.VMT) is also 

generated that contains VMT fractions by vehicle type and facility type. The model 

user must retain these files in the same directory as the .TB1 and .TBZ files and 

should not delete them. The routine to process MOBILE output may take a few 

minutes to run; this is normal. 

Step 3 - Activate User-Supplied Emission Factors Option - On the "Fleet Emissions 

Information" input screen in COMMUTER, you have the option of selecting 

"User-Supplied Emission Factors." Once you have selected this option and specified 

a calendar year, you will be reminded to Import User Emission Factors, as described 

below. It is important that the calendar year you have specified match one of the 

calendar years included in the .TBZ file you select. 

Step 4 - Import User Emission Factors - Once you have generated a .TBZ file, you 

can import this file into the COMMUTER model using the "Import User Emission 

Factors" command from the "File" menu. This command will allow you to browse 

for and select a .TBZ file. You may select any .TBZ file that you already have 

generated from MOBILE6.2 output, without re-running the "process MOBILE6.2 

output" routine described above. Importing the .TBZ file will take a few seconds; 

you will be notified when the import routine has been successfully completed. These 

emission factors will be saved within the COMMUTER model until you import a 

different set of either user-specified or default scenario emission factors. 

2.8 How do I view the results? 

Once you have provided all of the required inputs (or selected default values), 

COMMUTER will automatically calculate TCM travel impacts and, if you’ve entered 

emission factor inputs, emission reductions. To view the results, all you need to do is 

simply click either of the two command items on the Results menu. “View Travel 

Results” displays travel impacts only. “View Travel and Emission Results” shows both 

travel impacts and emission reductions (assuming you’ve entered emission factor inputs). 

You can then scroll down the tabular summary to see the calculated results. Key outputs 

include the following: 

•	 Baseline and final mode shares for each mode, including percent of trips


eliminated and change in mode share (final minus baseline);


•	 Percent of trips shifted from the peak to off-peak period; 

•	 Baseline and final peak, off-peak and daily VMT; 

18

•	 Baseline and final peak, off-peak and daily vehicle trips; and 

•	 Change in total daily emissions for each pollutant in tons per day and/or pounds 

per day. 

NOTE: If you did not enter all of the necessary input data, an 

“Incomplete or Inconsistent Input” message box will be displayed 

when the View Travel Results or View Travel and Emission Results 

buttons are clicked. The message box indicates which data must 

still be entered. If you click the OK button in the message box, the 

program will activate the first entry screen and cell for which 

missing or invalid data were detected. 

To return to an input screen after viewing the results calculated by COMMUTER, simply 

click the appropriate item in the Edit Inputs menu at the top of the application window. 

2.9 How do I print my data and results? 

For each scenario you evaluate, you can print both the detailed input data and the 

tabulated emission reductions. To do this, click the File menu. Then select “Print 

Inputs” from the drop-down menu to print a detailed listing of all program inputs. Select 

either “Print Travel Results” or “Print Travel and Emission Results” from the File menu 

to print a one-page output report showing travel impacts or travel impacts and emission 

reductions, respectively. 

Figure 4 shows the layout of a sample output report. General scenario information and 

the specific TCMs evaluated are listed at the top of the report. Included in these items are 

boxes that indicate whether you have supplied your own final mode shares and emission 

factors. Below these items, summaries of the combined mode share impacts and travel 

and emission reductions from baseline levels for all the TCMs selected are presented. As 

noted in the table headers, travel and emission reductions are shown as positive numbers. 

19

Figure 4 

Sa 

COMMUTER MODEL RESULTS mp 

SCENARIO INFORMATION 

Description

Scenario Filename

Emission Factor File 

Performing Agency

Analyst

Metropolitan Area 

Area Size 

Analysis Scope

Analysis Area/Site 

Total Employment 

le 

PROGRAMS EVALUATED Ou 

 Site Walk Access Improvements tp 

 Transit Service Improvements 

Financial Incentives ut 

 Employer Support Programs Re Alternative Work Schedules 

po 

 User-Supplied Final Mode Shares rt 

MODE SHARE IMPACTS TRAVEL IMPACTS (relative to affected employment) 

Mode Baseline Final %Change 

Drive Alone 

Carpool 

Vanpool 

Transit 

Bicycle 

Pedestrian 

Other 

No Trip 

Total 

Quantity Peak Off-Peak Total 

Baseline VMT 

Final VMT 

VMT Reduction 

% VMT Reduction 

Baseline Trips 

Final Trips 

Trip Reduction 

% Trip Reduction 

Shifted from Peak to Off-Peak 

EMISSION REDUCTIONS (positive values are decreases) 

lbs/day: 

Pollutant Peak Off-Peak Total 

HC 

CO 

NOx 

PM2.5 

Toxics 

Acetaldehyde 

Acrolein 

Benzene 

1, 3-Butadiene 

Formaldehyde 

MTBE 

CO2 

tons/day: 

Pollutant Peak Off-Peak Total 

HC 

CO 

NOx 

CO2 

20

CAUTION: The program allows you to set up a scenario and 

produce results for an individual TCM (as opposed to a 

combination of measures). However, summing the results for 

measures evaluated individually will not give you an accurate 

representation of the true impact of a combination of measures. 

2.10 Can I tell the model to remember where my files are stored? 

Depending on how you launch COMMUTER (see Section 2.2), your “default” directory 

(the directory pointed to when you open or save files) may not be the same as the 

directory that the model and scenario files are stored in. You can tell the model where to 

look for your scenario (and emission factor) files so you don’t have to click out of the 

“system” default directory (e.g., C:\My Documents) each time you want to open or save a 

scenario. 

To set your default or “working” directory when you’re running COMMUTER, click 

“Set Working Directory” from the File menu. The first time you do this, COMMUTER 

will report that the working directory is blank as shown below. 

This is normal. Simply click the “Yes” button. Another window, shown below, will be 

displayed that then allows you to enter the disk drive and directory path where you’ve 

installed COMMUTER (e.g., C:\COMMUTER). 

21

Once you have set the working directory, COMMUTER remembers that location and 

uses it each time you open or save scenario files or import your own emission factors, 

even if you exit and then re-run the model. 

2.11 What do I do when I’m finished? 

Before exiting COMMUTER, be sure you have saved the current inputs in a scenario file, 

as described above, if you plan to re-use them later. When you have completed your 

analysis session and want to exit COMMUTER, click “Exit Program” from the File 

menu. The application will then close and exit. 

22

3. GENERAL INPUT SCREENS


This and the following two sections guide you step-by-step through the data that must be 

provided in each of the input screens. This section covers the first three screens, which 

you use to input general information; Section 4 explains the five input screens that are 

specific to individual TCMs being analyzed; and Section 5 discusses the two screens you 

will use to enter information required to calculate emission reductions. Each subsection 

within these sections corresponds to one of the program’s ten input screens. These have 

been ordered in the sequence in which you would generally enter data for an analysis. To 

make it easier to find information on specific data inputs, fields have been noted in bold, 

underlined text. 

3.1 Scenario Information 

Scenario information describes the area you are analyzing and the broad types of 

commuter choice programs to be analyzed. Figure 5 displays the layout of the Scenario 

Information screen. Key data items are explained below. 

Metropolitan Area Size - This is where you define the size of the metropolitan area you 

are analyzing, using the following categories: 

� Large - more than 2,000,000 in population; 

� Medium - 750,000 to 2,000,000 in population; and 

� Small - less than 750,000 in population. 

Based on the area size you select, the program will retrieve default travel speeds. You 

have the option to override the default speeds in the “Edit Emissions Data” screen with 

values you obtain for your city. 

Analysis Scope - The actual analysis can apply to any geographic level. However, you 

must define the scope of your analysis as being area-wide (“1”) or site-specific (“2”). 

23

Figure 5


Scenario Information Input Screen


SCENARIO INFORMATION 

Field Data Notes 

Scenario Information 

Scenario Filename 

User EFs Filename 

Description 

Filename of scenario stored on disk 

User-supplied MOBILE emission factors (if used) 

Title to further identify the scenario (optional) 

General Information 

Performing Agency 

Address 

Analyst 

Metropolitan Area 

Metropolitan Area Size 

Name of your organization (optional)


Address of your organization (optional)


Your name (optional)


Name of city/area being modeled (optional)


1 = Large (Over 2 million) 2 = Medium (750,000


to 2 million) 3 = Small (Under 750,000)


Metropolitan Area Size is a required input. The program retrieves default freeway and arterial travel speeds for the 

area size input by the user. However, these defaults for Large, Medium and Small metropolitan areas may not be 

as accurate as locally-derived travel speed data. These default travel speeds can be overridden in the "Edit Other 

Emissions-Related Data" screen. 

Definition of Analysis Area 

Analysis Scope 

Analysis Area/Site 

Analysis Area Type 

1 = Area-Wide (Metropolitan Area, County, etc) 2 

= Site or Employer-Based 

Name of analysis area evaluated (optional) 

1 = CBD (Central Business District) 2 = Other 

High-Density Commercial 3 = Other 

The COMMUTER model can be used to evaluate commuter choice programs on both an urban area-wide and 

individual employer (or site-specific) basis. The Analysis Scope input controls whether the model calculates areawide or site-specific impacts of commuter choice programs. 

Employment in Analysis Area 

Office Employment 

Non-Office Employment 

Total Employment -

Refers to "traditional" professional office space 

employment 

Manufacturing, warehousing, retail, medical, 

educational, entertainment and other employmentgenerating land uses 

The COMMUTER model may generate abnormally large mode shifts under a regional or area-wide analysis 

scenario if realistic limits are not applied in estimating the affected employment input above. For site-specific 

analysis, enter the employment of the workplace being analyzed. For area-wide analysis, the user is encouraged to 

consult Section 3.1 of the COMMUTER Model User Manual for more detailed guidance on estimating affected 

employment inputs for region being modeled. 

Programs (Mark All Programs Being Analyzed with an "X") 

Includes preferential parking, improved access to 1. Site Walk Access Improvements transit 

Includes more frequent and/or faster transit 2. Transit Service Improvements service 

Includes parking costs, transit fare/pass 3. Financial Incentives subsidies, or other financial incentives 

Includes support programs for carpooling, 4. Employer Support Programs vanpooling, transit, and/or bicycling

Includes flex time, telecommuting, staggered work 5. Alternative Work Schedules hours, and/or compressed work weeks 

24

An area-wide analysis evaluates TCM programs for a geographic area such as traffic 

corridors, subareas (for example, the central business district), activity centers (for 

example, a large office park complex), or the entire metropolitan region. A site-specific 

analysis evaluates TCM programs applied only to a single business or employer location. 

This option can be used when considering either a single place of business for a given 

employer or a mixed use or multi-purpose place of business for a given employer or 

employers. If you are an individual employer using this model to evaluate a company 

employer support program, you should use the “site-specific” analysis. 

As discussed in Sections 4.3 and 4.4, you will later be asked for further data that are 

related to the scope you select. For example, if you specify “area-wide,” some screens 

will ask you to specify the percentage of employers in the area participating in the 

program. If “site-specific” is specified, this percentage will be assumed to be 100 

percent. (See Sections 4.3 and 4.4 for detailed instructions for inputting data for both 

area-wide and site-specific analysis.) 

Affected Employment in Analysis Area - The impact or applicability of various 

programs and strategies is affected by type of employees in an area, which COMMUTER 

defines according to the land use category of the employer. “Office” employees are those 

working in land use categories that include traditional professional office space. 

“Non-office” employees include those working in manufacturing, warehousing, retail, 

medical, educational, entertainment, and other employment-generating land use activities. 

You will be asked to enter both the number of office and non-office employees in the area 

or at the target site that can be affected by the TCM programs being modeled. “Affected” 

is the keyword in understanding what employment levels you should input here and 

depends on whether you are performing a site-specific or area-wide analysis, as explained 

below. 

Site-Specific Affected Employment - If you are performing a site-specific or “single 

employer” analysis (specified by choosing “2” for Analysis Scope), the employment 

levels you enter should be the total of all employees that are eligible for, or exposed to, 

any or all of the TCM programs you are evaluating. Most of the time, site-specific 

affected employment will be the total employment level at the site. In rare cases where 

employer support, financial incentive, or alternate work schedule programs being 

evaluated would only be made available to a portion of all employees, enter that portion 

as the affected employment. 

Area-Wide Affected Employment - In an area-wide analysis, affected employment should 

not be entered as the total employment in the area being considered. You must estimate 

that subset of the total area employment that will be potentially affected by any or all of 

the specific TCM programs you are evaluating. 

25

CAUTION: For area-wide analysis, you should not enter the total 

employment in the analysis area. You do not want to base the 

analysis on the total employment in the analysis area because 

COMMUTER will then generate unrealistically high results for 

regional scenarios. For example, the number of trips being shifted 

from one mode of travel to another if all employees for a given 

region are assumed to participate in a voluntary program would be 

too high. 

Steps to help you calculate the number of employees that can be affected by the TCM 

programs you are evaluating under an area-wide analysis are listed below. 

1.	 First, identify the portion of regional employers (and number of employees) that are 

currently participating in existing programs, and therefore should be excluded from 

the analysis. You can obtain the percentages of employers (by size and type) from the 

MPO responsible for transportation and emissions planning in the region. Using the 

total number of employees for a region is not realistic. 

2.	 Finally, determine that portion of employers of a specific size (based on their number 

of employees) that will be subjected to, or encouraged to implement, the voluntary 

programs being evaluated. This percentage will vary by MPO region and could 

include either office or non-office employers with 1,000, 500, 250, or 100 employees. 

3.	 Next, estimate the portion of employers of each type (office and non-office) who will 

agree to participate in any of the TCM programs you are evaluating, which will 

largely be voluntary in nature. This percentage will vary by MPO region and could 

include office employers only or a combination of office and non-office employers. 

The following example is provided to demonstrate how you should use this process to 

determine the employment levels you need to enter under an area-wide analysis. 

Assume total employees for Region X:	 1,000,000 employees 

1.	 Estimate portion of total employees currently 

participating in existing TCM programs:	 20% -200,000 employees 

800,000 employees 

2. Estimate portion of remaining employees by size of 

employer targeted by your voluntary programs, using 

26

employers of 500+ employees in this example: 

Office (500+ employers): 

Non-office (500+ employers): 

250,000 employees 

50,000 employees 

3. Determine portion of remaining employees based on 

estimated percentage of employers willing to 

participate in any of the modeled programs: 

(In this example we’ll assume 30% office and 

10% non-office employer participation) 

Office - 30% participation: 

Non-Office - 10% participation: 

75,000 employees 

5,000 employees 

Using this example, you would enter inputs of 75,000 and 5,000 employees for affected 

office and non-office employment, respectively. 

You should be careful in making assumptions about the number of affected employees in 

each region. Each region is likely to be significantly different based on the current 

participation in voluntary programs, employer and employee participation rates, and 

regional employment characteristics. 

As these steps and the example indicate, when inputting the “affected” employment under 

an area-wide analysis, you should supply estimates of the number of office and non-office 

employees that are eligible for participation in any of the specific TCM programs you are 

evaluating. 

NOTE: If you are evaluating a scenario that packages multiple 

programs (e.g., site access improvements, transit improvements, 

and financial incentives), individual “program” participation rates 

can also be specified in subsequent input screens for each program. 

You should not confuse these program-specific participation rates 

with the employer participation percentage in any program used to 

estimate affected employment inputs. The program-specific 

participation rates in subsequently discussed input screens provide 

you with a means to “weight” the participation of all affected 

employees within individual programs when analyzing scenarios 

that combine multiple programs. 

27

Programs - In this section, you simply check off which types of TCM strategies or 

programs are to be considered in the scenario being analyzed. There are five possible 

choices, described below. You simply mark (with an “X”) all of the programs being 

analyzed; you do not have to select only one. 

1. Site Walk Access Improvements - Includes preferential parking for employees 

using carpool and/or vanpool programs and improved access to transit systems. 

2. Transit Service Improvements - Includes more frequent and/or faster transit 

service. 

3. Financial Incentives - Includes any project or program that changes the out-ofpocket cost of alternative travel modes relative to automobile travel. Examples 

include transit fare/pass subsidies, parking costs, or other financial incentives. 

4. Employer Support Programs - Includes support programs for carpooling, 

vanpooling, transit, and/or bicycling that do not result in any changes in direct 

travel time or cost changes. For example, employers might provide information 

about ridesharing and transit opportunities, match employees with carpools or 

vanpools, and offer guaranteed ride home programs. 

5. Alternative Work Schedules - Includes flex time, telecommuting, staggered work 

hours, and/or compressed work weeks. 

NOTE: If you are planning to enter your own estimate of final mode 

shares as described in the Local Data inputs in Section 3.2, 

COMMUTER will ignore any TCM programs you check here. By 

inputting your own final mode shares, you are bypassing 

COMMUTER’s final mode share calculations that are based on 

TCM screen inputs. 

3.2 Local Data 

Once you have provided the general information on the scenario you are analyzing, you 

need to provide data on the existing travel behavior and characteristics of the area or site. 

Because travel characteristics such as mode shares (for example, transit users) and 

average travel distances can vary a great deal within a region, you should define separate 

geographic areas that have distinct and more or less homogenous characteristics for 

28

analysis. For example, you may wish to conduct separate analyses for the central 

business district (CBD) and for the non-CBD portions of a city. 

Baseline (i.e., existing) travel data for the region of interest are entered in the Local Data 

input screen, shown in Figure 6. Each of the data elements in this screen is discussed 

following Figure 6. 

29

Figure 6 


Local Data Input Screen


LOCAL DATA 

Baseline (Existing) 

Use Data 

Default Local Default 

Work-Trip Mode Shares Supply Final Mode Shares? 

Auto - Drive Alone


Auto - Carpool


Vanpool


Transit


Bicycle


Walk


Other


Total


78.2% 

12.1% 

0.5% 

4.9% 

0.4% 

3.0% 

0.8% 

0.0% 100.0% 

Work Trip Length (mi) 

Average person-trip length 

Average trip length -- vanpool 

Average trip length -- bicycle 

Average trip length -- walk 

12.2 

20.4 

2.9 

0.9 

Vehicle Occupancy 

Average Carpool Occupancy


Average Vanpool Occupancy


Length of Peak Period (hours) 

Percent of Work Trips in Peak Periods 

2.3 

7.2 

3.0 

61.4% 

Baseline mode share, trip length, average occupancy and peak period data representing local conditions are entered in this 

input screen. From these inputs and data entered in the "Mode Choice Model Coefficients" screen, the COMMUTER model 

internally calculates final mode shares and travel changes resulting from TCM programs selected. If you want to supply your 

own estimates of final mode shares (such as might be obtained from employee survey data), mark the box labeled "Supply Final 

Mode Shares" (with an "X"). When this option is selected, the COMMUTER model displays an additional series of input cells 

below the box where final mode share inputs can be entered. Remember, these final mode shares should reflect work-trip 

mode choice after implementation of the TCM programs you’re currently analyzing and override the mode share calculations 

made by the model. 

The peak period includes the morning and evening time periods when highways are most congested. These periods may be 

defined differently in different areas. For the default "percent of work trips in peak period" provided, the AM peak is defined as 

6:00 to 9:00 AM and the PM peak as 4:00 to 7:00 PM. The same peak period should be used for reporting percent of work trips 

in peak period and affected vehicle speeds (which are entered later in the "Other Emissions-Related Data" screen). 

"Length of peak period" refers to the length (in hours) of the AM or PM peak period. If the AM and PM peak periods are different 

lengths, this can be an average of the two lengths. 

"Percent of work trips in peak period" should also be reported as an average for the AM and PM peak periods combined. For 

example, assume there are 200,000 and 300,000 total vehicle trips in the AM and PM peak periods, respectively. If the number 

of work trips are 150,000 in the AM peak and 250,000 in the PM peak, then the percentage of work trips in peak period is 

(150,000 + 250,000) / (200,000 + 300,000) = 80%. 

Existing Mode Shares, Trip Length, and Occupancy - If you are conducting a sitespecific analysis, you may be able to obtain data on existing employee mode shares from 

employee surveys, if such surveys have been conducted. You can also enter local data on 

trip lengths and average vehicle occupancy for carpools and vanpools if such data are 

available. 

30

If you do not have specific data available, you should be able to obtain transportation data 

for the city, metropolitan area as a whole, or other area of analysis from the regional 

transportation planning agency. You should work with local or regional transportation 

planners to identify the most appropriate data for the analysis. 

If local data are not available, you may use the default parameters provided in the model. 

These are shown in Figure 6 under the “Defaults” column. You should indicate which 

default values to use by checking the appropriate box(es) on this screen. 

User-Supplied Final Mode Shares - If you are performing an analysis where you have 

estimates of “final” mode shares (after implementation of the TCMs being modeled), you 

can enter these final mode share estimates in the Local Data screen. Under most 

circumstances, you’ll want to let COMMUTER calculate final mode shares based on the 

inputs you supply in the TCM screens using the pivot-point methodology discussed in 

Section 1.5. There may be certain situations where you want to enter your own estimate 

of final mode shares, rather than using COMMUTER’s calculations. For example, when 

you are performing a site-specific analysis for a company, you may have employee 

survey data available that estimate how mode choice would change in response to a 

particular program or programs. 

For these situations, mark the “Supply Final Mode Shares?” box at the upper right of the 

Local Data input screen. When you do, a series of cells appears below this box, allowing 

you to enter final mode shares, reflecting changes from existing shares due to the TCM 

programs you’re modeling. 

For example, suppose under existing conditions that “Company A” work-trip mode 

shares were split at 80% Auto-Drive Alone and 20% Transit. Company A is considering 

a program in which employees are offered a cash incentive to ride the bus and, from an 

employee survey, determines that an additional 5% would accept the incentive and ride 

the bus. The final mode shares are thus split as 75% Auto-Drive Alone and 25% Transit. 

These values would be entered in the final mode share cells after you marked the “Supply 

Final Mode Shares?” box. 

NOTE: When you enter your own final mode shares in the Local 

Data input screen as explained above, any TCM programs that 

you’ve checked at the bottom of the Scenario Information screen 

and inputs you’ve entered in those TCM-specific screens are 

ignored. By entering your own final mode shares, you’re telling 

COMMUTER not to use the TCM inputs to calculate final mode 

shares. 

31

Under most circumstances, you won’t know what the final mode shares will be as a result 

of the TCM programs that you are analyzing. In these cases, leave the “Supply Final 

Mode Shares?” box blank and allow COMMUTER to calculate final mode share from the 

TCM program inputs you’ll enter in subsequent input screens. 

Length of Peak Period - The “peak period” includes the morning and evening time 

periods when highways are most congested. These periods may be defined differently in 

different areas. You should use the same peak period definition when reporting the 

percent of work trips in a peak period that you use when reporting baseline travel speeds 

(see below). You can obtain information on the peak period definition from 

transportation planning staff at your regional transportation planning agency. 

“Length of peak period” refers to the length (in hours) of the AM or PM peak period. If 

the AM and PM peak periods are different lengths, you should use the average of the two. 

Percent of Work Trips in Peak Periods - You need to enter the percent of trips during 

the peak periods that are work-related, averaging the totals for the AM and PM peak 

periods combined. For example, assume there are 200,000 and 300,000 total vehicle trips 

in the AM and PM peak periods, respectively. If the number of work trips are 150,000 in 

the AM peak and 250,000 in the PM peak, then the percentage of work trips in the peak 

period is calculated as follows: 

150 ,000 + 250 , 000 = 80% 200 ,000 + 300 , 000 

You should enter local or site-specific data if it is available, instead of relying on the 

default value. The default value provided is based on the national percentage of all work 

trips that occur in both the AM and PM peak periods. In this program, the default AM 

peak is defined as 6:00 to 9:00 AM and the default PM peak as 4:00 to 7:00 PM. 

3.3 Edit Coefficients 

This screen allows you to enter locally available values for mode-choice travel time and 

cost coefficients, rather than use the default values provided by the model. Figure 7 

illustrates the layout of the Edit Coefficients screen. 

Mode-choice coefficients are used within COMMUTER to compute changes in travel of 

each commute mode (e.g., drive-alone, carpool, transit, walk, etc.) under Site Access or 

Transit Improvement programs and Financial Incentive programs. These coefficients are 

used in transportation models referred to as “logit mode-choice” models to represent the 

willingness of commuters to use alternate modes of travel to driving alone when faced 

32

with changes in travel time or cost. (Please refer to the accompanying COMMUTER 

Model Procedures Manual for detailed information on how mode-choice coefficients are 

developed, tested and applied in transportation modeling.) 

The travel and emission impacts calculated by COMMUTER are highly sensitive to the 

values of these coefficients, especially the cost coefficients. It is strongly recommended 

that you use local coefficients for mode choice, if available. Coefficients have been 

estimated in many urban areas by the regional transportation planning agency (usually 

MPOs, Councils of Government, or Associations of Governments). Values of travel time 

and cost coefficients for many individual cities are incorporated into COMMUTER at the 

bottom of this input screen. The values of these mode-choice coefficients are based on 

the travel models currently used by regional transportation planning agencies. You are 

encouraged to contact your local transportation planning agency to ensure the values cited 

are up-to-date or to obtain coefficients for cities not listed in the table at the bottom of the 

input screen. 

If local mode choice model coefficients are not available for your city, you can use the 

default values provided by the model (which are based on the “Metropolitan Area Size” 

you specified in the Scenario Information screen; see Section 3.1). However, these 

defaults will not represent mode choice behavior as accurately as actual local data. 

33

Figure 7


Edit Coefficients Input Screen


MODE CHOICE MODEL COEFFICIENTS 

DEFAULTS BY AREA SIZE IVTT (min) OVTT (min) Cost (cents) 

Check

All Modes Walk Time 

Transit -- 

Wait 

Auto ­

Parking 

Transit ­

Fare 

All Areas -0.0253 -0.0473 -0.0466 -0.0056 -0.0040 

User-Specified 

Coefficients Used: Boston -0.0314 -0.0330 -0.0550 -0.0173 -0.0083 

Mode choice model coefficients are entered in this screen. The program retrieves default coefficients based on national 

average from numerous cities’ models. However, these defaults are typically not as accurate as city-specific coefficients 

developed for many communities across the country. City-specific coefficients for a number of cities based on a review of 

current literature and existing travel demand models are provided for use within the model and can be viewed by scrolling down 

below this help box. The user is encouraged to utilize these local coefficients for the specific city being modeled (if available) in 

lieu of the defaults by simply checking the box next to the appropriate city. The user is also encouraged to contact their local 

transportation planning agency to ensure the values cited are up-to-date or to obtain coefficients for cities not listed in these 

tables. 

When applying user-specified values, be aware that most models generally use input travel/wait time coefficients in MINUTES 

and cost-related coefficients in CENTS. Mode choice models such as the TDM model then internally convert the values of 

these coefficients to match the units of the travel/wait time or cost inputs. The COMMUTER model has also been programmed 

to apply a conversion factor to the Auto Parking and Transit Fare cost coefficients (in cents) when used with financial incentive 

inputs in units of DOLLARS per vehicle per day. When inputting your own coefficients, make sure the travel/wait time 

coefficients are in MINUTES and the cost-related coefficients are in CENTS. 

Note to previous COMMUTER users: In COMMUTER Version 2.0, metropolitan area size is no longer used to select the 

default mode choice coefficients. A review of recently developed coefficients found that these coefficients do not show a 

significant variation by area size. 

CITY-SPECIFIC DEFAULTS IVTT OVTT Cost 

Check City Year All Modes Walk Time 

Transit -- 

Wait 

Auto ­

Parking 

Transit ­

Fare 

Albuquerque 1992 -0.0209 -0.0219 -0.0978 -0.0031 -0.0031 

Atlanta 2002 -0.0256 -0.0639 -0.0256 -0.0031 -0.0013 

Baltimore 1993 -0.0300 -0.0750 -0.0750 -0.0043 -0.0043 

Boston 1991 -0.0314 -0.0330 -0.0550 -0.0173 -0.0083 

Chicago 1990 -0.0282 -0.0440 -0.0960 -0.0021 -0.0008 

Cleveland 1994 -0.0178 -0.0444 -0.0378 -0.0034 -0.0024 

Columbus 1999 -0.0213 -0.0640 -0.0465 -0.0016 -0.0016 

Dallas 1996 -0.0544 -0.0640 -0.0640 -0.0056 -0.0055 

Denver 1997 -0.0180 -0.0540 -0.0180 -0.0014 -0.0012 

Detroit 1996 -0.0512 -0.0186 -0.0186 -0.0041 -0.0041 

Houston 1985 -0.0220 -0.0568 -0.0568 -0.0154 -0.0061 

Los Angeles 1996 -0.0450 -0.1073 -0.0423 -0.0025 -0.0025 

Milwaukee 1991 -0.0157 -0.0412 -0.0412 -0.0045 -0.0045 

New York 1996 -0.0113 -0.0380 -0.0554 -0.0004 -0.0004 

Philadelphia 1986 -0.0391 -0.0316 -0.0511 -0.0026 -0.0012 

Phoenix 1991 -0.0167 -0.0206 -0.0304 -0.0053 -0.0053 

Portland 1994 -0.0394 -0.0646 -0.0397 -0.0135 -0.0135 

Reno 1991 -0.0275 -0.0550 -0.0550 -0.0167 -0.0067 

Sacramento 2001 -0.0250 -0.0380 -0.0380 -0.0026 -0.0026 

San Diego 1995 -0.0250 -0.0500 -0.0250 -0.0069 -0.0026 

San Francisco 1990 -0.0333 -0.0931 -0.0523 -0.0021 -0.0021 

San Juan 1990 -0.0366 -0.0717 -0.0752 -0.0066 -0.0066 

Santa Cruz 1990 -0.0163 -0.0325 -0.0325 -0.0045 -0.0036 

Seattle 1990 -0.0176 -0.0206 -0.0155 -0.0024 -0.0024 

Tucson 2000 -0.0178 -0.0400 -0.0200 -0.0018 -0.0018 

Washington D.C. 1994 -0.0300 -0.0750 -0.0750 -0.0043 -0.0043 

34

4. TCM-SPECIFIC DATA


This section discusses the input screens that are used to enter TCM-specific data for each 

of five different types of programs, with each program having its own input screen. As 

explained in Section 2, programs can be analyzed individually or in combination.* At this 

stage, you can edit any of the programs checked under “Programs Analyzed” on the 

“Scenario Information” screen. (Remember, however, that if you did not select a 

program from the Scenario Information screen, you will not have access to the data entry 

screen for that program.) 

4.1 Site Access and Transit Service Improvement Programs 

This section describes the Site Access and Transit Service Improvement program inputs. 

Figure 8 shows the single input screen used for these programs. 

Site Access Improvements 

Site access improvements include such things as preferential parking policies for carpools 

and vanpools or improvements to the work site or area that make access to transit easier. 

For example, parking spaces in close proximity to both office building locations and 

transit station/transit center locations could be provided for ease of access and reduced 

travel times for carpool and vanpool vehicles. These programs also include improved 

pedestrian and bicycle infrastructure at transit locations to encourage transit usage. Along 

with preferential parking spaces, infrastructure improvements could include secure 

lockers and showers for pedestrians and bicyclists and improved access to transit facilities 

from the adjacent roadway system. 

Walk-Access Time - You will need to specify the change in “walk access time,” which is 

the time required to walk from the parking space or transit stop to the work site. A 

decrease in walk access time for any particular travel mode is represented as a negative 

value. 

* As noted in Section 2, however, you will not obtain accurate results by analyzing individual measures and 

then summing the results. Measures that may be implemented together should be analyzed together. 

35 
Figure 8 


Site Access & Transit Improvements Input Screen


SITE ACCESS & TRANSIT SERVICE IMPROVEMENTS 

I. Site Access Improvements 

Change in 

Walk Access 

Mode: Time (min) 

Drive Alone 

Carpool 

Vanpool 

Transit 

Bicycle 

Pedestrian 

Employer Participation Rate: 

"Change in Walk Access Time" represents the difference in walking time associated with travel to or from the workplace 

as a result of worksite access changes. Walking time includes the time taken to walk from a parking lot or a bus stop to 

the actual worksite. Walk access time can be affected through policies such as preferential parking for carpools and 

vanpools or through improvements to the worksite or area which make access to transit easier. A decrease in walk 

access time for any particular mode should be entered as a negative value. 

"Employer participation rate" refers to the percent of employers in the analysis area implementing the walk access 

improvements. (This option is not necessary for site-specific analysis because the "participation rate" is 100%.) 

II. Transit Service Improvements 

IIa. More Frequent Service 

Change in avg. headway (min) 

Employment Served (% of area) 

IIb. Faster Service 

Change in route travel time (min) 

Employment Served (% of area) 

Transit Operating Data 

Increase in daily VMT by Transit 

Vehicles 

Average speed of affected transit 

vehicles (mph) 

Default average speed 14.8 

Check here to use default transit 

speed 

"Change in average headway" refers to the average change in frequency of service for transit service to the employment 

center or analysis area. An increase in service frequency is entered as a negative number. For example, if peak period 

transit service frequency increases from 20-minute to 15-minute intervals, the change in average headway would be 

entered as "-5.0". 

"Change in route travel time" refers to the average change in total route travel time for all transit service to the area. A 

decrease in travel time is entered as a negative number. For example, if new express bus service decreases the overall 

route travel time by 5 minutes, this would be entered as "-5.0". 

"Employment served" refers to the percent of employment in the analysis area which is served by the improved transit 

service. (This option is not available for site-specific analysis). 

"Increase in daily VMT by transit vehicles" refers to the additional transit vehicle-miles of travel as a result of the 

improved transit service. Refer to Section 4.1 of the COMMUTER Model User Manual for guidance on how to calculate 

this parameter. 

36

Employer Participation Rate - If you specified an area-wide analysis scope, you will 

also need to specify the percent of employers in the analysis area implementing the walkaccess improvements. 

Remember, as discussed in Section 3.1, that there are two types of participation rates you 

need to consider in setting up the inputs to COMMUTER. The first type is used in 

estimating the affected employment inputs and refers to participation in any of the TCM 

programs being modeled. The second type, the individual program participation rates, 

are actual model inputs, and are used to further restrict the “eligibility” of all affected 

employment to individual programs, such as Site Access Improvement programs. Thus, 

in an area-wide analysis assuming 100,000 affected employees, a 15% Employer 

Participation Rate for Site Access Improvement programs instructs COMMUTER that 

15,000 employees (100,000 × 15%) are eligible or affected by site access improvement 

strategies. (Note that the model assumes a proportional ratio of employers to employees 

in determining affected employment for individual programs.) 

The employer participation rate is not used in site-specific analysis because it is assumed 

to be 100%. 

Transit Service Improvements 

Transit service improvements may include providing more frequent bus or shuttle service 

to work sites, as well as providing faster transit service through express routes or 

operational improvements. These improvements may also include implementing new 

route services resulting from the transit planning process. 

If you are analyzing improvements that lead to more frequent service, you will need to 

enter the “Change in Average Headway.” This refers to the average change in the 

frequency of transit service to the employment center or analysis area. An increase in 

service frequency is entered as a negative number. For example, if peak period transit 

service frequency increases from every 20 minutes to every 15 minutes, the change in 

average headway would be represented as -5.0 minutes. 

“Employment Served” refers to the percent of employment in the analysis area that is 

served by the improved transit service. As with the Employment Participation Rate input 

for Site Access Improvement programs, Employment Served should reflect the fraction of 

all affected employment that are exposed to the transit improvements. As an example, 

expanding transit service along a single network corridor would affect only the fraction of 

employment served by this transit corridor. Again, you do not need to enter this input if 

you are conducting a site-specific analysis. 

37

If you are evaluating faster service improvements, you will need to enter the “Change in 

Route Travel Time.” This refers to the average change in the time required to travel the 

total route for all transit service to the area. A decrease in travel time is represented as a 

negative number. For example, if new express bus service decreases the overall route 

travel time by 5 minutes, this would be represented as -5.0 minutes. 

If transit service improvements are implemented, the change in daily transit vehiclemiles as a result of increased service must also be considered. For this, you will need to 

estimate the following items: 

� The number of additional daily bus-trips on each route, for routes on which 

service is increased; and 

� The total round-trip route length for each route on which service is increased. 

You should be able to obtain information on route-mileage increases from the local 

transit agency or you can develop estimates from operating plans for the proposed transit 

service. Estimates of daily mileage increases should take into consideration the distance 

traveled to and from the storage/maintenance facility to the beginning/end of the route. 

In addition, an average travel speed for the affected transit service should be estimated. 

This can be done by dividing the total length of each affected route by the time taken to 

complete the route. 

If transit service improvements are implemented, the change in daily transit vehicle-miles 

as a result of increased service must also be considered. This requires estimating the 

following items: 

� The number of additional daily bus-trips on each route, for routes on which 

service is increased; and 

� The total round-trip route length for each route on which service is increased. 

Information on route-mileage increases can be obtained from the local transit agency or 

can be estimated from operating plans for the proposed transit service. Estimates of daily 

mileage increases should take into consideration the distance traveled to and from the 

storage/maintenance facility to the beginning/end of the route. 

In addition, an average travel speed for the affected transit service should be estimated. 

This can be done by dividing the total length of each affected route by the time taken to 

complete the route. 

38

4.2 Financial Incentive and Parking Cost Programs 

Financial incentives include any policies that affect how much it costs to travel via a 

particular mode. Some examples of financial incentives are listed below. 

� Increased parking charges, especially for single-occupant vehicles. 

� Reduced parking fees for carpools and vanpools. 

� Transit subsidies such as free monthly passes. 

� Parking cash-out programs. 

The Financial Incentive and Parking Cost program input screen is shown in Figure 9. A 

decrease in cost (i.e., an incentive) is entered as a negative number. Changes in parking 

cost are entered on a per-vehicle basis. Changes in other fare costs and other financial 

costs are entered based on the change in cost per person per day (i.e., round trip transit 

fare). 

Figure 9


Financial Incentives Input Screen


FINANCIAL INCENTIVES AND PARKING COSTS 

Change In Daily Cost: 

Other 

Financial Total Change 

Parking Cost Fare Cost ($/ Cost ($/ ($/ 

Mode: ($/vehicle) person/RT) person/RT) person/RT) 

Drive Alone $ -

Carpool $ -

Vanpool $ -

Transit $ -

Bicycle $ -

Pedestrian $ -

Employer 

Participation Rate: 

"Financial incentives and parking costs" may include higher parking charges for single-occupant vehicles, reduced 

parking fees for carpools or vanpools, transit subsidies such as free monthly passes, or other financial incentives for 

specific modes. A decrease in cost is entered as a negative number. For example, provision of a transit pass valued 

at $30 a month would be entered as a change in fare cost of -$1.50 ($30 / 20 days). The cost change inputs are 

entered on a daily basis. 

"Employer participation rate" refers to the percent of employers in the analysis area offering these incentives to their 

employees. (This option is not required for site-specific analysis because the "participation rate" is 100%.) 

39

As in other screens, “Employer Participation Rate” refers to the fraction of all affected 

employees being offered financial incentives on a percent-of-employers basis. Like the 

other program-specific “employer participation rate” inputs, COMMUTER applies the 

proportion of participating employers to determine the fraction of all affected employees 

being offered financial incentives. It is not used for site-specific analysis. 

Two examples are provided below to illustrate how the financial costs should be 

calculated and entered. 

Sample Calculations for Financial Incentives and Parking Cost Programs: 

� If parking costs are increased by $2.00 per day for all types of vehicles, you 

would enter +$2.00 for Auto-Drive Alone, Carpool, and Vanpool. (The model 

will convert the costs per vehicle to the costs per person by dividing by the 

assumed average vehicle occupancy as identified in “Local Data.”) 

� If a transit pass worth $30 per month is provided, you would enter a change in 

fare cost of -$1.50 ($30 divided by 20 days per month). 

Note that you enter these cost inputs in dollars per vehicle per day. COMMUTER 

internally converts the Parking Cost and Transit Fare mode-choice coefficients that you 

entered in units of cents in the “Edit Coefficients” screen into dollar units before 

combining them with the cost inputs entered in this screen in the mode share calculations. 

Parking Cash-Out Programs - Parking cash-out programs are modeled in this input screen 

by treating the cash-out payment as a “subsidy” for use of eligible alternative modes. For 

example, if the cash value of the parking subsidy were $60 per month or $2 per day, a 

current Single Occupant Vehicle (SOV) user would see no difference in his/her cost to 

drive (park), but the transit user would suddenly find it $2 per day cheaper to use transit. 

The same logic applies to all modes that are eligible alternatives, i.e., bike, walk, or 

ridesharing (if there is no problem with the cash-out recipient still parking at the site as a 

carpooler/vanpooler). In this example, you would enter -$2 in the “Transit” row and 

“Parking Cost” column. 

So to handle cash-out programs in COMMUTER, you enter nothing for the SOV mode 

parking cost, and enter a subsidy for each of the eligible alternative modes. Note that in 

the rideshare case, each passenger receives the full value of the subsidy, unlike where you 

give a parking discount to carpools and the savings is split among the number of 

occupants. 

40

4.3 Site-Specific Employer Support Programs 

There are a number of strategies that employers can use that reduce the number of people 

commuting to work in single-occupancy vehicles (SOVs), but do not result in measurable 

changes in the time or cost of traveling to work. Research suggests that such “soft” 

incentives or support programs can change travel behavior by providing encouragement 

to use other modes of travel, informing travelers of alternatives, or removing 

impediments. Examples of this type of strategy include selling transit passes at the work 

site, providing rideshare matches, marketing and promoting alternative modes, providing 

a guaranteed ride home program, forming and supporting a vanpool, and providing 

preferential parking for carpools. (Note that these types of programs also apply for an 

area-wide analysis, discussed in Section 4.4.) 

Figure 10 shows the input screen for site-specific analysis of employer support programs. 

As shown in the figure, the first thing you need to do is specify the entry format, which 

refers to the type of data you will be entering. 

For a site-based analysis, it is recommended that you specify existing and proposed 

program levels. These refer to the general level of effort spent on the program (which 

affects its effectiveness) and are explained below, along with the codes used for data 

entry. They are defined separately for carpooling, vanpooling, transit, and bicycle 

commuting. 

As an alternative, you can specify the expected mode share increase. This expected 

increase in each mode of travel is added to the baseline mode share that was specified in 

the input data. 

CAUTION: You should not use this alternative entry option unless 

you have good data indicating that a proposed program will lead 

to a likely mode share increase. If you do specify a mode share 

increase, you should document existing support programs and the 

programs to be implemented, along with survey or other data that 

were used to estimate the mode share increase. 

41

Figure 10 


Site-Specific Employer Support Programs Input Screen


EMPLOYER SUPPORT PROGRAMS FOR ALTERNATIVE MODES


SITE-SPECIFIC ANALYSIS


Entry Format (check one only): 

Specify Program Level 

Specify Mode Share Increase 

Specify Program Level: 

"Program Level" and "Mode Share Increase" input options are mutually 

exclusive. You enter input data for either one or the other based on which 

Entry Format box you check to the left. See the help box below for an 

explanation of each input. 

Program Existing New 

Carpool 

Vanpool 

Transit 

Bicycle 

Specify Mode Share Increase: 

Program Existing Increase New 

Carpool 0.0% 0.0% 

Vanpool 0.0% 0.0% 

Transit 0.0% 0.0% 

Bicycle 0.0% 0.0% 

"Employer Support Programs" include programs such as provision for an on-site transportation coordinator, ridematching, 

transit information, and other actions aside from time and cost incentives which encourage employees to utilize alternative 

modes. Two entry options are available for site-specific analysis: 

(1) Specify existing and new program levels for Carpool, Vanpool, Transit, and Bicycle program support. A program level 

of "0" represents no program. Program levels of "1" through "4" indicate varying levels of effort for the programs. These 

program levels are described in Section 4.3 of the COMMUTER Model User Manual. 

(2) Specify an expected mode share increase for each mode. This increase is added to the baseline mode share as 

specified in the input data. 

IMPORTANT: Entry option (2) should only be utilized if the user has evidence, such as survey data, suggesting a likely 

mode share increase as a result of proposed programs. If a mode share increase is specified, the user should document 

existing support programs and programs to be implemented, along with survey or other data indicating the basis for the 

mode share increase estimates. 

Definition of Program Levels 

The impact of employer support programs and strategies varies depending on the level of 

effort expended on the program. The level of program effort is a particularly important 

data input because it defines what is actually meant by, for example, a “carpool support” 

program. The program level can vary from 0 to 4, with 0 representing no program and 4 

representing a program of maximum effort. (These program level definitions will also 

apply for area-wide analyses, as discussed in Section 4.4.) The following program level 

descriptions are not requirements for each level, but are intended as suggested guidelines 

to help you assign a level designation to the support activities you are trying to model. 

42

Note that preferential parking or direct financial incentives to employees offered as part 

of a support program should be captured on the Site Access and Transit Service 

Improvement input screen, and the Financial Incentives and Parking Costs input screen, 

respectively. They should not be considered in the determination of program support 

level. 

Carpool Support Programs 

Level 0 - no program 

Level 1 - includes carpool information activities (tied in with area-wide matching) 

and a quarter-time transportation coordinator. 

Level 2 - includes an in-house carpool matching service and/or personalized 

carpool candidate get-togethers (including information activities) and a quartertime transportation coordinator. 

Level 3 - includes in-house carpool matching and information services plus 

preferential (reserved, inside, and/or especially convenient) parking for carpools, a 

policy of flexible work schedules* to accommodate carpools, and a half-time 

transportation coordinator. 

Level 4 - includes in-house carpool matching and information services plus 

preferential parking for carpools, flexible work schedules, and a full-time 

transportation coordinator. 

Vanpool Support Programs 

Level 0 - no program 

Level 1 - includes vanpool information activities (tied in with area-wide vanpool 

matching and/or third-part vanpool programs), plus a quarter-time 

transportation coordinator. 

Level 2 - includes in-house vanpool matching services and/or personalized vanpool 

candidate get-togethers, and non-monetary vanpool development, plus a 

quarter-time transportation coordinator and a policy of flexible work 

schedules. 

* Flexible work schedules as defined under these support programs refers to providing latitude to employees 

to accommodate slight variations in arrival/departure to participate in these programs. This differs from a 

formal Flex-Time policy, which is defined and discussed later in Section 4.5. 

43 
Level 3 - includes in-house vanpool matching services; vanpool development and 

operating assistance, including financial assistance, such as vanpool 

purchase loan guarantees, consolidated purchase of insurance, and a 

startup subsidy (generally, at least two forms of such financial assistance 

should be included); and additional services such as van washing and 

preferential (reserved, inside, and/or especially convenient) parking for 

vanpools, plus a half-time transportation coordinator. 

Level 4 - includes in-house vanpool matching services; vanpool development and 

operating assistance, including major financial assistance, such as 

employer purchase of vans with favorable leaseback (or alternative 

continuing subsidy, such as free maintenance, free insurance, and/or 

direct subsidy to keep vanpool fares low) in addition to startup subsidy; 

several additional incentives such as van washing, preferential parking for 

vanpools, guaranteed ride home, and a full-time transportation 

coordinator and/or personalized vanpool candidate get-togethers. 

Transit Support Programs 

Level 0 - no program 

Level 1 - includes a transit information center plus a quarter-time transportation 

coordinator. 

Level 2 - includes a transit information center and a policy of work hours 

flexibility to accommodate transit schedules/delays, plus a quarter-time 

transportation coordinator. 

Level 3 - includes a transit information center and a policy of work hours 

flexibility, on-site transit pass sales, plus a half-time transportation 

coordinator. 

Level 4 - includes a transit information center and a policy of work hours 

flexibility, on-site transit pass sales, guaranteed ride home, and a 

full-time transportation coordinator. 

Bicycle Support Programs 

Level 0 - no program 

Level 1 - providing on-site bicycle parking (racks or lockers). 

44

Level 2 - providing bicycle parking (racks or lockers) and shower facilities. 

Level 3 - providing secure bicycle parking (storage lockers or indoor storage) and 

shower facilities, in conjunction with local infrastructure conducive to 

bicycling. This includes the presence of (a) off-street bike paths, (b) onstreet bike lanes, and/or (c) local streets with light traffic by which 

cyclists can access the workplace. 

Level 4 - providing parking, shower, and infrastructure conditions as for Level 3, 

and also sponsoring workplace promotional activities. These activities 

should include promoting bicycle commuting, identifying the availability 

and location of parking and shower facilities, and providing local bicycle 

route maps, along with other activities to encourage bicycle commuting. 

Some employer support programs may have combinations of characteristics different than 

those shown here. In this case, you should choose the program level that most closely 

represents the actual program being implemented. 

If there is no program level that you feel most closely represents the combination 

program being offered, you can specify “combinations” of program levels by running the 

program for an area-wide rather than site-specific analysis. For example, if a carpool 

program includes all the elements of a Level 3 program except for flexible work 

schedules, you may want to model this program as halfway between Level 2 and Level 3 

in terms of effectiveness. You can do this by setting the analysis scope to “Area-Wide” 

and specifying that 50 percent of employers have a Level 2 program and 50 percent have 

a Level 3 program. Note that if you set the employer participation rate at 100 percent for 

every program being tested, the area-wide and site-specific analyses will give identical 

results. 

4.4 Area-Wide Employer Support Programs 

The discussion in Section 4.3 of the types of employer support programs that may be 

offered also applies here. Although different input formats are used for site-specific and 

area-wide employer support programs, the data elements themselves are similar. 

Figure 11 shows the input screen for area-wide analysis of employer support programs. 

45

Figure 11


Area-Wide Employer Support Programs Input Screen


EMPLOYER SUPPORT PROGRAMS FOR ALTERNATIVE MODES 

AREA-WIDE ANALYSIS 

Percent of Employers Participating -- Existing 

Program Level 

Program None 1 2 3 4 Total 

Carpool 100% 100% 

Vanpool 100% 100% 

Transit 100% 100% 

Bicycle 100% 100% 

Percent of Employers Participating -- New 

Program Level 

Program None 1 2 3 4 Total 

Carpool 100% 100% 

Vanpool 100% 100% 

Transit 100% 100% 

Bicycle 100% 100% 

"Employer Support Programs" include programs such as provision of an on-site transportation coordinator, 

ridematching, transit information, and other actions aside from time and cost incentives which encourage employees to 

utilize alternative modes. 

For an area-wide analysis, the analyst should specify both existing and new (expected) participation rates (percent of 

employers participating) by program level for each mode. Program levels of "1" through "4" indicate varying levels of 

effort for the programs which are described in Section 4.4 of the COMMUTER Model User Manual. 

You should use the definitions of support program levels given in Section 4.3 for areawide analyses also. Be sure to read these definitions before proceeding. 

For area-wide analysis of employer support programs, you must specify the percent of 

employers participating in each of the program levels and modes. For each mode 

(carpool, vanpool, transit, and bicycle), you need to enter the percent of employers in the 

area participating at each program level. The sum of Levels 0 through 4 for each mode 

should equal 100%. Employers who are not participating in any program would be 

included in the “Level 0” program level. Participation rates should be specified for both 

the base case (existing conditions) and the proposed program levels being evaluated. 

4.5 Alternative Work Schedule Programs 

This class of commuter-related TCM strategies is aimed at reducing how often commute 

trips are made or shifting the timing of the trip out of the peak hour. For example, flextime and staggered work hour strategies have the effect of merely shifting commute travel 

to a less-congested time period. These strategies will not affect the number of overall 

46

trips or the amount of VMT, but they will change the distribution of trips, VMT, and 

emissions between the peak and off-peak time periods. They may also affect overall 

emissions slightly by affecting the average speed in the peak and off-peak periods. 

Definitions of the various work schedule programs and their likely impacts are discussed 

later in this section. 

Figure 12 shows the input screen for entering information on alternative work schedules 

and telecommuting programs. As shown, you will first need to choose an entry format 

option, as explained below: 

� Eligibility Rate - This indicates the percent of all employees in the analysis 

system*

 who are offered the program. The model then applies an assumed 

participation rate to the total number of employees that are eligible. Note that the 

employees eligible for each alternative work schedule and those not eligible for 

any strategy must sum to 100 percent. In other words, only one alternative work 

schedule strategy may be offered to an employee at a time. This simplifying 

assumption is used in the manual and spreadsheet model because employees are 

unlikely to combine more than one alternative work strategy at a time (for 

example, those employees working a compressed work week are unlikely to be 

allowed to telecommute on regularly scheduled work days). This parameter 

relates mainly to the logic of applying this strategy to different employment 

segments. For example, manufacturing or retail employees are not reasonable 

candidates for participation in telecommuting programs. You should consider the 

characteristics of the employment base you are analyzing when determining the 

value to use for this parameter. 

� Participation Rate - As an alternative, you can specify existing and expected 

actual participation rates for each program. If you do specify the participation 

rates, you should document the existing support programs and the programs to be 

implemented, along with the survey or other data that formed the basis for the 

participation rate estimates. 

Alternative Work Schedules are more commonly implemented by employers as an 

employee benefit or workplace efficiency measure, rather than as a mode shift strategy. 

As such, the proportion of employees that might adopt these schedules is highly 

dependent on how and why the employer is implementing the program. The default 

proportions using the "eligibility rate" option are currently set to 22 percent for Flexible 

Work Hours, Staggered Work Hours, and 4/40 Compressed Work Weeks, and to 11 

percent for 9/80 Compressed Work Weeks. These figures reflect voluntary adoption of 

alternative work schedules if made available and optional. The user can change the 

* For an area-wide analysis, this will be the percent in the area-wide employment base; for a sitespecific (single employer) analysis, it will be the percent of employees within the firm. 

47 
proportion of employees who would shift to each schedule to reflect local knowledge of 

such programs. For example, if a given employer or set of employers decides to require 

staggered hours to addressed localized congestion or compressed work weeks to reduce 

overall operating costs, the proportion of employees shifting schedules could be 

considerably higher. 

Figure 12 


Alternative Work Schedules Input Screen


ALTERNATIVE WORK SCHEDULES 

Use Data 

Default Local Default 

Alternative Work Schedule Parameters 

Telecommute: Avg. Days/Week 

Flex Time/Staggered Hours: Percent of trips


shifted from peak period


Participation Entry Format (check one only): 

Specify Eligibility for Participation 

Specify Before/After Participation Rates 

A. Eligibility for Participation 

1.5 

% Eligible 

Program Existing New 

Flex Time 

Compressed 4/40 

Compressed 9/80 

Staggered Hours 

Telecommute 

Not Eligible 100% 100% 

Total 100% 100% 

B. Participation Rates 

% Participating 

Program Existing New 

Flex Time 

Compressed 4/40 

Compressed 9/80 

Staggered Hours 

Telecommute 

Not Participating 100% 100% 

Total 100% 100% 

"Alternative Work Schedules" include the option to allow employees to utilize flex time, compressed work weeks, staggered work hours, or 

telecommuting. Flex time and staggered hours will have the effect of shifting some trips outside of the peak period, while compressed 

work weeks and telecommuting will have the effect of eliminating some work trips. Two program entry options are available: 

(1) The user can specify the percentage of employees eligible for each program. Both existing and new levels of eligibility should be 

specified. 

(2) The user can specify existing and expected participation rates for each program. 

To accomodate instances where employees are eligible for, or participate in multiple programs, the model allows the user to enter rates 

that exceed 100% when summed across all alternative programs. The model then internally normalizes the rates before using them in 

the travel calculations. Section 4.5 of the COMMUTER Model User Manual presents an example for this situtation. 

IMPORTANT: Entry option (2) is preferred if the user can obtain data indicating a likely participation rate as a result of proposed 

programs. If participation rates are specified, the employer/analyst should document existing support programs and programs to be 

implemented, along with survey or other data indicating the basis for the participation rate estimates. If the user does not have survey 

data indicating likely participation rates or another strong basis for estimating expected local participation rates, entry option (1) should be 

used. 

48

Definition of Alternative Work Schedule Strategies 

Flex-Time - In this policy, employees can adjust their work schedule (based on when they 

arrive at and depart from the work site) in order to travel during the off-peak hours, when 

there should be less traffic congestion. COMMUTER assumes a formal Flex-Time 

policy rather than flexible work schedules. Flexible work schedules are seen as simply 

allowing employees who would carpool or take transit to arrive or leave with slight 

variations in order to be compatible with the pool/bus schedule. In contrast, a Flex-Time 

policy involves formally moving the time of arrival or departure to a set of consistent 

work hours that are different from the employer’s official hours. This type of policy may 

actually detract from employees’ incentive to carpool or take transit as a means of 

avoiding traffic congestion. The only assumed effect of this strategy is to shift the time 

of the trips, no vehicle trips are eliminated. 

Staggered Work Hours - Under this strategy, employers establish different starting times 

for groups of employees in order to avoid having the entire workforce arrive or leave at 

the same time. Some work sites have a large number of employees arriving within a very 

narrow time period, so staggering starting hours can help reduce localized traffic 

problems. This strategy is also assumed to affect only the timing of the trips, not the 

number of vehicle trips. 

Compressed Work Week - Under this strategy, employees are allowed to reduce the 

number of work trips made by working longer hours on fewer days per week. Options 

include the 4/40 schedule where 40 hours are worked in 4 days with the fifth day off and 

the 9/80 schedule where 80 hours are worked in 9 days with the tenth day off. 

COMMUTER assumes that the 4/40 schedule eliminates one round-trip a week (1/5 of a 

daily trip) and that the 9/80 schedule eliminates one round-trip every two weeks (1/10 of 

a daily trip) for each participating employee. 

Telecommuting - This strategy involves allowing employees to work off-site, usually at 

home via telecommunications linkups, one or more days per week. Telecommuting thus 

reduces the demand for travel to the workplace. This is accounted for in COMMUTER 

by simply removing person trips, along with the equivalent number of vehicle trips, from 

the total amount of travel. (A more sophisticated analysis would consider how some of 

the commute trips might be replaced by non-work travel.) 

49

5. EMISSIONS-RELATED INPUT SCREENS


In the final two input screens, you will supply the information that COMMUTER needs 

to calculate emission reductions. (If you are only interested in using COMMUTER to 

compute travel impacts, you don’t need to enter any input information these two screens.) 

To make this easier, a large matrix of MOBILE6.2 emission factors was generated for a 

series of local conditions and provided with the program. (A total of 192 different sets of 

emission factors are provided with COMMUTER.) To use these factors, all that you need 

to do is supply a simple set of vehicle fleet characteristics, and COMMUTER will then 

look up the appropriate set of MOBILE6.2 factors and use them to calculate emission 

reductions from the TCM programs being evaluated. Thus, you do not have to supply 

detailed, locally generated MOBILE6.2 emission factors. 

If you are an experienced MOBILE6.2 user, however, and want to use emission factors 

that exactly match your local conditions, you can optionally direct COMMUTER to 

import and apply your locally generated factors. (Refer to Section 2.7 for step-by-step 

details on generating and properly importing your own MOBILE6.2 emission factors into 

COMMUTER.) 

5.1 Fleet Emissions Information 

In the first emissions-related input screen, you will provide the data needed for the 

program to select the appropriate set of pre-loaded MOBILE6.2 emission factors or 

activate the User-Supplied Emission Factors” option if you want to use your own locally 

generated MOBILE6.2 factors. 

Figure 13 shows the layout of this screen. If you want to use the pre-loaded emission 

factors contained in COMMUTER, follow the input requirements under “Using PreLoaded Factors.” To use your own factors, see “Using Locally Generated Factors.” 

Using Pre-Loaded Factors - To use pre-loaded factors, you must select from the available 

fleet characteristic options in the MOBILE Scenario section at the top of the screen that 

best match your local conditions. Once you've specified all of the fleet characteristics or 

changed any of these characteristics, you will be reminded to import the scenario-specific 

emission factors using the "Import Default Emission Factors" command on the "File" 

menu. You do not need to re-import the default emission factors if you only change the 

calendar year of analysis, as each default emission factor file contains factors for all six 

calendar years available. (Leave the “User-Supplied Emission Factors” and “Calendar 

Year of User EFs” cells toward the bottom of the screen blank.) 

50

Figure 13a 


Fleet Emissions Information Input Screen (p. 1)


FLEET EMISSIONS INFORMATION 

Field Data Notes 

MOBILE Scenario Inputs 

Enter either 2007, 2009, 2010, 2013, 2019, or 2021 

S = Summer, W = Winter 

1 = Mild, 2 = Moderate, 3 = Severe 

0 (zero) = none, 1 = Basic I/M, 2 = Enhanced I/M, 3 = OBD Only 

C = Conventional, R = RFG 

1, 2, 3, 4, or 5 (based on state - see below) 

Calendar Year of Analysis 

Season 

Climate Type 

I/M Program Type 

Fuel Type 

PADD 

The "MOBILE Scenario" inputs are used by the program to select a specific set of MOBILE6.2 emission factors from a series of 

stored tables that best represent local conditions and emission control programs being modeled. These inputs are familiar to 

MOBILE6.2 users. Further clarification of these inputs for users less familiar with the MOBILE6.2 emission factor model is 

provided below. Once the user has entered all scenario inputs, or changed an input, he or she must import the scenario 

emission factors using the "Import Default Emission Factors" command from the File menu. 

Calendar Year - Because new vehicle emission levels continue to decrease with the introduction of each model year, current and 

future vehicle fleet emissions will depend on the calendar year being analyzed. 

Season - This input affects the temperature range for which emissions are modeled (emissions characteristics of vehicles vary 

depending upon the temperature range in which the vehicle is being operated.) The choice of season may depend upon which 

pollutants are of greatest interest. Since ozone is typically a summer problem and carbon monoxide (CO) is typically a winter 

problem, summer should generally be used if ozone is of primary interest, while winter should be used if reducing CO is of 

primary interest. The seasonal importance of other pollutants may vary regionally. 

Climate Type - This input is used on conjunction with the "season" input to determine default temperature ranges for the model. 

Choose the climate type (1 = mild, 2 = moderate, 3 = severe) that most closely matches the average daily minimum and 

maximum temperatures in your area (in deg F) as specified below:

 Summer - Mild: min 55/max 75


 Summer - Moderate: min 65/max 85


 Summer - Severe: min 75/max 95


 Winter - Mild: min 52/max 72


 Winter - Moderate: min 32/max 52


 Winter - Severe: min 12/max 32


If the user is interested, monthly normal temperatures for 250 cities can be looked up through the National Climatic Data Center,


http://www.ncdc.noaa.gov/oa/ncdc.html. 


I/M Program Type - The type of Inspection and Maintenance (I/M) program, if any, being operated. Basic I/M refers to a program


where a simple "no-load" idle or 2500 RPM test is performed. Enhanced I/M represents programs in which a loaded IM240 or 


ASM test are run on a dynamometer. OBD Only represents programs in which vehicles are not subject to an annual or biennial


inspection. but instead emissions malfunctions are identified by a vehicle’s on-board diagnostics (OBD) system.


Fuel Type - Under the 1990 amendments to the Clean Air Act, certain areas of the country must use reformulated gasoline (RFG) 


beginning in 1995. This input allows the user to specify whether RFG is being used. A map and list of counties in which RFG is 


required is provided on the EPA’s web site, http://www.epa.gov/OMSWWW/rfg/whereyoulive.htm.


PADD - (Petroleum Administration for Defense District) - PADD's were delineated during World War II to facilitate oil allocation.


The characteristics of refined fuels, and therefore the emissions characteristics of vehicles, vary generally by PADD. The most 


significant effect is on emissions of air toxics. Select the appropriate PADD (1 – 5) based on your analysis state:


 1 - East Coast: Connecticut, Delaware, District of Columbia, Florida, Georgia, Maine, Maryland, Massachusetts, New 

Hampshire, New Jersey, New York, North Carolina, Pennsylvania, Rhode Island, South Carolina, Vermont, Virginia, West 

Virginia. 

2 - Midwest: Illinois, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, Missouri, Nebraska, North Dakota, South Dakota, 

Ohio, Oklahoma, Tennessee, Wisconsin.

 3 - Gulf Coast: Alabama, Arkansas, Louisiana, Mississippi, New Mexico, Texas. 

4 - Rocky Mountain: Colorado, Idaho, Montana, Utah, Wyoming.

 5 - West Coast: Alaska, Arizona, California, Hawaii, Nevada, Oregon, Washington. 

For a map of PADDs, see: http://www.eia.doe.gov/pub/oil_gas/petroleum/analysis_publications/oil_market_basics/paddmap.htm. 

51

Figure 13b 

Fleet Emissions Information Input Screen (p. 2) 

User-Supplied MOBILE Emission Factors

 Mark the box to the left (with an "X") to compute emission reductions 

User-Supplied Emission Factors using alternate MOBILE6.2 emissions factors instead of the

 pre-loaded factors already contained in the COMMUTER model 

Calendar Year of User EFs Select the calendar year of the user-supplied emission factors 

The COMMUTER model has been designed to use pre-loaded MOBILE6.2 emission factors for a defined range of input 


conditions or a set of user-supplied emission factors for specific local conditions. Before user-supplied emission factors can be 


used, the user must load these factors into the model using a two-step process:


1) MOBILE6.2 database format output must be processed, using the "Process MOBILE Output" command from the File menu. 


This routine requests the user to select a MOBILE6.2 output file (.TB1), and then produces a text file with the extension ".TBZ,"


that is formatted for import into the COMMUTER Model.


2) The .TBZ data file must be imported, using the "Import User Emission Factors" command from the File menu. The user can 


choose a different .TBZ file without having to process MOBILE output every time. 


The "Process MOBILE Output" command requires the availability of a MOBILE6.2 output file in database format (.TB1 file 


extension), along with corresponding toxics (.TOX) and particulate (.PM) output files that have the same base file name as the 


.TB1 file. The resulting .TBZ file can be stored with the COMMUTER Model for future use, and the .TB1, .TOX, and .PM files 


deleted or moved if desired. The database output options must be specified as shown in the sample MOBILE6.2 input file 


provided and described in Section 5 of the User Manual. The "Calendar Year of User EFs" input identifies the specific calendar


year factors from the set of user-supplied factors. The calendar year can be any year between 1960 and 2050, but must match 


one of the available calendar years in the user-provided MOBILE6.2 output files. (These output files may include a maximum of


six calendar year scenarios.)


Each of these “pre-loaded” fleet characteristics inputs is explained below. 

•	 Calendar Year - Since vehicle fleet emission levels change as new technology 

improvements are introduced on newer cars, the calendar year that represents the 

analysis scenario must be entered. 

You can choose either 2007, 2009, 2010, 2013, 2019, or 2021. If you are 

interested in an analysis year between two of those years, the model should be 

run for both of the surrounding years (for example, if you are interested in 2008, 

you should run analyses for both 2007 and 2009). You will then need to 

interpolate the resulting travel and emission impacts to represent impacts in the 

year of interest. 

When you choose the year, you should keep in mind the time period when the 

TCM programs being modeled will actually be implemented. For example, in 

evaluating improved levels of transit service, it may take a couple of years to 

implement the service improvements. 

•	 Season - Vehicle emissions vary depending upon the ambient temperature and, 

in some areas, fuel controls are imposed only in certain seasons. You therefore 

need to enter the season for the analysis of interest, selecting either "S" (summer) 

or "W" (winter). If you are an air quality planner, you will generally select 

52

summer when evaluating ozone-related emission reductions (including VOC and 

NOx), and winter for carbon monoxide evaluations. The seasonal importance of 

other pollutants may vary regionally. 

•	 Climate Type - This input is used in conjunction with the "season" input to 

determine temperature ranges for the model. You should choose the climate type 

(1 = mild, 2 = moderate, 3 = severe) that most closely matches the average daily 

minimum and maximum temperatures in your area (in degrees Fahrenheit), in 

either summer or winter depending upon your analysis season: 

- Summer - Mild (S, 1): min 55/max 75


- Summer - Moderate (S, 2): min 65/max 85


- Summer - Severe (S, 3): min 75/max 95


- Winter - Mild (W, 1): min 52/max 72


- Winter - Moderate (W, 2): min 32/max 52


- Winter - Severe (W, 3): min 12/max 32


You may, if you choose, look up monthly normal temperatures for your city 

through the National Climatic Data Center, 

http://www.ncdc.noaa.gov/oa/ncdc.html. Data for 250 cities are provided at no cost 

on this web site. In most areas, summer temperatures for July and winter 

temperatures for January (when temperatures are at their highest and lowest) should 

be used. 

•	 I/M Program Type - The type of Inspection and Maintenance (I/M) program, if 

any, being operated in your area will affect fleet emissions. If you do not know 

what type of I/M program is in place in your area, your state department of 

environmental protection or department of motor vehicles should be able to tell 

you. The following I/M program options are available: 

- None (0) - No I/M program exists in your area. 

- Basic I/M (1) - A program where a simple "no-load" idle or 2500 RPM test is 

performed along with a visual inspection; 

- Enhanced I/M (2) - A program in which a loaded IM240 or ASM test are run 

on a chassis dynamometer in conjunction with a visual and functional 

emission control system inspection; 

- OBD Only (3) - A program in which vehicles are not subject to an annual or 

biennial inspection, but instead emissions malfunctions are identified by a 

vehicle's on-board diagnostics (OBD) system. 

•	 Fuel Type - Under the 1990 amendments to the Clean Air Act, certain areas of 

the country must use reformulated gasoline (RFG) beginning in 1995. This input 

allows the user to specify whether RFG is being used. A map and list of counties 

53

in which RFG is required is provided on the EPA’s web site, 

http://www.epa.gov/OMSWWW/rfg/whereyoulive.htm. 

•	 PADD - (Petroleum Administration for Defense District) - PADDs were 

delineated during World War II to facilitate oil allocation. The characteristics of 

refined fuels, and therefore the emissions characteristics of vehicles, vary 

generally by PADD. The most significant effect is on emissions of air toxics. 

Select the appropriate PADD (1 - 5) based on your analysis state:

 1 - East Coast: Connecticut, Delaware, District of Columbia, Florida, Georgia, 

Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, 

North Carolina, Pennsylvania, Rhode Island, South Carolina, Vermont, 

Virginia, West Virginia.

 2 - Midwest: Illinois, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, 

Missouri, Nebraska, North Dakota, South Dakota, Ohio, Oklahoma, 

Tennessee, Wisconsin.

 3 - Gulf Coast: Alabama, Arkansas, Louisiana, Mississippi, New Mexico, 

Texas.

 4 - Rocky Mountain: Colorado, Idaho, Montana, Utah, Wyoming.

 5 - West Coast: Alaska, Arizona, California, Hawaii, Nevada, Oregon, 

Washington. 

For a map of PADDs, see: 

http://www.eia.doe.gov/pub/oil_gas/petroleum/analysis_publications/oil_market_ba 

sics/paddmap.htm. 

Using Locally Generated Factors - Once you have successfully imported your own 

locally generated MOBILE6.2 emission factors into COMMUTER as described in 

Section 2.7, you can direct COMMUTER to apply them in the emission reduction 

calculations by marking the “User-Supplied Emission Factors” box (with an “X”) toward 

the bottom of the screen. Once you activate this option, you must then enter the specific 

calendar year of the emission factors you’ve imported in the “Calendar Year of User EFs” 

input cell. (This input is used to select a specific calendar year from a set of factors 

you’ve imported that may encompass multiple calendar years. Even if you’ve only 

imported emission factors for a single year, you must enter it into this input cell.) 

54

NOTE: When you activate the “User-Supplied Emission Factors” 

option, any entries you may have made in the “MOBILE Scenario 

Inputs” cells at the top of the screen are ignored. In addition, the 

vehicle fleet mix and VMT mix by facility type that you've specified 

in your locally generated emissions factors file is automatically 

loaded into the appropriate cells in the “Other Emissions-Related 

Data” screen that follows. 

5.2 Other Emissions-Related Data 

In this final input screen, you will provide additional emission-related inputs that 

COMMUTER will then use in conjunction with the MOBILE6.2 emission factors 

discussed in Section 5.1 to calculate “before TCM” (i.e., existing) and “after TCM” daily 

emissions for the vehicle fleet. It will then determine the resulting emission reductions 

from the TCMs being evaluated. 

Figure 14 shows the Other Emissions-Related Data input screen. Each of the inputs you 

will be required to enter is described below. 

Vehicle Fleet VMT Mix - The light-duty vehicle fleet is composed of nine different 

classes of vehicles, which are listed on the screen. The VMT mix for the vehicle fleet 

refers to the percent of the total travel (VMT) that is driven by each of the nine vehicle 

classes. The emission factors in MOBILE6.2 are based on vehicle class. COMMUTER 

will calculate emissions for the entire vehicle fleet (referred to as the fleet composite 

emissions) based on the percentage of VMT in each vehicle class, by weighing the 

emission factors together according to the fleet mix input. 

If known, you should supply local data on fleet mix for the analysis area in the “Local” 

column. Only the light-duty vehicle mix (vehicles <8,500 lb.) is required, since the 

strategies analyzed by COMMUTER are not intended to affect travel by heavy-duty 

vehicles (trucks). You may enter the vehicle mix either as a percentage of all light-duty 

vehicles (in which case the total should sum to 100%), or as a percentage of all vehicles 

including heavy-duty vehicles. If the total you enter is less than 100%, COMMUTER 

will assume that you have selected the second alternative and will normalize the 

percentages to 100%, to represent the fractions of light-duty vehicles. 

55

Figure 14 


Other Emissions-Related Data Input Screen


OTHER EMISSIONS-RELATED DATA 

Use Data 

Default Local Default Explanatory Notes 

Vehicle Fleet VMT Mix 

LDGV - Light-Duty Gas Vehicles 

LDGT1 - Light-Duty Gas Trucks 1 

LDGT2 - Light-Duty Gas Trucks 2 

LDGT3 - Light-Duty Gas Trucks 3 

LDGT4 - Light-Duty Gas Trucks 4 

LDDV - Light-Duty Diesel Vehicles 

LDDT12 - Light-Duty Diesel Trucks 1 & 2 

LDDT34 - Light-Duty Diesel Trucks 3 & 4 

MC - Motorcycles 

TOTAL 

Affected Vehicle Speed (mph) 

Peak Period Average Speed - Freeways 

Off-Peak Period Average Speed - Freeways 

Peak Period Average Speed - Arterials 

Off-Peak Period Average Speed - Arterials 

Percent of VMT by Facility Type 

Freeway


Arterial


Local Road


Ramp


TOTAL (must add to 100%)


#N/A 

#N/A 

#N/A 

#N/A 

#N/A 

#N/A 

#N/A 

#N/A 

#N/A 

0.0% #N/A 

Percentages of total VMT by vehicle type 

Passenger Cars 

0-6,000 lbs. GVWR, 0-3,750 lbs. LVW 

0-6,000 lbs. GVWR, 3,750-3,750 lbs. LVW 

6,000-8,500 lbs. GVWR, 0-5,750 lbs. ALVW 

6,000-8,500 lbs. GVWR, over 5,750 lbs. ALVW 

Passenger Cars 

0-6,000 lbs. GVWR 

6,000-8,500 lbs. GVWR 

Gasoline 

If not 100%, model will normalize 

Average speed (mph) of TCM-affected trips 

50.5 

56.4 

24.2 

26.0 

34.2% 

49.8% 

13.1% 

3.0% 

0.0% 100.0% 

Vehicle Fleet VMT Mix 

MOBILE6 generates emission factors for each of the nine different vehicle classes listed. Fleet "composite" emission factors 

are then calculated by weighting these emission factors by the percentage of travel (i.e., VMT) in each vehicle class. The 

default VMT mixes provided by this program are MOBILE6 national default values. These defaults are calendar year specific; 

you must enter a calendar year under the Fleet Emissions Information screen before the defaults will appear. If you 

are using user-supplied emission factors, the emissions factor import routine will automatically generate and look up a VMT 

mix from your MOBILE6 output file. If you are using default emission factors and do not enter local data for a VMT mix, the 

model will use the default MOBILE6 VMT mix. 

Only the light-duty vehicle mix (vehicles <8,500 lb.) is required, since the strategies analyzed by COMMUTER are not intended 

to affect travel by heavy-duty vehicles (trucks). The user may specify the VMT mix either as a percentage of all vehicles, or as 

a percentage of light-duty vehicles. If the total of the light-duty vehicle categories entered is less than 100%, the model will 

assume that the user is entering the percentage of all vehicles (including heavy-duty) and will normalize these percentages to 

total 100% (representing the fraction of light-duty vehicles). 

Note: GVWR = Gross Vehicle Weight Rating; LVW = Loaded Vehicle Weight; ALVW = Adjusted Loaded Vehicle Weight. 

Affected Vehicle Speed 

Vehicle emissions vary with speed. The values entered here should represent regional network average speeds during the 

peak and off-peak periods. Default values supplied are based upon HPMS (Highway Performance Monitoring System) 

averages compiled by urban area size. 

Percent of VMT by Facility Type 

Vehicle emissions vary by roadway facility type because of the different traffic operating characteristics on different facilities 

(e.g., freeway travel typically involves less starting and stopping than travel on other roads). MOBILE6 defines four facility 

types: freeways, arterials, local roads, and freeway ramps. If user-supplied emission factors are provided, the facility mix will 

be read from the user-supplied MOBILE output files and the user does not need to specify the mix. If default emissions factors 

provided with the COMMUTER model are used, you may either specify a local facility mix or use the default mix that is 

provided with the model. 

56

If local data are not available, you can check the boxes in the “Use Default” column to 

use the national default fleet mixes obtained from MOBILE6.2. Note that the default 

fleet mixes vary by calendar year. 

As indicated in Section 5.1, if you are using your own locally generated emission factors, 

the VMT mix from your MOBILE6.2 emission factor file is automatically loaded into 

these input cells. 

Affected Vehicle Speeds - The values you enter here should represent existing average 

vehicle speeds in your region. You should be able to obtain data on average travel speeds 

from transportation planning staff at the regional transportation planning agency. Even if 

you are running a site-specific analysis, enter speeds that represent averages for your 

urban region. 

You will need these values for both peak and off-peak periods, and for freeways as well 

as arterials.* Peak period travel speed should be the average of travel speeds in the AM 

and PM peak periods, if these values differ. 

CAUTION: Do not specify travel speeds at a geographic area 

smaller than the county level. Even if you are performing a sitespecific analysis, the speed inputs should reflect average regional 

network travel speeds that employees at the site experience driving 

to and from work. 

You may also choose to use default travel speeds, shown in Table 2, if local data from the 

regional MPO are not available. These default values have been estimated from national 

highway data. Travel speeds will vary depending on metropolitan area size, since larger 

areas tend to be more congested. 

* In most cases, the MPO for a given region is responsible for both transportation planning and emissions 

analysis. The MPO maintains local data related to travel demand, speed, and emissions inventories for 

regional planning purposes. These data are typically available to member agencies (counties, cities, transit 

operators) and businesses. Metropolitan-level emissions inventory data sets generally provide local data on 

travel speeds by peak and off-peak periods that are generated from the travel demand modeling process and 

used in regional air quality conformity analysis. 

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Table 2


Default Speeds (mph) by Area Size


Period 

Highway 

Type Large 

Urban Area Size 

Medium Small 

Peak Freeway 40.2 46.8 50.5 

Arterial 22.6 23.2 24.2 

Off-Peak Freeway 49.0 54.7 56.4 

Arterial 25.1 25.5 26.0 

VMT by Facility Type 

Vehicle emissions vary by roadway facility type because of the different traffic operating 

characteristics on different facilities (e.g., freeway travel typically involves less starting 

and stopping than travel on other roads). MOBILE6 defines four facility types: freeways, 

arterials, local roads, and freeway ramps. If user-supplied emission factors are provided, 

the facility mix will be read from the user-supplied MOBILE output files and you do not 

need to specify the mix. If the default emissions factors provided with the COMMUTER 

model are used, you may either specify a local facility mix or use the default mix that is 

provided with the model. 

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6. REFERENCES


1.	 J. R. Kuzmyak, et. al., "Procedures Manual for Estimating Emission Reductions 

from Voluntary Measure and Commuter Choice Incentive Programs", prepared for 

the U.S. Environmental Protection Agency," Draft Final Report, September 19, 

1999. 

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