TMODEL^TM OVERVIEW

INTRODUCTION

TModel Corporation provides three levels of information concerning TMODEL. The color brochure contains the briefest look, presenting glimpses of the features and power of the integrated system of program modules which comprise TMODEL. In fact, many of the graphic features presented in the color brochure have been enhanced and new features have been added after the brochure was printed.

This document provides an intermediate level overview, discussing topics such as cost, features, ease of use, training, customer support, calibration aids, post assignment analysis, intersection modeling and interactive graphics. It also discusses some of the features and advantages of NCAP which is included in the TMODEL system of programs.

The most complete level of information is the TMODEL User's Manual which describes the purposes, functions and assumptions of the program. The User's Manual exists both as a three-ring binder edition and as a disk file and can be read from the TMODEL Menu including keyword search capabilities. Many updates continue to be made to TMODEL. These are all described in a document called TMREADME.DOC which is available from the TMODEL Main Menu and for downloading. Before purchasing the TMODEL System, you can try the sample version of the program, a fully functioning, up-to-date, but limited size version of TMODEL.

WHAT IS TMODEL?

TMODEL is a package of tools used to construct and analyze multi-modal transportation planning models, also known as a 4-step models. It is usually used to build a peak-hour model because it accounts for street and intersection (link and node) congestion in the development of travel times. This notion is best applied to peak hour rather than average daily traffic volumes. After a modeler enters land use or socioeconomic data (population and employment) and network (street and intersection) data, the model distributes or allocates an appropriate number of trips from each zone, or land use area, to each other zone. It then assigns those trips to the streets of the network based on the least cost (time and/or distance) paths.

TMODEL is a mathematical model. It allows the user to select operating formulas and coefficients, to insert land use and street network data, and then to calibrate [iteratively adjust these coefficients and data] until the model produces traffic volumes that closely approximate known counts for the network. Using a calibrated model, the final data and parameters, a planner or engineer can then insert projected land uses and/ or transportation network system improvements in order to test for resulting traffic flows and problem facilities.

The TMODEL system of programs also includes NCAP, the iNtersection Capacity Analysis Package. It can function as a stand-alone program or use TMODEL turn movement assignments directly as input data for analyzing intersection operation. NCAP contains six methods of intersection capacity analysis; the SR209 (1985 Highway Capacity Manual) methods for UNSIGNALIZED [1] 3 leg (T) and [2] 4 leg, SIGNALIZED [3] planning and [4] operational analysis as well as the TRC 212 methods for SIGNALIZED [5] planning and [6] operations and design. NCAP is in the process of being updated to match the 1994 Highway Capacity Manual and to add the all-way stop control method. NCAP follows the SR209 Manual methods as closely or more closely than any other intersection capacity analysis program including the HCS software.

For the modeler, TMODEL is fully menu-driven, providing a logical path through modeling operations, as much as that is possible. Furthermore, it operates using all ASCII files, fully described, with the exception of the vine files, the street name files and layer files that are stored in binary formats for economy of space. The user may, therefore, intervene in many of the processes should he or she need or wish to do so, using spreadsheet, database, editor or other data manipulation tools.

Finally, after generating a distribution and assignment, TMODEL offers full analysis and reporting capabilities through tables, graphs, and mapping capabilities.

COST

The attached list shows the price of the TMODEL package. The price includes A) one year of software maintenance and updates, B) membership in the TMODEL Users Group which publishes a newsletter containing articles concerning aspects of TMODEL use, and C) free telephone support using toll-free 800 numbers in North America. Free support is also provided via fax, Internet, and email. We are proud to be known for excellent support!

While TMODEL is one of the lower-priced full featured transportation planning model packages available, we will openly tell you that purchase cost is but one part of the overall cost of developing a model for an area. The major costs are in the time it takes to do data collection, data input and verification, calibration runs and alternative scenario ("what if") analyses.

Programs, such as TMODEL, which provide efficient methods for successful and accurate completion of these tasks, may easily save more in labor costs than their original purchase costs. Because we at TModel Corporation are modelers as well as programmers, we are constantly making the program more powerful yet easier to use and, at the same time, answer more of the questions that are important to your and our modeling efforts.

Another part of the cost is in training and ease of use. There are multiple levels of participation in the modeling process, such as:

The physical accomplishment of levels [1] and [3] and the computer runs portion of [4] can be learned with only a few days of training and can then be done by various level employees. The interpretation portion of level [4] requires a person capable of interpreting network volumes and turn counts, whether produced by counts, hand-generated assignments or computer assignments.

Level [2], calibration, requires a more specialized expertise. This person (or group of people) must understand the modeling process, the adoption of the proper assumptions, the features and options of the program, the interdependence between land use and transportation and other modeling issues. This requires extensive training over a significant period of time. This, however, is not training specific to the use of TMODEL, but general training in transportation planning and modeling.

Calibration requires an appropriate blend of immersion in many details while maintaining sight of the big picture. Because of this, we recommend involvement of more than one person in developing a model for an area. This means having one individual responsible for the detail work who makes regular detailed progress reports to others who can help maintain the larger view. In this way problems may be discovered before they become expensive in terms of work which must be redone.

Because a significant portion of the cost and requirements for expertise are associated with calibration, an agency needing a model should consider who ought to do the calibration. Sometimes the expertise or potential expertise exists in-house and agencies can take on the entire task themselves. In other cases, they may wish to contract out that portion of the task to skilled people and then arrange to be trained to do their own alternative testing and analysis.

BENEFITS

In spite of the costs, it is time to recall how great the benefits are of having an operating transportation model. Once you have a calibrated model, it is extremely easy to test the effects of changes on your system. Examples of its use are:

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• Land use changes - how they affect traffic
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• Network changes - the effects of improving the streets or intersections or of restricting streets temporarily for construction on other parts of the system
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• Land use restrictions based on desired levels of performance of the existing or envisioned transportation network
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• Travel characteristics - changes in trip generation rates, use of other modes, auto occupancy or other travel demand management strategies
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• System statistics - any statistics involving data entered into link and node files in user defined formulas may be calculated and the results mapped.
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• Analysis tools - alternatives can be easily compared with tools for deriving and plotting emissions, level of service, and other measures.

There are many opportunities for uses of a traffic simulation model. Modeling helps you avoid the much greater costs of over- or under-building the future street network.

TRAINING

TMODEL Corporation holds training courses at our offices and other locations. In addition to having regularly scheduled seminars, we collect the names of people who desire training and schedule a class whenever we have enough students at that location.

These workshops are hands-on. They are structured to take an individual with some understanding of traffic modeling methods and goals from beginner status with TMODEL to being able to develop a straightforward model. The course provides a framework for understanding TMODEL methods and a thorough introduction to its capabilities. The emphases are on data entry, data verification, calibration techniques and alternative scenario testing.

Advanced workshops or individual assistance are available upon request. We have a classroom at our Vashon, Washington office equipped with computers and a high speed plotter which can be used when you want specialized assistance developing your model.

FEATURES

There are times when a broad brush overview is all that is needed and default methods are available for this. At other times, however, the user wants to be able to tailor methods for his or her purposes. TMODEL is designed to be extremely flexible to suit these wishes. Perhaps the most difficult thing now is to select the appropriate options from all those available.

As part of this flexibility, all the file structures are open to the user and are described in the appendix of the manual. If the user has their own method of trip generation or any other activity accomplished by the program, they may develop or modify files in a spreadsheet or with their own program. However, he must then output the file in the TMODEL format for use by the program.

To fully describe the features of TMODEL would be to rewrite the manual. Rather, this section will describe some generalities and notions of the more important features of the program.

MODEL SIZE

This is an area of flexibility. TMODEL software will accommodate over 1,000 zones. The nominal limits for nodes and links are 2,500 and 15,000 respectively. Number of zones, nodes and links can be traded off, although not one for one. All data is kept within memory during all operations for maximum speed and responsiveness.

INTERSECTION MODELING

Historically, regional models and the microcomputer models based on them have modeled the transportation network as a set of connected links. To account for the delays caused by the intersections, the operational capacity and speed of the links had to be adjusted to some "planning capacity" and "planning speed" which would hopefully produce reasonable "operational" travel times. This causes an inherent problem. The modeler needed to assign capacities and speeds to each link along a particular route to account for intersection delays of various magnitudes. Since there is no operational definition for these capacities or speeds, they can only be obtained by seeing whether they then cause assignment of appropriate volumes. The capacity constraint function and capacities are based, therefore, on a circular argument and probably appropriate only for calibration conditions. One should then question whether future scenario volumes would have any meaning given those skewed capacity and speed definitions. The results are called into further question when used for speed dependent analysis such as LOS or air quality.

Since the inception of TMODEL, we have included the intersections when computing and analyzing travel times. In most situations, intersections rather than streets are typically the constraining factor on traffic flow. Accordingly, the TMODEL program allows for an intersection capacity description, use of intersection volume-to-capacity ratio (V/C) constraint functions and the use of dynamic turn penalty functions.

Through these techniques and functions, the user can describe an appropriate operational link capacity along the route. He can then define separate intersection capacity and turn penalty functions to the intersections, based on their operational descriptions. The benefits of this accrue, not only when travel times are more appropriately attributed to their causes, but also when the entire route is changed through addition of a lane or deletion of parking etc. These changes can then be applied through operational descriptions rather than guessed at, based on whatever method was used to derive "planning capacities" and "planning speeds."

With the philosophy of using true or engineering speeds and capacities comes the responsibility of using representative link and node delay functions. TMODEL uses a variation of the Bureau of Public Roads (BPR) function for determining congested link travel time. This function has been enhanced to allow a jointed equation that gives a more realistic travel time as the volume approaches capacity. Node delay functions operate in a similar manner with a jointed function representing the delay impacts of volume approaching the capacity. In combination, these tools allow the modeler to use engineering capacities and speeds to arrive at representative travel volumes as well as representative travel times. These are very important when modeling air quality and level-of-service.

New coming features allow conic or hyperbolic functions and cost factors applied to time and distance to better describe route choice and distribution.

INTERACTIVE GRAPHICS

The TMODEL Network Graphic Editor (NGE) is one of the features which makes TMODEL an extremely efficient tool for traffic modeling. The NGE is a mouse-controlled data entry tool, editor and reporter. It is straightforward, easy to learn, and very fast and smart in its functions. The following feature sections will familiarize you with some of the more "hands on" operations of TMODEL to provide you with a glimpse of our thorough and pragmatic approach toward modeling operations.

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• CLICK on a feature with the mouse to edit, examine or display it. It no longer is necessary to identify an intersection by its node number or a link by its node end numbers referring back to some hand drawn map containing the key to these numbers. This was always a source of error in network building and maintenance. Now simply move the mouse to place the cursor near the node or the center of the link and press the left mouse button. The program selects the nearest node or link center and highlights it to confirm that the ensuing operation affects the proper facility. If the cursor was actually closer to the wrong facility and, therefore, highlights the wrong thing, simply select again.
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• WINDOW in on any portion of your network. Control the window with the mouse by setting desired corners, or by zooming, or by sliding or panning. Back out to the previous window. A new window can be selected and redrawn in a matter of very few seconds. Drawing all links and/or nodes with widths proportional to some data values takes only slightly longer. The draw and redraw capabilities are very fast. You may also transfer (print) from the screen any view of the network to your dot matrix or laser printer or to a PCX file. Alternatively plots and .DXF files (as used in AutoCad or other programs) can be created as described in a following section.
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• EDIT or ENTER data for any intersection or street by pointing to it, then "click" on the data you wish to change and type in the correct numbers. Another powerful entry and editing tool is the BUFFER. It is a general storage location for data values. Data may be entered into the buffer by keying in or by pointing to a street or intersection that is already described by the desired set of data values. Any values contained in the buffer can then be assigned to any other street or intersection simply by clicking the mouse button on that street or intersection and then by confirming it with another click. Through use of the buffer, data are efficiently entered along a route. The data are keyed in for the first route segment, then each additional segment of that route can have the data duplicated in it through two mouse clicks.
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• DISPLAY the network and its attribute data values by color, proportional widths, and/or text. The specific streets and intersections affected by these display options may be limited by Class, Area, and/or Type and by a range of data values. For example, volumes may be displayed in proportional widths but limited to only major arterials and only those with volumes greater than 750 vehicles per hour, or intersections with V/C values greater than .85 may all be displayed in red, or the text values for all streets with a speed of zero (not yet or improperly entered) may be shown on those streets. The ability to pinpoint the data and the type of display, eliminating unwanted or cluttering data, allows the user to present material which appropriately emphasizes the problems or solutions in question. VERIFY data entry also by using the display capabilities. Draw speeds in proportional widths. Do the changes make sense? Draw numbers of lanes or capacities. Illogical data are relatively easy to find and are the ones most likely to cause problems with the general logic of the network.
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• LAYERS, files of useful line data, may be created and shown as background data for a network. TMODEL has the built-in ability to read Census Bureau TIGER files and create layer files which are subsets of the TIGER data. You may, for instance, display a roadways file and then digitize your network right on screen over it, leaving out the many streets irrelevant to traffic modeling. Or, you may display census tract, block group and block data in order to help develop your Traffic Analysis Zone (TAZ) structure. You may also import .DXF or MapInfo .MIF files to use as custom layers. Three (3) graphic layers may be displayed in addition to the network at any one time.
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• PEN PLOTS (LaserJet or DesignJet Plotters) are set up by the network graphic editor and then control is passed to the plotter. Plots are very useful in developing a model. First develop a "stick drawing" of the network. This requires intersection coordinates through digitizing or simply entering nodes over a layer. Then links are defined by playing "connect the dots" with the mouse. At this point, several pen plots can be drawn. These blank network maps can be given to whomever is responsible for the network descriptive data and volume count validation data, along with instructions to write the appropriate information on each map. For instance, one might enter free flow speeds on one map, enter all traffic controls on another, enter traffic count data on another, enter numbers of lanes on yet another. These can then be used as the base maps from which to enter the data into the program. After the data are entered, create a plot of the data text and have the collector or supplier of those data verify that all are correct. If not, they can make corrections on the maps. This furnishes a "paper trail" and a method of signing off completed steps. The ability to quickly make notebook size plots on a LaserJet printer makes the documentation process more efficient.
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• REPORTS are best made through maps. Since traffic simulation results are usually more apparent in graphic presentations, many will require hard copy output such as pen plots. Others can be transmitted in person using screen graphics. Consider innovative and more understandable ways of getting a point across. Volume to Capacity ratios, which are not intuitively apparent to some, can be presented in a very graphic method. Display the capacities in green proportional with bands using a selected scale range. Then overlay the volumes in the same selected scale range in red proportional widths. The amount of red to green is the V/C ratio and the amount of green visible is the reserve capacity. The ability to save screen views as .PCX files makes presentation of the results easy and colorful. TMODEL includes a module which helps you produce a "slide" show for presentations. Standard written reports are also available to present all of the data inputs and outputs of the model.
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• LINE EDITORS are available for spreadsheet-style data entry. If screen graphics are so great, why use data line editors? In some cases the data are organized in such a fashion that an experienced number pad operator can enter them more rapidly that way. Or data may be loaded directly from some other source. The best use is the line editor's capability to assign data values to more than one link at a time. For instance, in the link line editor, all capacities may be assigned a value on a per-lane basis which may then be limited by Class, Area and/or Type. As an example, all minor arterials (class=4) in the CBD (area=1) with parking (type=6) could be assigned a capacity of 975 VPH. The editor would then look up the number of lanes for each facility that satisfied those class, area and type requirements, multiply the number of lanes by 975 and enter the result in the Capacity columns for those streets. Macro changes or edits can be made in the same fashion, another aid to model development and calibration.

LAND USE - TRIP GENERATION

This is the process of taking known land-use data such as dwelling units and employment, applying peak hour, directional and trip type factors to compute productions and attractions (or origins and destinations) by trip type. TMODEL supports two methods of accomplishing these tasks. The first incorporates the methodology of NCHRP 187 and automatically balances productions and attractions for the entire model area. The second method allows the user to define an unlimited number of land uses and trip generation rates.

The ability to compare different origin and destination files is included. Further, land-use, origin-destination or trip table files can be displayed graphically.

DISTRIBUTION AND ASSIGNMENT

TMODEL runs in two different ways. For distribution and assignment, the preferred way, is an INTEGRATED distribution and assignment. This differs from most if not all other microcomputer models. Rather than distribute trips (create a trip table) all at once, based on a one-time look at all travel times through the network, TMODEL distributes incrementally as well as assigns incrementally. This means that as a destination becomes less accessible due to traffic congestion in its area, it becomes less desirable as a destination and alternative destinations are more likely to be chosen. While in most models congestion affects the assignment, we believe it should also affect trip distribution.

If you wish, the model can be run in more typical fashion, doing the distribution phase first and then an incremental assignment. gravity model is the basis for the distribution of trips. However, the program provides a unique formulation of the gravity model. It can be used in the more recognized standard fashion

All of the features of select zone, select link, multiple select link, subarea select link, and select trip purpose are available with either option.

GRAVITY MODEL

The gravity model is the basis for the distribution of trips. However, the program provides a unique formulation of the gravity model. It can be used in the more recognized standard fashion:

in which:

In this formulation, Distance raised to the exponent b is the "friction of distance" or the measure of accessibility. This term accounts for the reluctance to take longer trips but fails to account for the competition of other modes for short trips, especially the walking trip. In regional models this usually does not matter because there typically are no zones within walking distance of one another. However, in urban models, where one tall building could be a discrete land use zone, many auto trips could be distributed to a building across the street. This is logical according to the existing formulation of the gravity model but not logical in a traffic model. Therefore, the friction of distance term has been expanded to include another factor, D raised to the exponent alpha, and a structural constant, k, to differentiate their basic costs.

The new term for friction of distance is:

in which b, Beta, is typically positive and between 1 and 3, and a, Alpha, is typically negative, between -0.5 and -4 and the constant, k, is between 50 and 1000. The values used have been derived by matching distribution and assignment results with known trip length frequency distribution curves and have successfully reduced the numbers of runs required for calibration when those data exist.

CALIBRATION AIDS

The task of calibration is simply the process of adjusting, with justification, the set of rules and data in the mathematical model to produce traffic volumes that sufficiently approximate known volumes for some specific instant of time. It sounds much easier than it is.

The first difficulties lie in gathering data for that specific instant (peak hour or period) of time. Choices must be made as to which hour of the day, day of the week, season of the year, and year will be used as the base data.

Using TMODEL, a user may store counts directly into a link file, perform the comparison with the modeled volumes, and plot allowable link calibration errors according to NCHRP 255. You can then reconcile all counts to a specific day/date according to user-entered factors. Given enough count data, you may even use the counts to "back into" a possible trip table. This table can then be assigned to check for count consistency and counts which are at least mathematically possible (i.e., volumes entering intersections equal volumes leaving intersection).

With the help of these TMODEL features, a target traffic volume scenario is established. The next task is to calibrate the model until it reasonably approximates these volumes using the following calibration features:

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• EXTERNALS CALIBRATION is the process of getting the model to interact properly with the rest of the world. For each link that connects directly to the outside world, i.e., to an external zone, directional count data must be available. Then, that traffic must be separated into its X-X (eXternal to eXternal) component and its I-X (Internal to eXternal) and X-I (eXternal-Internal) components. Once these numbers are ascertained, the externals calibration process iteratively adjusts the external zone productions and attractions to produce the appropriate counts on the links connecting the external zones to the internal network. This task, once very time and energy consuming, is automated.
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• SCREENLINE ANALYSIS can then be performed. The user may define screenlines or cordon lines by the links which cross them. The program will then use the link file that contains count data to establish a screenline analysis file. After each calibration run, this file can then be automatically compared with the assignment results. This generates a report of the model's assignment accuracy across screenlines by direction. If screenline crossings are high or low, the planner or engineer can then begin to question his assumptions or data for a) land use, b) trip generation rates, or c) gravity model exponents. Solution is typically sought first in the area of most questionable data. Screenline analysis data can also be exported to be examined in the Network Graphic Editor.
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• DIFFERENCING is the notion of subtracting the results of one run or set of data from another to ascertain change. For example, base count files for both links and turns can be subtracted from assignment run files to generate reports of the differences between the model and the data for which it is being calibrated.
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• SCATTERGRAMS are available to examine the correlation between directional traffic counts and model assignment volumes. Key statistics as well as recommended maximum allowable errors are reported. Graphs can be created for subsets of the data for more detailed analysis. Analysis data can also be exported to be examined in the Network Graphic Editor.
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• SELECT ZONE ANALYSIS is available to study the volume, percentages, and patterns of trips to and from any two groups of zones (districts) in a simulation run. The user also has the option of analyzing intra-district or inter-district trips. This feature is especially useful for studying the impacts of new developments. The development traffic can be "tracked" across the entire network.
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• SELECT LINK ANALYSIS is used to evaluate the trips using an individual link. A trip table recording the origins and destinations of these trips is saved and the paths used by the select link trips can be displayed using the screen graphics editor. The trip table can be evaluated with travel characteristics graphics.
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• SELECT TRIP PURPOSE ANALYSIS is used to evaluate specific trip purposes or types. A new bus route may be considered in a corridor with significant number of HBW trips.
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• LAND USE AND TRAVEL CHARACTER-ISTICS GRAPHICS are used to analyze the model. This powerful graphic analysis tool can be used to display the land use quantities, numbers of origins and destinations by trip purpose or totals, and terminal times or intrazonal times by zone. A more powerful use is to analyze the trip distribution showing the number of trips by origin or destination to or from a particular origin zone. Travel time isochrones and modal share impedances can be displayed to or from any zone.

POST-DISTRIBUTION AND ASSIGNMENT ANALYSES

Once a calibrated model is available and alternative scenario testing is done, the final step is making the results of that "what if" test useful. In addition to the various methods of mapping using color, width and text on links and nodes, TMODEL provides the capability of:

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• generating statistics and summaries for any data or combinations of data
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• limiting the presentation or use of data by Class, Area and/or Type or to certain ranges of values
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• building formulas to use any of the link file data in combination with constants chosen by the user to develop new measures. This can be used for looking at things as straightforward as V/C ratios to more complex issues, such as traffic density, Level of Service (LOS), pollution indices and cost/benefit analyses.

TURN MOVEMENT ANALYSIS

The ability to capture turn movement counts, calibrate toward those counts, and compare them with base data counts and with future scenario counts is built into TMODEL. The turn counts can be inspected with a graphic presentation. Forecast turn volumes can be adjusted for localized error using Fratar and differencing techniques.

Turn counts can be saved for select zone, link, or trip purpose designations. Further, the turn count data can be loaded from the file directly into the NCAP program for capacity analysis. This capability can also be used to help derive or check appropriate node delay coefficients and turn penalties by intersection or by movement.

RENUMBERING UTILITIES

This utility allows the user to build a correspondence file between a set of existing node numbers and a new set and then renumber any file containing node numbers to the new arrangement automatically. Nodes can be selected for renumbering based upon coordinates so that they are more easily located. All files can be systematically renumbered to match any new network layout. This allows freedom to alter networks and zone structures in a relatively painless fashion.

VINE (TREE) BUILDING

A model that supports turn penalties must use a "vine" rather than the traditional "tree" of best paths from any particular origin zone. The difference is that a vine can cross back over itself whereas a tree does not allow passing through any particular node more than once. A vine allows using a node more than once but, does not allow using a particular link more than once.

TRIP TABLE MANIPULATION

The powerful trip table manipulation area of TMODEL provides the capabilities for squeezing (combining smaller zones into a larger zone) and expanding (splitting a large zone into smaller zones) trip tables. This allows the user to use existing trip tables from outside sources for some purposes or to analyze the model using Districts.

Further, there are several other manipulations available: checking sums by row, column and block; factoring matrix cells with restrictions on intrazonal trips; normalizing rows or columns; transposing; masking; merging; adding; and using Fratar techniques. Other features include the ability to convert directly from productions and attractions to origins and destinations in one step, as well as and convert a trip table into "links" to permit display of Desire Lines using the Graphic Editor.

MODE SPLIT METHODS

Both pre- and post-distribution mode split methods are available in TMODEL. Pre-distribution mode split allows the user to define origins and destinations to and from a zone based upon parameters such as household income, automobile ownership, proximity to a transit line, ride sharing incentives and other measures. This method of mode split is very flexible, allowing you to define the parameters to be used and the degree of importance. This method also can be used to reflect differences in trip generation for individual zones based upon different parameters.

Post-distribution mode split allows up to nine different modes to be differentiated based upon differences in the travel times between the different modes. In this method, a person trip table is created and then the different modal networks are skimmed for travel times. The travel times are used to create a "mask" which is used to factor the person trip table into trip tables for each mode. The person trip table can be created for each trip type and "masked" using parameters specific to the trip type being considered. This method allows use of the UMODEL formulation or a Pivot-Point Logit technique.

HOV/SOV

HOV/SOV assignment is designed to allow inclusion of modes which have limited or no access to some of the links and nodes of the network. TMODEL accomplishes this on a single, all-inclusive network by using separate input trip tables for each mode with different link and node delay coefficients and turn penalties for each mode. To represent HOV lanes, two parallel links can connect a pair of nodes, each with its own attributes. The results are stored in a loaded link file in which the volumes columns contain the total assignment, the SZ1 columns contain the assignment from the first mode, and the SZ2 contain the volumes for the second mode. Travel time matrices can be saved for each mode.

New options allow the use of MPA and UQP and up to nine (9) modes to be distributed and assigned at the same time.

SUBAREA ANALYSIS

Regions within the model may be isolated for further study using the Subarea Analysis option. This feature will capture all movements that enter or leave the area on pre-defined links. This can be used to analyze traffic through a community area, access to transit stations, or to develop a through-trip table for a windowed model. Origins and destinations are kept for each link as it enters or leaves the defined area.

Subarea networks can be extracted and automatically renumbered for use as windowed models. This can be particularly useful for traffic impact analysis.

EMISSIONS

TMODEL can compute emissions or fuel consumption on an hour by hour basis for the analysis of air quality. Traffic count variation curves are used to define volume characteristics throughout the day. Hourly traffic volumes and resulting operating speeds, including link and node delays, are computed using the hourly volumes. Emissions are then computed based upon both speed and VMT. Emissions can be summarized for any period and be exported to a link file for geographic location and plotting. Even when not required to evaluate emissions with improvement alternatives it is useful for analysis because it includes the combined impacts of traffic volume and operating speed in one graphic view.

LEVEL OF SERVICE

Level of Service (LOS) analysis, using tables from NCHRP Special Report 209 (1994 Highway Capacity Manual), can be easily performed. This analysis uses average operating speed, link density, traffic volumes, or V/C ratios to compare with the LOS tables. The display attribute files are automatically created and results can be plotted in the Network Graphic Editor.

CUSTOMER SUPPORT

Customer support includes the program documentation, the TMODEL workshops, the periodic user-group newsletter, email and Internet support and the toll free voice and fax support lines. In a constantly evolving and complex technology, such as transportation modeling, we believe that customer support is just as importance as technical excellence. We provide help with using the specific software and through our consulting practice, with the more basic issue of solving traffic analysis problems.

MORE INFORMATION

Once again, this is not an exhaustive listing of the capabilities of TMODEL. Our update program is vigorous and comprehensive. Capabilities are always improving, and we are always seeking the advice and suggestions of our customers. If you have further questions or suggestions, please contact us. The TMODEL manual (TMANUAL.TXT) and update changes (TMREADME.DOC) are on the TModel Corporation website available for download.

In addition to the full version, a sample version of TMODEL is available for people who would like to have some hands-on interactions with the program before making a final decision. An educational version is available for college and university use.

If you have any further questions, please feel free to give us a call at 1-800-T2MODEL, FAX us at 1- 800-T2MODLR, or Email us at tmodel@tmodel.com.

24505 Dockton Rd. SW
P.O. Box 1850
Vashon, WA 98070

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