Appendix I: Frequently Asked Questions

The following list of frequently asked questions has been developed over the last ten years of experience with TSIS and CORSIM.  The questions and answers are grouped by the tool that they apply to

CORSIM

How do I use CORSIM to model a toll booth?

A toll booth can be modeled several different ways.  The most popular way is to split a single NETSIM link into several parallel links and using a fixed time signal on each of the parallel links to model the delay at the booth.  See the “CORSIM City” demonstration file provided with the TSIS software for an example of this method

How do I use CORSIM to model a weigh station?

Use a combination of Record Types 24 and 25 to force all trucks to exit the freeway while all other vehicles remain on the freeway.  At the end of the off-ramp, use one or more NETSIM links with some type of control device to represent the time the trucks spend being weighed.  Have another NETSIM link feed an on-ramp back onto the freeway.

How do I use CORSIM to model a bi-directional freeway HOV lane?

Model the lane on two parallel opposing links and use different time periods to represent the times when the lane is in use in each direction.  Close the lane in the direction not being used.  Insert a transitional time period in which the lane is closed in both directions to allow vehicles to get out of the lane before it starts accepting traffic in the opposite direction.

What's the difference between on-line and off-line incident detection?

On-line incident detection is applied as the simulation proceeds.  Off-line incident detection is performed after the simulation is finished.  Off-line allows the detection to be performed more than once using different detection algorithms.  On-line only allows one detection algorithm.

What causes 6710 errors?

Error message 6710 states that a vehicle is on a lane that does not exist.  A 6710 error is usually caused by a problem with the leader-follower chain.  When a vehicle has a leader it simply follows that leader without bothering to look for geometric objects such as lane drops or the end of auxiliary lanes.  CORSIM assumes that the leader will react to those objects and the follower will stay behind the leader.  When there is an error in determining which vehicle is the leader of another vehicle, a follower can blindly drive off the end of an existing lane, causing a 6710 error.  Occasionally, the leader-follower errors are caused by programming bugs.  They can also be caused by improper inputs, such as links that are too short.  They can also be caused by a geometry that forms a complete circle, such as a cloverleaf with full auxiliary lanes connecting the branches.  An off-ramp that leads to an on-ramp that leads back onto the freeway will also cause leader-follower errors.

A 6710 error can also be caused by having more lanes on the NETSIM side of an interface than there are on the FRESIM side, where traffic flows from NETSIM into FRESIM.  The number of lanes and the lane IDs must match on both sides of the interface node.

How can I increase the entry volume on my freeway network?

The default value for the minimum time between successive vehicles entering the network in a given lane (i.e., the “Minimum separation for generation of vehicles” parameter in CORSIM) is 1.6 seconds.  That limits the entry volume to 2,250 veh/h/lane.  If a higher volume is desired, then that default value should be decreased, which is entry 2 on Record Type 70 or on the “Miscellaneous” page of the “FRESIM Setup” dialog in TRAFED.  You might also need to reduce the car following sensitivity factors, which are on Record Type 68 or on the “Driver Behavior” page of the “FRESIM Setup” dialog in TRAFED, so that vehicles will remain closer to their leader after they enter the network.

Is there a good way to get queue length parameters from the CORSIM outputs?

Look for the "Average Queue by Lane" MOE in the output file.  The number reported is the average number of vehicles in queue.  If you select Intermediate Reports on Record Type 5 or on the “Reports” page of the “Network Properties” dialog in TRAFED, you will also get the queue length in feet.

Can I get time period specific output from CORSIM?

CORSIM will provide time period specific output in the output file (*.out) for the NETSIM subnetwork only.  However, the Output Processor was designed to report MOEs in three different modes: cumulative, interval specific, and time period specific.  All three modes work for NETSIM and FRESIM, as well as network wide.  Cumulative MOEs use data accumulated from the beginning of the simulation until the end of the current time period.  MOEs by interval use data accumulated over the current interval, and MOEs by time period use data accumulated over the current time period.  They can be selected individually or in any combination.

What causes numerous instances of warning message 720?

This is usually caused by the lane drop warning sign distance.  The warning sign for a lane drop should never be at a location with only one lane.  The warning sign location is really the point at which vehicles respond to the object associated with the warning sign.  If there is only one lane at the point, or only one lane usable by certain vehicles, the warning sign will be ignored.

Why do I observe incorrect traffic-actuated phase operations in conjunction with passage or pulse detectors?

The operational mode of the detector depends on what functionality it supports with regard to actuated control operations.  Presence mode should be used when the detector is being used solely to call the phase (e.g., a detector located at or near the stop bar).  Passage (pulse) mode detectors are typically used to support green extension and the volume/density operations of the actuated controller (e.g., variable initial and gap reduction functions).  When used for these purposes, the passage mode detector is typically located upstream of the stop bar and is primarily used to note the passage of a vehicle (green extension and gap reduction) or to count vehicles (variable initial timing).  If a passage mode detector is also being used to call the phase, then the yellow lock function for that phase should be set.  With yellow lock set, if any vehicle activates the detector during the yellow or red intervals of the phase, the controller will “remember” that the detector was activated and will call the phase.  Yellow lock also applies to presence mode detectors that are located upstream of the stop bar.

Why does the CORSIM output file show instances of the following warning messages: "Vehicles missed destinations - vehicle number...", and "Computed leader..."?

The message regarding missed destinations states that a vehicle was unable to get to its freeway off-ramp and missed its destination.  In this case, the vehicle will be rerouted to the next off-ramp downstream.  This will change the percentages of vehicles exiting at those off-ramps.  You should try to determine why so many vehicles are missing their destinations.  Consider off-ramp warning sign locations and any messages from CORSIM about vehicles not having acceptable candidate lanes to travel in.  The computed leader warning message indicates that the FRESIM lane change logic broke down, possibly because of incorrectly specified connections between freeways.

What is causing unusual or unrealistic traffic assignment results in NETSIM?

Unrealistic traffic assignment results will occur at actuated signals, because no methodology is present in CORSIM for estimating the average green times.  The traffic assignment logic also requires that all signalized or uncontrolled intersection approaches actually have vehicle volume on them.

What causes an actuated phase in NETSIM to terminate right after the minimum green time, even when volumes are heavy?

here have been several fixes to the actuated control logic included in TSIS/CORSIM version 6.0 which eliminated premature phase termination problems associated with the use of the volume/density functions.  If premature phase termination is still a problem when using TSIS/CORSIM 6.0:

• Check that the maximum green time (or maximum extension time) is properly set (i.e., not too low).
• For a coordinated controller, check that the split time is properly set (i.e., if too small, the phase may be forced off too soon).  Keep in mind the split time includes the minimum green, yellow interval, and red interval times.
• If gap reduction is enabled, check that the minimum and maximum gap settings are properly set (i.e., if too low, the phase may gap out even in heavy volume).

What causes warning message 725 (e.g., “While traveling on lane 1 on link (2, 3), vehicle 4 no longer has a candidate lane on which to travel.”)? 

Various downstream geometric objects, such as off-ramps, lane drops and incidents, force vehicles to avoid certain lanes.  When warning signs for those objects are not located correctly, the result can be that there are no lanes that should not be avoided by some, or all, vehicles.  A vehicle is in that situation will ignore the warning signs and stay in its current lane, which can cause vehicles to get stuck at lane drops or incidents, or take the wrong exit.  Vehicles begin to react to the geometric objects where the warning sign is located, so the combined effect of the warning signs must allow at least one lane that can be used by the vehicles that have crossed the warning sign.

How can I code "split phasing" for actuated controllers?

Suppose that split phasing is desired for the side-street approaches to an intersection where the side streets are oriented in an east-west direction.  For split phasing, all eastbound movements are served by a single phase, followed by a single phase for all westbound movements.  Typically, side-street phases are coded in dual-ring phases 3, 4, 7, and 8.  Phases 3 and 7 are designed to run concurrently because they are typically used for overlapping protected left turns.  Similarly, phases 4 and 8 are designed to run concurrently to support concurrent side-street phasing (both directions concurrently, with permitted left turns possible).  Because only one phase in each ring can be active, coding all eastbound movements in phase 3 and all westbound movements in phase 4 will implement split phasing.  Alternatively, phases 7 and 8 could be used.  Because CORSIM does not allow the specification of a barrier between phase 3 and 8 (or 4 and 7), they can also operate concurrently and cannot be used for split phasing.  Finally, a similar coding scheme can also be used to implement split phasing for the main-street approaches using phases 1 and 2 or phases 5 and 6.

How can I code an entry node volume greater than 9,999 vehicles per hour (veh/h)?

The limit for standard coding at a single entry node is 9,999 veh/h.  There are a couple of ways around that limitation.  One would be to create two or more entry nodes using 9,999 veh/h each, and then funnel that traffic onto the entry link.  Another way would be to specify the entry volume in terms of vehicle counts.  This allows 9,999 vehicles to be specified as a vehicle count, and allows counts as often as every minute.  Therefore the maximum that could be entered is 9,999 vehicles per minute, although there is an internal limitation of 1,500 vehicles per minute, so the absolute maximum for one entry node is 90,000 vehicles per hour.

Overall vehicular demand in the network is such that queues from downstream intersections are blocking upstream intersections.  This is having the effect that traffic cannot cross from the side streets and network-wide gridlock quickly occurs as the queues build back to subsequent intersections.  In reality, the city has implemented a "Do Not Enter" policy, where traffic is supposed to wait until vehicles clear the intersection before they proceed.  Is it possible to include the "Do Not Enter" condition in the model?

In TRAFED, you can select Network > NETSIM Setup > Spillback, to calibrate the probability of vehicles becoming or joining spillback.  For the scenario where no vehicles will block an intersection, enter values of “0” for all spillback parameters, meaning that there will be zero probability that a vehicle will join the back of a queue and block an intersection.

What causes fatal errors 6197 and 6198?

Fatal error messages 6197 and 6198 are often caused by a missing record type 25.  Off-ramps are defined by record type 25.  For the freeway mainline link, record type 25 must be coded to indicate which node receives off-ramp traffic.  Without record type 25, CORSIM cannot locate the off-ramp destination node.  When all of the necessary record type 25s are entered, this allows the origin-destination inputs on record type 74 to function properly.  These errors can also be caused by specifying a destination node that is not the upstream node of a mainline exit link or the upstream node of the first link of an off-ramp.

What causes the error message that says: “A fatal error was detected in the leader- follower chain.”?

There are multiple possibilities for the leader-follower error.  One possibility is that the network geometry involves a cloverleaf where a vehicle, in searching for a leader, follows a path that leads to itself as its leader.  There is a work around that involves breaking the path so that a vehicle will not find itself as its leader.  One way to accomplish this is to break the loop by adding a small NETSIM link in one of the loops of the cloverleaf.  Another solution is to break one of the full auxiliary lanes between connectors into an acceleration lane followed by a deceleration lane with at least on foot separation between the two.  The NETSIM link solution is probably the cleaner of the two because you can maintain the cloverleaf geometry better.  This problem is more likely to occur with networks that have very few vehicles but can occur in any network that has a continuous cloverleaf.

Another possible reason for this error is due to short link lengths, which can cause a corruption in the leader-follower chain.  When the link is short enough, and the free-flow speed is high enough, it becomes possible for a vehicle to completely jump over the short link during a one-second time step.  When this occurs, CORSIM's vehicle processing logic completely breaks down, and the result is usually leader-follower errors.  Beginning with TSIS/CORSIM version 5.0, CORSIM sends red-colored warning messages to the TSIS output window when it detects links that are short enough to cause modeling problems.

Correcting link free-flow speeds can also solve the leader-follower error.  FRESIM links connected to an interface node should have the same free-flow speed as NETSIM links on the opposite side.

A problem with the leader-follower chain can also be caused by a 2.0 second lane change interval and lane drop that has a warning sign only one foot upstream of the lane drop.  The warning sign location should always be far enough upstream so that vehicles can stop before reaching the lane drop if they cannot make a lane change. Vehicles reach the end of the lane and then other vehicles behind them pile up onto them.  Somewhere in that pile up, the leader-follower chain gets corrupted.

 How can I force more vehicles to use the outer lane (left most or right most) in NETSIM?

There are a few things you can try in order to better control vehicle paths or lane utilization in NETSIM:

• Channelization codes.  NETSIM can be calibrated to produce the correct lane utilization by using special channelization codes.  In order for this to work, it is necessary to select a channelization code for a turn movement (usually diagonal) that does not exist.  Just apply the diagonal channelization code to a particular lane, assign a percentage of turns to that diagonal movement, and then specify the correct left-turn, through, or right-turn receiving node for that diagonal movement.
• Turning movements that feed the downstream through node, sometimes used in conjunction with a dummy node.  This is a coding technique that encourages a certain percentage of vehicles to move into the outer most lanes.
• Conditional turning movements.  This input specification prevents vehicles from making consecutive unrealistic turn movements.
• Driver familiarity with path distribution.  By default 90 percent of drivers know their "goal lane", so some users change this to 100 percent so that drivers will make better decisions in advance.
• Interchanges.  Origin-destination data may be specified at interchanges and NETSIM determines the paths through the interchange and assigns vehicles to those paths accordingly.
• Driver cooperation.  The percentage of cooperative drivers can be increased.  The default is 50 percent.

Is it possible to specify freeway capacity per lane in FRESIM?

Although there is no explicit input parameter for freeway capacity, the inputs that can potentially affect freeway capacity in FRESIM include: Global or link-specific car following sensitivity factor, threshold speed and distance for anticipatory lane changing, minimum separation for vehicle generation, vehicle lengths, free-flow speed distribution, off-ramp warning sign distance, ramp and freeway number of lanes, acceleration/deceleration lane length, heavy vehicle percentages, off-ramp exit volume fractions, origin-destination volume fractions, simulated incidents, and queue spillback from arterial street signalized intersections.  Refer to chapter 5 for more specific information on calibrating the capacity of freeway bottlenecks.

What does "Network Did Not Reach Equilibrium" mean?

CORSIM networks contain no vehicles at the beginning of a run.  As the first seconds are simulated, vehicles are emitted onto the network from entry and source nodes.  The time required to fill the network with traffic is referred to as the initialization period. Because the initialization period does not accurately represent the conditions to be modeled, no statistics are gathered during this period.  A check is made at the end of every time interval for equilibrium.  Equilibrium is assumed when the number of vehicles in the network is within eight percent of the number of vehicles in the network during the previous time interval, and within 12 percent of the number of vehicles in the network during the second previous time interval.  In the CORSIM output file, this information is reported in the section called "Initialization Statistics".  Refer to appendix C for more information on the initialization period and reaching equilibrium.

Is there a way to input the volumes of weaving and non-weaving vehicles between an on-ramp and an off-ramp?

This can be done by specifying origin-destination information.  The user can specify an origin node and the percentage of vehicles that will exit at each destination node that can be reached from that origin.  Be careful in doing this, as this input overrides the coded off-ramp exiting vehicle fractions.

How can I model a major merge or diverge of freeways?

If a freeway branch is defined, the existing convention calls for one branch to be defined as the mainline, and for the other to be defined as the ramp.  Therefore, major merge or diverge sections must usually be modeled by defining "dummy" interface nodes and NETSIM links between the freeway sections.  If a dummy upstream mainline section is coded, NETSIM links may not be needed. 

How can I model a simple highway-to-highway connection?

Highways can be directly connected using FRESIM ramp links.  For a simple highway-to-highway connection, an off-ramp from the first highway may connect to an on-ramp onto the next highway.  However, there are limitations that sometimes require the use of NETSIM links.  When using FRESIM only, it is not possible to have a ramp that splits into two ramps, and it is not possible to have two ramps that merge into one.

What causes fatal error 6500 (e.g., “Link (32, 369) defined on RT 19 does not belong to any disjoint freeway segment.”)?

Fatal error 6500 is usually related to incorrectly specifying the link type (i.e., ramp versus mainline) or specifying invalid freeway segments.  Valid segments begin at an entry or entry interface node and end at an exit or exit interface node.  There must be a continuous sequence of mainline links between the beginning and the end of the segment.

How do I prevent vehicles that have just exited the freeway from immediately re-entering the freeway?  Specification of turning movement percentages does not prevent this behavior.

Use conditional turning movements.  In TRAFED, simply right-click on the affected intersection and in the "Intersection Properties" dialog box click on "Conditional Turning Movements."  Specify the conditional turn percentages for the approaches to the intersection such that vehicles that came from the freeway do not turn toward the freeway entrance.

Output Processor

I selected MOEs in the Output Processor and specified the “MS Excel” file format.  Where is the Excel file located?

The file containing the results from the Output Processor will be located in the same folder as the network input file.  If you have configured a tool that opens files with the .xls extension, the Excel file will be shown in the Project View.  The name of the file will depend on the Data Granularity that you selected.  If your input network is named “network.trf”, then the possible Excel file names will be “network_cumulative.xls,” “network_interval.xls,” and “network_time_period.xls.”

How is the Output Processor in TSIS/CORSIM version 6.0 different than the one introduced in version 5.1?

The Output Processor was introduced as a proof of concept in version 5.1.  It proved to be a very useful tool, but was limited in its capabilities.  It was redesigned for version 6.0 so that all MOEs computed by CORSIM could be accessed and, in addition, those MOEs could be accumulated by time step, time interval, or time period, or any combination of those.  Specific information is given in the CORSIM User’s Guide⁽¹⁾ in the section titled “Configuring and Running CORSIM.”

TRAFVU

Can I use a bitmap background?

Yes.  That capability was added in TSIS/CORSIM version 5.1.

How do I make a link curved?

TRAFVU uses the link curvature entry 4 on Record Type 196 to determine the curvature of all links.  This can be set in TRAFED on the link’s property dialog on the “Graphics” page.  The amount of curvature will depend on the length of the link and location of the nodes.

Why is my link curved at the ends when I set the link to be straight?

When two through links join at a node, TRAFVU tries to make them tangent at the node even if they are straight links.  You may get a small curve drawn so that they line up correctly at the node.  You can control the amount of curvature that is allowed for drawing purposes for individual links with a parameter on Record Type 196.

Why do some vehicles overlap in queue?

Most likely the length of the link as drawn by TRAFVU is shorter than the link length input for the link.  You can check this by right-clicking on the link and selecting the Geometric Data item while in TRAFVU.  Both the TRAFVU calculated length and the input length are displayed.  Remember that the link length is measured from upstream stop bar to downstream stop bar, not from node-to-node.  There can be quite a discrepancy between those two distances when the upstream and downstream intersections are not similar.  This is not only a drawing issue but can affect your link storage if not corrected.  CORSIM uses the link length from Record Type 11 when determining how many vehicles can be on the link, not the node-to-node distance. 

Why do some vehicles in queue have a large gap between them?

Most likely, the length of the link as drawn by TRAFVU is longer than the link length input for the link.  You can check this by right-clicking on the link and selecting the Geometric Data item while in TRAFVU.  Both the TRAFVU calculated length and the input length are displayed.  Remember that the link length is from upstream stop bar to downstream stop bar, not from node-to-node.  There can be quite a discrepancy between those two distances when the upstream and downstream intersections are not similar.  This is not only a drawing issue but can affect your link storage if not corrected.  CORSIM uses the link length from Record Type 11 when determining how many vehicles can be on the link, not the node-to-node distance.

Why do some vehicles overlap during lane changing?

CORSIM uses a grace period when making a lane change so that vehicles can make their way into the new lane.  CORSIM allows vehicles to overlap during this grace period.  TRAFVU places the vehicles in the lane and at the distance along the link where CORSIM dictates.

Why do some left turning vehicles “Crash” into opposing left turners in the middle of an intersection?

TRAFVU draws simple curved paths from the end of one link to start of the next link.  If the size of the intersection is not very big, these paths can overlap.  In real life, drivers would adjust their path to avoid this collision.

How can I see the node numbers in TRAFVU?

Hold the shift key down when you click on a node to display all the node numbers for the nodes in view.

Can I change the background color of TRAFVU?

Yes, this can be done through the Options > Window menu item, which displays the “Preferences” dialog for the selected window.  The “Background” page allows you to change the color of the background.  Changing the background color can be helpful when printing or comparing two test cases.

How can I save an image of the TRAFVU display?

You can hit the “Print Screen” button on your keyboard, which copies the image currently displayed on the screen to the Windows clipboard.  You can then paste the image in a graphics program like Microsoft Paint.  Holding the “Alt” key down while hitting the Print Screen button will copy only the window with focus.

Where is the link length measured?

TRAFVU uses the left curb length from upstream stop bar to downstream stop bar for its “calculated length”.

Why do I get a CORSIM warning if I use TRAFVU’s “calculated length” as the link length?

CORSIM uses simple geometry to take the difference between the upstream and downstream nodes to do a “reality” check on the link length.  CORSIM does not report the actual stop bar to stop bar distance that it should use for this check.  TRAFVU reports the correct distance in most cases.

The bitmap background image is not visible within TRAFVU.  Is there any size limitation for the bitmap background file?

Yes.  Bitmaps are stored on disk differently depending on the type of bitmap.  24-bit color bitmaps use 3 bytes per pixel, 256 color bitmaps use 1 byte per pixel, 16 color bitmaps use 2 pixels per byte, and black and white bitmaps use 8 pixels per byte.  So the size of the file can change dramatically based on the type of bitmap.  Depending on the image that is trying to be loaded and the purpose of the image, reducing a 24-bit color image to a 256 color image could buy a lot better resolution.  Orienting the image so the longer direction is vertical could allow a bigger bitmap than orienting it horizontally.

Why does there appear to be an abnormal spacing of vehicles on certain links, or, why do vehicles appear to be stacking on top of one another on certain links?

This usually indicates a mismatch between the link length input to CORSIM (which is the distance from the upstream stop bar to the downstream stop bar) and the link length calculated by TRAFVU (which uses node coordinates and the location of other links to determine where the stop bars are located).  This mismatch forces TRAFVU to stretch or compress the link, in order to be consistent with the node coordinates.  TRAFVU draws vehicles according to their length without compressing or stretching them, so sometimes it appears that the vehicles are farther apart, and sometimes it appears that they are overlapping each other.

The solution is to enter consistent link lengths and node coordinates.  TRAFVU locates the node at the point where the left curbs intersect.  The locations of the stop bars are then determined by considering the way the links connect and the number of lanes on the links.  Read section 3.3.2 in the TRAFVU User's Guide⁽¹⁹⁾ for more details.

The node-to-node distance is not necessarily equal to the link length.  The link length is the stop bar to stop bar distance.  The intersection width needs to be added to the node-to-node distance.  Select the link in TRAFVU and right click the mouse.  Select Geometric Data, and compare "TRAFVU calculated length" to "length".  Those numbers should be the same, or nearly the same.  If they are different, take the TRAFVU calculated length and use it as the link length.

TRAFED

Can I use a scaled bitmap as a background for my network?

Yes, an aerial photo, map, or drawing can be used as tool to layout a network.  By scaling the bitmap correctly, links and nodes can be drawn on top of the bitmap.  Using this method, you can quickly layout a large network.  The bitmap can be scaled and the position adjusted in TRAFED.  TRAFED is not a bitmap editor however.  If you need to rotate or edit the bitmap you will need to edit it with a different program.

How do I put in an entry or exit node?

You cannot explicitly put in an entry or exit node in TRAFED.  These 8000 nodes are created when you drag out a link to a location that does not currently have a node (“green space”).  The entry nodes are represented by a ‘+’ (plus) sign and exit nodes are represented by a ‘-‘ (minus) sign.  If you start dragging a link from an existing entry/exit node, it will be changed into an internal node that connects the two links.  You can drag out an entire network without ever placing nodes!

How do I put in an interface node?

You cannot explicitly create an interface node.  Interface nodes and interface links are created automatically by TRAFED when you drag a link from one type of network to another type of network.  For example, drag a one-way link from a surface node to a freeway node and you will get a surface interface link, an interface node, a freeway interface link, a required freeway dummy node, and another freeway ramp link between the two original nodes.

How do I create links of a different type?

The “Default Link Type” menu item on the “Network” menu controls the default link type that is dragged out by using the One-Way Link or the Two-Way Link tools.  However, when you drag out a link from an existing node or to an existing node, the link that is created will be of the type of node, no matter what the default link type is set to.  For example, dragging a link from a Freeway node will create a freeway link even if the default link type is set to surface street.

Why does TRAFED use a TNO file instead of a TRF file?

The TNO file is arranged so that all the similar data is stored together and written in XML format.  The data can be in a variety of different formats and is not restricted by the 80-column punch card format of the TRF file.  Because the XML format requires individual pieces of data to be tagged, the data can be added, subtracted, changed, or moved without causing problems between versions.  The TNO file also contains additional data that the simulation does not use, like the name of the bitmap background file.

Can TRAFED create a TRF file automatically?

Yes, the “TRF File Generation” tab on the “Preferences” dialog (located on the “Network” menu item) controls the automatic creation of a TRF file when you save the TNO file.  This a user preference so you can turn this behavior off during a network’s initial creation stages and then back on when only minor adjustments are being made.

What is the difference between the “Translator” tool and the “Export” menu?

The translator is a stand-alone program that will translate TNO format data into TRF format data and visa versa.  It has to load the data from the files first before it does the translation.  Exporting is done from within TRAFED and only exports out to TRF format.  Because it uses the data that is currently loaded in TRAFED, it is much faster than translating the data.  They both use the same underlying code so the result is the same.

Can I enlarge the drawing area while I am creating a network with TRAFED?

Yes, TRAFED can toggle between full screen mode and regular mode by hitting the “F2” key.  This allows TRAFED to be the full size of the screen for maximum editing area.  Pressing “F2” again will return TRAFED to it normal place inside of TShell.

Where should I place my nodes?

For the most part you should place your surface street nodes at the left curb for non-intersection nodes or at the extension of the left curb for nodes in the center of an intersection.  For freeway links, place the node at the left edge of the mainline link.

• For example, a four-way intersection with four approaches and four departures of the same number of lanes, the node will be in the center of the intersection.  For an intersection of two one-way streets, the node will be located at the crossing point of the left curbs (not in the center of the intersection).  If the user moves the node location, the intersection and connected links will also move to reflect the change.  One example of when the left curb rule is not true is when there is a link that merges with another link (e.g., on-ramp).  The link to the right will not have its left curb over the node.  The left curb will be placed where it needs to align properly.  These same rules apply in the FRESIM and NETSIM subnetworks.
• The node coordinate is only used in CORSIM to get the node-to-node distance as a preliminary check of a link's length.  CORSIM does not use it for any other purpose, as it is used purely for graphical display purposes in TRAFED and TRAFVU.

Why does the software sometimes say "Parse Error: not well-formed"?

There is a known problem concerning non-standard characters.  The XML parser that TRAFED uses can only process the standard character set, which includes all ASCII codes less than or equal to 127.  The extended character set, which includes all ASCII codes greater than 127, is not supported.  For example, when the problem is caused by an input file that contains the special character “û”, replacing it with a standard “u” eliminates the problem.