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Traffic Noise Model: Frequently Asked Questions FAQs

Table of Contents

This following are frequently asked questions (FAQs) about the FHWA TNM information. The FAQs apply to all versions of TNM, unless specified. This information is current as of April 2004.

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General Information

  1. What are TNM's system requirements?
  2. Where can I obtain TNM?
  3. What is the most recent version of TNM?
  4. Can I run multiple versions of TNM on my computer?
  5. Where can I upgrade TNM from Version 1.0b to Version 1.1?
  6. Where can I upgrade TNM from Version 1.0b to the most recent version, TNM 2.5?
  7. How do I configure my monitor display to work with TNM?
  8. Should I turn my computer screen saver off while running TNM?
  9. What is a "move" data error during installation?
  10. Where can I obtain a copy of the TNM User's Guide 2.5 Addendum?
  11. Where can I obtain technical support?
  12. Do I have to use TNM?.
  13. Why does TNM Version 1.1 sometimes crash when I try to open an input dialog or an output table?
  14. Is it possible to copy and paste multiple rows?
  15. What is the difference between TNM "dialogs" and TNM "tables"?
  16. Why can't I get to some of the buttons on the right side of a dialog?
  17. I entered data into the header area, but why doesn't it show up in the Plan view?
  18. Is TNM version 2.5 compatible with previous versions?

Menu: File

Save

  1. Is there a character limit in naming my TNM run?
  2. How do I delete unwanted TNM runs?

Import DXF/Stamina

  1. Does TNM import DXF Point Objects?
  2. When I import Metric DXF files in TNM the background units are incorrect. How do I fix this?
  3. My DXF file is about a 6 MB file. Is that too big?
  4. What's the difference between importing my DXF file as Objects and as Background?
  5. What DXF objects can TNM import?
  6. How do I import large DXF files as Objects?
  7. I imported a DXF file. Why can't I see anything in the Plan View?
  8. Why can't I import my Stamina file?
  9. What happened to the alpha factors in my imported STAMINA files?
  10. How do I import shielding factors in my STAMINA files?
  11. How do I import shielding factors in my STAMINA files with TNM Version 2.1 and above?
  12. Why can't I open the example files?
  13. Can you import multiple DXF files "as background" in TNM Versions 2.0 and later?
  14. Can I simultaneously import more than one DXF file as objects?

Open

  1. What is a TNM "run"?
  2. Can I open runs created in older versions of TNM in the most recent version of TNM?
  3. Can I open runs created in the most recent version of TNM with older versions of TNM?
  4. What does an "unable to find master dictionary" error mean when I try to create a new run or open an existing run?
  5. Why doesn't my run open?
  6. Why should I breakdown my run into smaller runs?
  7. What kinds of files can be imported into TNM?
  8. How can I print my input?
  9. How do I use the Set Print Scale when printing in TNM?

Menu: Edit

  1. How does the edit graphic functions work?
  2. Why doesn't Undo work when I mistyped a data entry?
  3. Can I cut/copy/paste graphical objects?
  4. Why doesn't the delete key work?
  5. Why doesn't copy and paste work in my input dialogs in TNM Version 1.1?

Menu: View

  1. Why doesn't my Skew Section show all the objects that I'd selected?
  2. Why can't I see my object point names and numbers?
  3. Why does Full View show me my objects reduced in one corner of the Plan view?

Menu: Setup

General

  1. Why can't I register coordinates of zero?
  2. What are the setup defaults for TNM?
  3. What kind of digitizer should I use with TNM?
  4. Why doesn't my digitizer work with TNM?

Register Plan

  1. How do I enter Z coordinates while digitizing everything else?
  2. Is it recommended that I digitize Z coordinates?
  3. Why does TNM give me an accuracy warning when my coordinates are off by a small amount?
  4. Does TNM accept the default XY coordinates of zero when digitizing objects?

Menu: Input

Receivers

  1. TNM outputs "invalid" results listed in the Sound Levels results table when I model berms. What is causing this error message?
  2. How do I assign adjustment factors in TNM?
  3. Why are my computed sound level results sometimes lower than my inputted Existing Levels?
  4. How do you add background noise to TNM results?
  5. Why don't my sound levels decrease when I input Adjustment Factors?
  6. Should I use adjustment factors for building rows or tree zones?
  7. Does calculating new active receivers invalidate previous sound level results?
  8. How do I model a reference microphone above a barrier?
  9. How do I activate/deactivate receivers?
  10. Is there any information regarding what to do to account for the loss of noise indoors?

Roadways

  1. How do I model roadway medians?
  2. How do I model roadway medians?
  3. Do I need to be careful to avoid my roadway widths from overlapping?
  4. Can I model multiple lanes using a single, equally wide lane?
  5. Do I need to be careful to avoid my roadway widths from overlapping?
  6. What is "average" pavement?
  7. How should roadway intersections be modeled?
  8. Can TNM model vehicle deceleration?
  9. How should I model TNM roadways when considering grade adjustments?
  10. How do I model roadway shoulders?
  11. How do I create a user-defined vehicle?
  12. When inputting traffic speeds, should I use the posted speed limits?
  13. How long should my roadways be?
  14. How do I input Ldn and Lden data in TNM?
  15. How do I input Ldn and Lden data in TNM Version 2.1 and above?
  16. How does TNM compute acceleration on roadways with traffic-control devices?
  17. How do I calculate roadway contributions?
  18. When should I use "on struct"?
  19. How do I model roadways with super elevated roadways (cross-slopes)?
  20. Should I model slow and fast lanes separately?
  21. Should I model HOV and truck lanes separately?
  22. When does TNM stop acceleration for traffic on a roadway?
  23. When digitizing roadways, how close should I match the curves in the Plan View?
  24. Are roadways allowed to intersect with other TNM objects?
  25. What is the maximum speed I can model heavy trucks in TNM?
  26. I am interested in modeling vehicles idling. Would modeling their speed limit at 1 mph accomplish this and be an accurate representation?
  27. How can the newer pavement types be credited in the TNM?
  28. If I have a 45 mph secondary road with a stop sign, it appears to me that taking flow control into account is not really necessary. Are people finding meaningful differences by including flow control?
  29. We are provided ADT traffic volume for a given roadway. Page 63, Item 4 at the bottom of the page (TNM User's Guide) asks if you wish to apply traffic to the entire roadway. Does the software divide the ADT between northbound and southbound or does the user have to input half? e.g. if the combined traffic in both directions is 22,000, does the user enter 11,000 or 22,000?
  30. Why do my Stamina roadways only show 3 vehicle types?
  31. What is the point of taking noise field measurements - just to see if your data is close?
  32. How do I use my traffic data to "calibrate" my TNM run to existing conditions?
  33. When should I use average pavement?
  34. Can TNM calculate two traffic types simultaneously (i.e., LAeqh1h and Ldn)?
  35. What happens when I switch the direction of a TNM roadway?

Barriers

  1. Why does TNM give a flat top berm warning when I enter in a non-zero berm top width value?
  2. Should I model my berm as a wedge or with a flat top?
  3. What are the three ways of entering barriers that will affect the sound level results?
  4. How and when do I model Jersey barriers?
  5. How does TNM calculate insertion loss?
  6. How does ground type affect insertion loss?
  7. I'm perturbing the barrier up and down in the barrier view, but why aren't the results in the tables changing?
  8. I started to do a simple test run, which passes the input check and then immediately gives a "Segmentation Violation" dialog and stops the calculation. What does this mean?
  9. Does TNM allow barriers to be modeled underneath roadways on-struct (overpasses) or barriers on-struct?
  10. Why are my "No Barrier" and "With Barrier" sound level results the same?
  11. Does TNM account for sound being reflected off a barrier back over the roadway?
  12. Why doesn't TNM 1.1 recognize my berm design?
  13. TNM outputs "invalid" results listed in the Sound Levels results table when I model berms. What is causing this error message?
  14. How does TNM calculate Barrier Noise Reduction?
  15. How do I model concrete retaining walls?
  16. Should I model berms that are median barriers?
  17. In the Shielded List for structure barriers, why does it appear to have text and fields pertaining to adjustment factors?
  18. Which roadway segments can be shielded by structure barrier segments?
  19. What does an "HPP Count Mismatch" error message mean?
  20. What does a "segment skipped" error message mean?
  21. Why am I able to shift a fixed-height barrier to zero height?
  22. How long should my barriers be?
  23. How do I know which is the left or right side of a barrier?
  24. Does TNM calculate multiple perturbable barriers simultaneously?
  25. What steps should I take to place a wall on top of a berm?

Building Rows

  1. How precise should I be when considering the height of building rows?
  2. How about precision in determining building spacing?
  3. Does TNM account for the actual locations of gaps along a building row?
  4. Should I input a building row or a barrier?
  5. How much attenuation does TNM contribute for building rows?
  6. The Building Row dialog is cutoff on the right so I can't enter a building row percentage.

Terrain Lines

  1. Should I use terrain lines as often as possible?
  2. How does TNM handle terrain lines?
  3. Where should I put terrain lines?
  4. Where should I not put terrain lines?
  5. Should I model my berm as a wedge or with a flat top?
  6. Does TNM allow terrain lines to be modeled underneath roadways on-struct (overpasses) or barriers on-struct?

Ground Zones

  1. When should I model grass medians?
  2. How do I model roadway medians?
  3. How do I model roadway medians?
  4. Does a tree zone automatically define the ground type?
  5. When should I enter in a ground zone?
  6. What is the definition of field grass?
  7. How do I model hard and soft ground?

Tree Zones

  1. Does a tree zone automatically define the ground type?
  2. How does TNM compute tree zone attenuation?
  3. When should I model tree zones?

Menu: Calculate

  1. TNM outputs "invalid" results listed in the Sound Levels results table when I model berms. What is causing this error message?
  2. Does TNM allow barriers to be modeled underneath roadways on-struct (overpasses) or barriers on-struct?
  3. How does TNM calculate insertion loss?
  4. How does ground type affect insertion loss?
  5. How do you add background noise to TNM results?
  6. I started to do a simple test run, which passes the input check and then immediately gives a "Segmentation Violation" dialog and stops the calculation. What does this mean?
  7. Do I lose my results if the program crashes?
  8. Why are my "No Barrier" and "With Barrier" sound level results the same?
  9. How does TNM handle terrain lines?
  10. I ran the official TNM test case in Version 1.0b/1.1/2.0/2.1/2.5. Why didn't I obtain the same results as the table listed in Figure 75 (Page 152) of the TNM User's Guide?
  11. What does a "DB" error mean?
  12. What does a "Floating Point" error mean?
  13. What does an "HPP Count Mismatch" or an "SQRT Domain" error mean?
  14. What does a "Subdivision missed a segment" error mean?
  15. What does an "Assertion failed - Lemis" error mean?

Menu: Barrier Analysis

  1. Why do my barrier analyses seem to disappear?
  2. Why don't the results tables reflect changes I make in the barrier analysis?
  3. Why can't I create a new Barrier Analysis?
  4. Why does Line-of-Sight show yellow markers?

Menu: Parallel Barriers

  1. Can I use the Parallel Barrier analysis module to calculate single wall reflections?
  2. Can TNM model more than 2 parallel barriers?
  3. How often should I analyze parallel barriers if the cross-section shape changes along the roadway?
  4. When should I analyze my parallel barriers?
  5. Can I model inclined barriers or barriers with an angled lip in TNM?
  6. How do I draw a customized cross-section in the Parallel Barriers module, instead of using the cross section TNM builds?
  7. What are some things I should consider when calculating Parallel Barriers Cross Sections?
  8. Where should I place additional roadways in an existing parallel barrier analysis?
  9. Do I need to make sure I cross through receivers when creating my parallel barrier section cut?
  10. Do changes to the Parallel Barriers module input data invalidate results?

Menu: Contours

  1. When I tried to calculate a contour of sound levels, NMPlot outputs an "invalid floating point error" and then halts contour calculations. What is causing this?
  2. In Version 1.1: I took care of the "Out of Memory" problem, but now when I run NMPlot, I receive a FATAL ERROR message about the file format created by Noisemap not being the one expected by NMPlot. I had already downloaded NMPLOTX.EXE Version 3.06, so I don't think that's the problem. Is this something fixed in Version 2.0?
  3. Are contours allowed to intersect other TNM objects?
  4. How do I workaround an "NMPlot Out of Memory" error?
  5. How do I workaround an NMPlot "run-time 200" error in TNM previous to Version 2.0?
  6. How do I workaround a NMPlot "run-time 216" error?
  7. How do I workaround a "Noisemap grid file could not be opened" error?
  8. How do I obtain contours to run in TNM Version 1.1?
  9. Why does TNM require a barrier in my run in order to run contours?
  10. How do I run contours without a barrier?
  11. When will the contour module be updated?
  12. Why do contours take so long to run?
  13. I developed a noise reduction contour and saved the contour set with an extension of ".nrc", but when I try to load the contour set, TNM asks for a file with extensions of ".slc", ".idc", or ".ilc". How do I open the previously saved contour set?
  14. Are there specific objects that need to be present when producing contours?
  15. What contour tolerance should I use in TNM?
  16. What is the minimum grid spacing that should be used when computing contours?
  17. What grid height should I use when computing contours?
  18. Is there a character limit when naming Grid Files and contour sets?
  19. Why do the calculated contour lines seem to intersect one another and give separate sound level results?
  20. Can I encompass my entire TNM run with a noise contour?
  21. I'm using Version 1.0b to calculate contours but NMPlot says that the contour settings were either too high or too low. What does that mean?
  22. After calculating contours, the contour lines are displayed but no text is displayed for any object in the view. What is causing this?

Menu: Tables

Print Tables

  1. Why can't I print any of my tables in TNM Version 1.1?
  2. What does "invalid" mean in my results tables?
  3. When I print the results tables, why don't I see results for the active barrier design?
  4. Why can't I open my Sound Level Results tables?
  5. What does "inactive" mean in my results tables?
  6. What does "no calc" mean in my results tables?
  7. Why doesn't my exported table data include the header information?
Updated: 07/15/2011
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