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Last Updated: Wednesday, April 6, 2016 11:30 AM

CALINE4 Software

Caltrans Software License (Please review before downloading files!)

Download CALINE4

Download CL4 v.2.1 zip archive - use Winzip or other extraction tool to view (250KB archive file)

Bugs have been discovered in the CALINE4 100-link version. Do not use the 100-link executable previously available here.


CALINE4, California Line Source Dispersion Model, Version 4 (CALINE4), is the standard modeling program used by Caltrans to assess carbon monoxide impacts near transportation facilities, as described in Appendix B of the CO2 Protocol. It is based on the Gaussian diffusion equation used in CALINE3, which is the basis for U.S. EPA's line-source dispersion models CAL3QHC and CAL3QHCR, but has a few enhancements that improve model performance compared to CALINE3.

CALINE4 was developed in the late 1980's at Caltrans' Transportation Laboratory. It is used in California at this time only for CO2 analysis, but can also handle dispersion modeling of Particulate Matter (PM) and nitrogen dioxide (NO2). A number of special modes are also available in the model that are not used when performing CO2 analysis according to CO2 Protocol procedures. Full documentation of the model is in the 1989 research report. If analysis using the special modes, or for some types of PM or NO2 analysis, is necessary, CALINE4 can be run as a command-line program rather than through the CL4 user interface, after preparing an input file as described in the Caline4 Manual. The latest CL4 user interface (version 2.1, below) supports very basic modeling of PM and NO2. Commercial user interfaces for line-source modeling are also available that incorporate CALINE4.

CALINE4 (CL4) IS ONLY ACCEPTED BY U.S. EPA FOR CO ANALYSIS IN CALIFORNIA; for other pollutants or in other parts of the U.S., use CAL3QHCR Exit Caltrans Website or AERMOD Exit Caltrans website if EPA approval is needed (such as for conformity hot spot analysis). See EPA's Project-Level Conformity Analysis web site Exit Caltrans website and Support Center for Regulatory Atmospheric Modeling (SCRAM) Exit Caltrans website for details.

Caltrans does not at this time provide public training regarding use of CALINE4. Training vendors may have dispersion model training that includes CALINE4 or other line-source models, but Caltrans has no direct knowledge of and cannot provide recommendations about such training.

Like other dispersion models, CALINE4 requires input of traffic characteristics (volumes, speeds, etc.) and emission factors. In California, the EMFAC emission model is used. Normally, the latest version available from the Air Resources Board is used, but for transportation conformity analysis purposes the EMFAC version that has been officially "made available" by the U.S. EPA is used. For more information about EMFAC see the EMFAC page at this site.

CALINE4 Technical Notes

The CALINE4 100-link version previously available here has been withdrawn because bugs related to formatting and a possible endless-loop condition with more than 20 links were discovered. Please do not use the 100-link version. The original 20-link version appears to work properly and is included in the zip file linked above.

The current CL4 user interface limits analyses to 20 links and receptors because of limitations in the underlying CALINE4 executable module. If analysis requires more links and receptors consider breaking it up and using multiple CALINE4 runs.

CALINE4 can be used for analyses that are not covered by the CL4 user interface. See the CALINE4 Manual for information about building the input file and other model options. Command-line "redirection" is used to specify the input and output files when running the CALINE4 module by itself. The command line would look like:

>[program file path]\caline4 <input.txt >output.prn

The CALINE4 input file is plain text in a specific format; see the Manual for more information. The output file is plain text with mainframe-style "carriage control" characters in the first column.

As of CL4 v.2.1, CL4 no longer requires any special installation steps. Simply extract the downloaded zip file to a suitable directory. The directory should be accessible with full (read/write) privileges by the user, since input and output files for the model must be written there.

CL4 v.2.1 is based on .NET 2. If .NET 2-3.5 is not available on the user's computer, it will need to be downloaded from Microsoft Exit Caltrans website and installed before using CL4. Use caution with .NET 4 and higher; some features of .NET 2 are no longer supported at that level, and CL4 has not been tested with it. Multiple versions of the .NET runtime can coexist on the same computer. The CALINE4.EXE module is a stand-alone executable file.


Some users attempting to run CALINE4 may get an "altitude out of range" or "type mismatch" error. This error commonly occurs for the following reasons:

  1. The Windows™ decimal point default is set to a comma (",") rather than a period ("."). The CALINE4.EXE module expects to see all decimal points as periods. This is a common reason for the error when the model is used outside the USA. The Windows™ decimal point must be set to a period ("."), the USA default setting, in order to run CL4 or CALINE4.
  2. (SCAL * UALT) is less than 0 or greater than 10000. The error occurs if an altitude of 10001 meters or greater, or less than 0, is used. Users should not experience this error if using the CL4 interface, which is designed to prevent entering invalid altitude values. Most likely, this problem indicates a corrupted control file. Users creating their own control files (when using CALINE4 for pollutants other than CO, for instance) should be especially aware of this issue.

Here is a simple example control file (as saved by CL4):

55.0 28.0 0.0 0.0 1 1 1.0 1 1 60.0
30.0 0.0 1.8
1 99.0 -5.0 -99.0 5.0 0.0 30.0 0.0 0.0 0
11101Hour 1
270.0 1.0 6 1000.0 15.0 3.0 10.0

(bold emphasis added)

The sample file uses an altitude of 60 meters. This is stored on line 3 above as a SCAL of 1.0 and a UALT of 60.0. The user should look for this on line 3 of the control file (and fix if necessary). Control files are usually found in the program directory for CALINE4, with a file extension of ".DAT".

NO2 Note:

Caltrans does not curently use CALINE4 for NO2 analysis, but the model can accommodate it. Consult the 1989 report for more information. If modern NO2 emission factors are used, the results may appear to be zero because of underflow in the output formatting. Users may wish to scale up their NO2 input data then scale the results back down to avoid this problem.

General Notes

All products except "PDF" documents are distributed as compressed archive files that can be opened with an "unzip" utility (such as Exit Caltrans website Winzip, 7-Zip, or the built-in ZIP function of recent Windows versions).

The CALINE4 model is copyright © of the State of California. Source code is not distributed.

Portions of the executable software may be copyright © Microsoft and others.

Windows and variatons on the Windows term related to the operating system, .NET, and Microsoft are trademarks™ of Microsoft Corp. Adobe, PDF, Acrobat Reader, and Adobe Reader are trademarks™ of Adobe Corp. Winzip and 7-Zip are trademarks™ of or copyright © by Winzip Computing and Igor Pavlov respectively.

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