Both .vrt and .clt files seems to be used by Autodesk software, so if any program is capable of somehow transforming these two files, it would be it. That's is, if this vrt to clt conversion is actually possible and useful, which we could not actually verify.
Convert Autodesk profile definition to Autodesk culvert data file.
We found one software available in the database for this conversion.
Multiplatform software - convert vrt to clt on any platform
CAD design software for engineering technicians, drafters, and surveyors
Convert from vrt file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.