create_base_hwy()

This file will create the MHN output directorymfhrn_programs/output/1_travel if it is not already there, and if it is already there it will delete it and recreate it again. This ensures that you have a clean output directory which is not affected by previous runs of the program.

Once the MHN output directory is created, input/MHN.gdb will be copied into the MHN output directory with the name MHN_{base_year}.gdb. This is now the current geodatabase, so current_gdb is updated to point to here, and this geodatabase is appended to built_gdbs.

MHN_{base_year}.gdb is then prepared for edits. The relationship classes are deleted, and extra columns are added to the highway data which will facilitate the updates. Finally, get_hwy_dfs() is called to read the data from the current geodatabase into the pandas dataframes.