This is based on the masonry arch bridge from the west side of Girard Avenue to the east
side of East River Drive in Philadelphia, PA.
NOTE: If you wish to use different track the buiult-in track can be removed by deleting the attached-track
section in the config file and also deleting Part_2 thru Part_6 sections in the config files mesh-table.
The track attachment points will still be in the Part_1 imafe file so as long as you do not delete Part_2
thru Part_6 image files from the folder the built-in track can be put back by re-typing the necessary text.