The first step was to decide what would be on each layer. Much would be built as separate reliefs and then merged at the end.
I then made a vector around the outside. This would be a zero height relief to which everything would be merged.
Then I began modifying this relief by adding the letter borders starting with the lowest level.
Then it was the next border layer.
Then it was time to raise the letters.
Then it was time to build the curved beam and tracks. These reliefs were built separately. The beam and rail center were done at the same height.
The rail ties were next.
Then came the bottom flange of the rail.
The top rail was the last relief to be created.
Then it was a simple matter of merging (highest) everything to the background relief.