The "Ballard Why" is the interface from Hazelton Yard to the layout modules. The wye includes signals for each track going into the yard. Whenever needed, conflicting routes on other tracks are interlocked, power shut off to the conflicting tracks, while trains cross the wye entering the yard.
The mountain line on the upper track has two loops which assault the grade, about 3%, providing yard access for running on the "Hill."
