Hey Jerry...to answer your question...
Yes, Gargraves track lines up perfectly with Atlas track. No need for a transition piece. Atlas makes rail joiners that mate Atlas to Gargraves but I find them to be too tedious to use and often bend or break them.
What I do is just cut a slit in the bottom of the Gargraves rail with my Dremel and the regular Atlas track joiner slips right on. In the rare event the joint is not tight, I apply a little solder to the joiner.
Regardless, for me...it is Gargraves and ROSS. I use both of the ROSS switches and curves. I also like their preformed foam roadbed.
I only use Atlas track at my bridges and transfer table.
Donald
