I can think ov several examples of this if I understand what you mean. Where the mainline is in a curve and the spur/siding diverges to the outside making the main track the curve?

We have such a case on the OPR at East Portland where the OPR interchange switch is in a left hand curve and diverges into the yard on a # 10 turnout. These are expensive turnouts to maintain due to the switch point always being in contact with the wheel flanges and the chance of derailment ib a facing point move. The switch points are almost always undercut (refered to as a "sampson point" in that they are tapered thicker at the top of the point and the stock rail is undercut to fit. Frogs in such turnouts also get more wear and they generally use longer guard rails adjacent to the frog. Such turnouts are avoided if AT ALL POSSIBLE!!!

Another type is where the diverging track goes to the inside of the curve which takes up a lot of room since both tracks are curving the same direction. These take up almost twice as much room as a conventional turnout particularly the additional room it taksa to get the "clear point" where the track centers are 14-feet apart. This depends of course on the number of the turnout.

The most efficient form of turnout space-wise is the equillateral or "Y" turnout where both tracks diverge on a curve; here you can put a #10 turnout in about the same space as a #7 standard one.

Shortline Sammie