What does that sign mean ?

[Biased turkey]

Could someone please tell me what that yellow disk with the "R 450" mean ?
Tia for any explanation or information.

 

[COMBAT]

Switch number???

 

[TruckLover]

Got me, I always wondered what those mean but never had a good example to post ops: lol

 

[Squidbait]

I believe that's the track/turnout number in the car-control territory.

 

[Biased turkey]

Thanks to all of you for the information . That was an easy question wasn't it ?