If you mean track with double guard rails then you need Shinohara #669-117.
They also make single guard rail track, I'm thinking for mountainous curves.
"Flex Track w/Double Guard Rail 39" (1m) Long
Walthers Part # 669-117, p. 279 Walthers 2010 HO Scale Reference
HO scale, $18.00, currently in stock at Walthers"
By the way I made my own by gluing code 83 rails to the inside of the code 100 rails.