This article is about the Class III road numbered C51 maintained by Falkirk Council. For other roads numbered C51, see C51.
The C51 number seems to apply to a collection of roads north of Polmont. Based on the road names listed as part of the C51, it starts at the Lathallan Interchange and heads north through the golf course on Avonbridge Road. It probably includes the short link to the A905, but the mainline swings west, onto the former B904, becoming Smiddy Brae at Old Polmont. From the T junction here, both Grange Road, heading north to the A905, and Bo'ness Road heading south, the old B904 route, to the A803 are included as part of the C51.