|Location Map ( geo)|
|Distance:||4.7 miles (7.6 km)|
|Route outline (key)|
The C401 is in two distinct parts. The longer section forms a loop to the east of the A970 on the west side of Sullom Voe. It starts near Isleburgh and winds northwards, never far from the coast, to the small village of Sullom; this is the C401-010. At Sullom, it turns west and crosses back to the A970 near Johnnie Mann's Loch; this is the C401-030.
The other section of the C401 is the C401-100, which lies several miles to the north. It starts on the A970 at the head of Ura Firth and runs north to the staggered crossroads at Assater. Here it meets the C402-020, and there is no apparent reason why the two parts of this route have different numbers.