|Length:||8.6 miles (13.8 km)|
|Meets:||A970, A971, A971|
|Route outline (key)|
The C309 comprises three very different pieces of road. The longest is the road which runs west from the A970 at Girlsta, before turning south and following the west shore of the Loch of Strom to meet the A971 at Haggersta. This is the C309-040, and then the C309-020.
A short distance south along the A971 from Haggersta, the C309-050 starts at Whiteness village and runs south along the narrow peninsula between Stromness Voe and Whiteness Voe to the end at South Whiteness.
The final section of the route is found a couple of miles north of Haggersta on the A971, where the C309-010 runs south along the west shore of Weisdale Voe to Cott, with the main road climbing up the hillside above.