It connects central-Senegal with Basse Casamance by a route which crosses The Gambia.

The road runs in a southerly direction from Diourbel to Kaolack where it crosses the Saloum River before heading to Bounkiling in Casamance via The Gambia and swinging south-westward to follow the northern bank of the Casamance River to Bignona.

Turning southwards the road crosses the Casamance River to end in Ziguinchor.

[1] The road traverses central Gambia as the Trans-Gambia Highway linking Farafenni in the north to Soma in the south, crossing the Gambia River on the Senegambia Bridge.

An alternative route is the N5 via Bignona and Banjul, crossing the Gambia river by ferry at Banjul and rejoining the N4 just south of Kaolack.