The bypass was completed in 1983,[2] re-routing the A143 around the northern edge of the town on the former Waveney Valley railway line which had closed to traffic in 1966.

[5][6] This splits the road in places before it is reunited at the southern edge of the town centre having passed the grade I listed St Mary's Church.

The road then passes Bungay Pool and Gym on the southern edge of the town before entering a rural section.

[7] In Spexhall parish it crosses the Lowestoft to Ipswich railway before arriving at the northern edge of Halesworth.

South of the town centre the westward section of the B1123 towards Metfield and Harleston joins the road, before the junction with the B1117 towards Laxfield and Stradbroke is reached.

It has generally been rated as medium or low–medium risk in European Road Assessment Programme (EuroRAP) surveys.