In a development worth £107 million, a 4.8 km road will be provided in Neath Port Talbot, connecting the town to junction 38 of the motorway.
The project is funded by the Welsh Assembly Government and the European Union and is expected to ease traffic and attract investment.
Economy and transport minister Ieuan Wyn Jones stated the money would be made available "despite challenging economic times".
Elsewhere, leader of the local authority Ali Thomas described the move as "excellent news" for the region.
As much as 210 hectares of land will be freed up for development by small and medium-sized businesses when the work is complete.
This comes after the Homes and Communities Council Agency donated £3 million to an environmentally-friendly housing development in Hartlepool's Belle Vue area.
Written by Ryan Gilbert