The accord had been inked on the margins of the 7th Regional Economic Cooperation Conference on Afghanistan (RECCA VII) in Ashgabat in mid-November.
Rail tracks and motorways are likely to connect the Torghundi town of Herat with Ashgabat and Caspian port of Turkmenbashi, Trend news agency reported.
It added the corridor will stretch to Baku before reaching Ankara through Tbilisi. It will include branches to Poti, Batumi, Ankara and Istanbul.
Designed to boost regional trade and economic integration, the project will cost about $2 billion.