Slow approvals of Public Private Partnerships usually puts off high quality investors.
The project is expected to gift Tanzania with its first high-speed railway.
World Kaihatsu Kogyo is finalising work on phase one of the Ngong Road dualling project.
Nairobi has discarded the Dar es Salaam model that has been found wanting.
AfDB has reportedly declined to disburse the first instalment of the loan.
Groupe ADP beat intense competition with several multinationals to clinch the deal.
The runway will nearly double the movement of aircraft from 25 to 45 per hour.
In February, Yapi Merkezi and Mota-Engil Africa were hired for the project.
The signing of the deal will enable the contractor to kick off works by January next year.
The re-introduction of toll stations is, however, likely to face huge legal encounters.