The 182km high-speed line will extend the existing 180km route from Paris to Le Mans. The new line involves an investment of more than €3.3bn (£2.9bn).
In total, the agreement covers 214km of new line with 32 km of connections to the existing lines. There will be about 200 engineered structures, including 10 viaducts.
Studies and discussions will continue until July next year, when preliminary work will start on site. Completion of work is due in autumn 2016.
Contractor Eiffage Rail Express (ERE), will finance, design, build and maintain the infrastructure for 25 years. In exchange, ERE will receive contribution from the local authorities and RFF during the construction work. During the operating phase, it will also receive an allowance coming from the state to compensate the investment made, and from RFF to cover the costs related to line maintenance and renewal.