The project would involve rehabilitation and electrification of a 16.5km section of the Bucharest North - Urzceni line, with a new 2.5km branch from Odăile to the airport at Otopeni.
A previous tender for the study in 2016 was cancelled after failing to attract any bids.
A budget of Lei 2.7 ($US 710,000) has been set for the study, which is expected to take 14 months to complete.
The deadline for submission of bids is April 12.
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