According to the government, the line will transport more than 300,000 people a day and greatly reduce traffic congestion in the city's south and west.
Infrastructure concerns heightened last week when an elevated bicycle track collapsed into the sea, killing at least two people.
The incident prompted Rio mayor Eduardo Paes to return early from a visit to Greece for the Olympic torch lighting ceremony. Upon his arrival he described the accident as "unacceptable" and promised a full investigation.
SECURITY
The government has said it will deploy some 38,000 armed forces during the Games, backed up by 48,000 police and firefighters. The security operation is about twice the size of that used for the London Games in 2012.
Despite a commitment to ensuring the safety of athletes, officials and tourists, the government last month cut its Olympic security budget by 550 million US dollars.
Officials said the move would mainly impact investments that are not directly related to the Games, such as an urban pacification unit within the Mare shanty town complex in Rio's north.
Plans to establish the unit before the Games have now been postponed to an undefined date.
Late last year the government announced it was liaising with international intelligence agencies to quell the threat of terrorist attacks during the Games.
POLLUTION
Earlier this month IOC chief Thomas Bach guaranteed the Games would be safe for sailing events despite concerns about water quality in Rio's Guanabara Bay.
The Rio government has admitted it won't be able to meet a 2009 pledge to reduce pollution in the bay by 80% ahead of the Games.
But officials say a vast network of nets, known as eco-barriers, have been strategically placed to prevent rubbish and waste entering the bay.
A fleet of eco-boats will also be used to scoop up trash from the water's surface.
Concerns have also been raised about water quality at the Rodrigo de Freitas lake, which will host rowing and canoeing events. The government said a cleanup operation of the lake had ensured it will meet international standards for the events.
LEGACY
As part of Rio's Olympic legacy pledge, many venues built for the Games will be turned into public schools, sports facilities and leisure centers.
Organizers say the Games will improve the quality of life for Rio's citizens through infrastructure works like new public transport links and better waste management.
In addition, thousands of people will benefit from job training, creating pathways for new careers.
According to IOC president Thomas Bach, the greatest legacy could be the healing of wounds inflicted by political and economic troubles.
"Despite the difficulties that Brazil faces, the flame is an eternal reminder that we are all part of the same humanity," Bach said during the torch-lighting ceremony in Greece last week. "That will be the great legacy for the Rio Games for Brazil and the world."
