The Philippines is set to have its first subway system as part of a 3.6 trillion peso (S$100 billion) three-year development programme that President Rodrigo Duterte hopes will kick off a "golden age of infrastructure".

The subway itself will be the most expensive of all the planned infrastructure projects, at a cost of 227 billion pesos.

The central section of the underground railway system will have 13 stops spanning about 25km. It will cut vertically across metropolitan Manila, from Quezon City in the north to the main airport in the south, and two key financial districts in between - Makati and Ortigas.

The trains are expected to carry around 300,000 passengers a day.

The project was first broached under then President Benigno Aquino in 2014, but set aside the following year as Mr Aquino had less than a year left in his six-year term. The government had decided to focus instead on eight ongoing rail projects and two "bus rapid transits".

Other planned projects

NORTH-SOUTH RAILWAY / SOUTH LINE Rehabilitation of 653km of railway from Manila to the Bicol region. Value: 151 billion pesos (S$4.2 billion). NORTH-SOUTH RAILWAY / NORTH LINE Construction of railway linking Manila and a special economic zone in Pampanga province, where a 50 billion-peso "sports city" is also being planned. Value: 225 billion pesos. MINDANAO RAILWAY A 2,000km railway linking key cities in the war-torn southern island group of Mindanao, including President Rodrigo Duterte's home city of Davao. Value: 121 billion pesos. DAVAO AIRPORT Upgrade and expansion of Davao's airport, a key gateway to the southern Philippines. Value: 40.6 billion pesos. METRO MANILA BUS RAPID TRANSIT A network of buses and terminals to supplement metropolitan Manila's mass rail network and ease the capital's traffic. Value: 37.8 billion pesos.

But Mr Duterte is determined to finish the subway project as a legacy of his administration.

Last week, his economic managers unveiled an ambitious infrastructure spending boom with the catchphrase: "Build! Build! Build!"

The "Mega Manila Subway" tops the list of projects the government plans to start in the next three years. The others are railways connecting Manila to provinces in the north and south, a 2,000km railway in the war-torn southern island of Mindanao, a bus rapid transit in the capital, a new airport in Mr Duterte's home city of Davao, and a "sports city" in a special economic zone that used to be a US military base.

"This is a very ambitious project. Give us your trust, give us your confidence, we will build it," Transportation Secretary Arthur Tugade said last week. He added that the government hopes to begin building the underground railway in the fourth quarter of 2020, and have the first train rolling by 2024, two years after Mr Duterte steps down.

But that may be too optimistic.

Analysts say construction of the subway may worsen Manila's already horrendous traffic congestion, as it will likely lead to lengthy road closures that may last for about 10 years. Manila's perennial flooding problems may also pose a problem, they add.

"Unfortunately, our changing governments, they do not have institutional memory," said Mr Felino Palafox Jr, a leading architect and urban planner.

"There's a very long time between concept, commitment and completion. It takes several generations," said Mr Palafox, suggesting that construction of an underground railway is unlikely to start till 2021, and it may take at least 10 years to finish.