Compared to an estimated congestion-caused loss of $6 billion every year, the annual mitigation would be worth $0.7 billion.

The city can save about VND245 trillion in 15 years by reducing traffic congestion with toll gates for cars entering its downtown area, said Lam Thieu Quan, director of the Innovative Technology Development Corporation (ITD), which suggested the plan.

The figure is derived from quantifying the benefits of less traffic congestion, he said. Traffic congestion is estimated to cost HCMC about VND140 trillion ($6 billion) every year through wasted time and fuel.

Once the toll gates start functioning, vehicles would travel 10 percent faster and each driver and passenger on the road would save about 12 minutes which would have otherwise been lost in traffic jams. That means each driver and passenger would save VND40,000 ($1.7) per day, or $10.6 billion in 15 years (2020-2035).

Quan said 10 percent of the city’s population use cars, while 80 percent use motorbikes. Motorbikes can also carry more people while taking up less space on the road compared to cars, so controlling car flows into downtown areas would be more effective than controlling motorbike flows, he added.

The suggested toll fees are VND40,000 ($1.7) for normal cars, VND50,000 ($2.2) for coaches and VND30,000 ($1.3) for taxis. Buses and prioritized vehicles like ambulances or firefighter trucks will pay no toll fee.

The toll fees could see the number of cars entering downtown reduced by 40 percent, said Quan. Within the first year of executing the plan, the number of cars entering downtown areas would be reduced by up to 49 percent during rush hours (6 a.m.-9 a.m. and 4 p.m.-7 p.m.), while the number of buses would increase by 9 to 15 percent. This would help people switch from using personal vehicles to using public transport, he said.

No form of punishment is currently envisaged for drivers who fail to pay the fees, but HCMC authorities would suggest punitive measures when the Ministry of Transport adjusts traffic laws in the future.

All the money collected from the toll gates would fund the development of public transportation, including new buses and bus stops.

Similar toll gates have been erected in countries like Sweden or Singapore before, Quan said. When Singapore applied a similar plan in 1975, the number of cars entering downtown Singapore reduced by 40 percent just a year later, he added.

The plan for the toll gates in HCMC received inputs from foreign consultancy that had advised the Swedish capital of Stockholm earlier on the same issue, Quan said.

This is not the first time ITD has proposed toll gates for cars entering downtown HCMC. In 2010, the city’s People’s Committee had accepted a proposal by ITD, but the plan was scrapped two years later because of opposition from experts and the general public.

At the end of 2016, the city’s People’s Committee requested the Department of Transport to work with ITD again to make adjustments to the plan as HCMC suffered ever-worsening traffic jams.

Earlier this month, the HCMC Department of Transport suggested that the city spends VND250 billion ($10.7 million) from the national budget to build 34 toll gates for cars entering the downtown area to reduce congestion and pollution. The toll gates are expected to be erected in Districts 1, 3 and the borders of District 5 and 10.

HCMC, the country's largest metropolis with 13 million people, has around 7.8 million motorbikes and about 750,000 cars, according to the city's police department.

Ngo Hai Duong, head of the road infrastructure development unit at the city Department of Transport, said car registrations in the city increased 15 percent in the first six months year-on-year and that of motorbikes by 6 percent.

"Without intervention, traffic congestion in the city downtown will get more serious," Duong said.

Earlier this year, a proposal drafted by the Ministry of Transport's Transport Development and Strategy Institute asked the city to restrict and eventually ban motorbikes from a number of downtown areas from 2025.

But legal and transportation experts have railed against the ban, calling it "hasty" and "impossible." The city officials later promised that motorbikes in the city would only be restricted and not banned.

The capital city of Hanoi has also prepared a draft plan to restrict entry to downtown areas via automatic toll fees.