How petrol motorbikes drive Hanoi's air pollution

The Vietnamese capital city has over 9.2 million registered vehicles by the end of 2024, including more than 1.1 million cars, according to statistics from the Department of Construction. Yet it is motorbikes that dominate both the roads and the pollution charts, with an additional 1.2 million vehicles from other localities enter Hanoi daily, making the situation worse.

Traffic activities are among the major contributors to air pollution, with pollutants including PM2.5, carbon dioxide, nitrous dioxide and sulfur dioxide, according to Hanoi's Department of Agriculture and the Environment.

A group of researchers, including Ngo Quang Khoi and Associate Professor, Dr. Hoanh Anh Le, mapped pollution hotspots across Hanoi using data from previous projects and air quality data collected from 10 stations in the city. The study, funded by the Vietnam National University in Hanoi, found the worst air quality along major roads like Ring Road 3 on the city's outskirts, where PM2.5 levels are nearly double the national safety limit.

Inside the inner city, motorbikes are the main culprits, flooding residential areas with toxic emissions, the study found. While cars contribute 9% of CO emissions, motorbikes release almost nine out of every ten units of this harmful gas. When it comes to particulate matter, motorbikes contribute 66% of PM emission, while cars contribute 13%.

The concentration of fine dust and CO emissions in Hanoi, from inner area (inside Ring Road 1) for outer areas. Graphics courtesy of Associate Professor, Dr. Hoang Anh Le

But the problem is not confined to Hanoi itself.

A World Bank report shows that two-thirds of Hanoi’s deadly fine dust pollution actually drifts in from outside the city, carried by winds from the Red River Delta and beyond. While transport accounts for 25% of local PM2.5, factories, power plants, burning crop waste and livestock farming all contribute to the toxic air.

The World Bank has recommended four key solutions: replacing gas-powered motorbikes with electric ones, switching cars to EVs, adopting stricter EURO 5 and EURO 6 emissions standards, and replacing diesel buses with clean-fuel models. Replacing motorbikes and cars with electric vehicles is seen as the fastest way to cut deadly fine dust.

But cleaning Hanoi's air will come cheap. The cost of a full transition is estimated at €1.56 billion (US$1.81 billion), according to the World Bank. And even then, experts warn that unless surrounding localities act too, Hanoi's efforts will not be enough. Without regional cooperation, PM2.5 levels in Hanoi are projected to fall just 20% by 2030, still nearly double the national limit.

Vietnam's government is now stepping in. Under a new directive, Hanoi will ban all gas-powered motorbikes from downtown streets by July 2026. Fossil-fuel cars will face restrictions from 2028, with a total ban on gas-powered private vehicles within Ring Road 3 by 2030.