Delhi’s Measures to Control Vehicular Pollution

Amid deteriorating air quality, the Delhi government has tightened vehicular pollution controls to curb emissions from road transport. As part of these measures, private vehicles registered outside Delhi that do not comply with Bharat Stage (BS) VI emission norms have been barred from entering the Capital. In addition, vehicles without a valid Pollution Under Control Certificate (PUCC) are also restricted from entry.

Overview of Bharat Stage (BS) Emission Norms

Bharat Stage (BS) emission norms are India’s vehicular emission standards, designed to regulate air pollutants released by motor vehicles. These standards are aligned with European (Euro) emission norms and prescribe progressively stricter limits on pollutants through the adoption of cleaner fuels and advanced vehicle technologies. India has steadily upgraded these norms to address rising concerns over air quality and public health.

Institutional Framework and Objectives

The BS emission norms are framed by the Ministry of Environment, Forest and Climate Change (MoEFCC) and implemented by the Central Pollution Control Board (CPCB). The primary objective of these norms is to control emissions of carbon monoxide, hydrocarbons, nitrogen oxides, and particulate matter, which are major contributors to urban air pollution.

Evolution of Bharat Stage Emission Norms in India

In 1999, the Supreme Court of India mandated that all vehicles sold in the country must comply with Euro I or BS I standards, also known as the India 2000 standard. India subsequently progressed from BS I in 2000 to BS IV by 2017. In a major policy decision, the country skipped BS V and directly implemented BS VI in April 2020, resulting in a significant tightening of emission limits.

Further strengthening the regime, BS VI Phase-II norms were introduced in April 2023, making Real Driving Emissions (RDE) testing mandatory to ensure that vehicles meet emission standards under actual on-road conditions. The government is now planning to introduce BS VII emission norms by 2026–27 to further align India with global standards.

Delhi’s Early Adoption of Stricter Emission Norms

Delhi has a mixed fleet of vehicles conforming to different BS standards because it adopted stricter emission norms much earlier than the rest of the country in response to severe air pollution. The city implemented BS II norms in 2001, BS III in 2005, and BS IV in 2010, well ahead of nationwide timelines.

Key Features of BS VI Emission Norms

The BS VI emission norms impose substantially lower emission limits compared to earlier standards. Under BS VI, petrol vehicles are required to reduce nitrogen oxide emissions by about 25 percent, while diesel vehicles must reduce hydrocarbons and nitrogen oxides by around 43 percent, nitrogen oxides alone by 68 percent, and particulate matter by 82 percent.

Additionally, the sulphur content in fuel has been reduced from 50 mg/kg under BS IV to 10 mg/kg under BS VI, enabling the effective use of advanced emission-control technologies.

Why Older Vehicles Are More Polluting

Older vehicles tend to emit significantly higher levels of pollutants due to outdated technology and engine deterioration. Pre-BS IV vehicles lack advanced exhaust after-treatment systems such as diesel particulate filters and selective catalytic reduction systems, which are essential for controlling fine particulate matter and nitrogen oxides.

As vehicles age, engine wear, poor fuel–air mixing, and ignition system degradation lead to incomplete combustion. Combined with high mileage and inadequate maintenance, these factors result in much higher real-world emissions compared to newer BS VI-compliant vehicles.