Simon Jessop and William James, respectively.

GLASGOW (Reuters). Six of the largest automakers in the world will announce Wednesday that they are committing to phasing-out fossil-fuel vehicle production by 2040. This is part of global efforts reduce carbon emissions.

However, sources close to the content of the pledge claim that there are some major carmakers such as the top two in the world. Toyota Motor (NYSE.) Corp and Volkswagen AG(OTC:) have yet to sign up, as has China, Germany, and the United States. These events highlighted the obstacles that must be overcome to achieve a zero emission future.

Volvo Sweden and Ford America (NYSE:) Daimler AG (DE): India’s Mercedes-Benz, China’s BYD and Jaguar Land Rover. Tata Motors (NYSE:) were expected to sign the climate pledge in Glasgow at the recent initiative to limit global warming to mid-century.

Volvo already has committed to becoming fully electric by 2030.

Britain is hosting the COP26 summit. Four new countries, including New Zealand, and Poland, have joined other countries already committed to ensuring that all new vehicles and cars are emission-free by 2040. 

This statement is made on the day that was dedicated to transportation at the conference.

However, it is questionable whether the pledge’s effectiveness has been questioned by China, which is the largest auto market in the world, as well as the United States, the largest economy in the world and second largest automobile market.

Sources claimed that the United States does not have to sign up for the pledge but key states such as California and New York, which are car-buying states, have done so.

A source in the auto industry said that some carmakers don’t like the idea of a pledge. It requires them to shift to expensive technology but does not require a similar commitment by governments.

Summer saw the European Commission propose a comprehensive ban on fossil-fuel cars by 2035. It was accompanied with the commitment to the charging infrastructure carmakers demanded.

World’s No. Stellantis was the world’s No. 4 carmaker.

Sources claim that Uber, a ride-hailing service (NYSE:), will be signing.

According to the British government, a declaration will be made by all companies (including Sainsbury’s Food Retailer) and other cities that are aiming at greening their vehicles fleets.

According to data from International Energy Agency, around 25% of global carbon emissions come from cars, trucks, ships and buses. The bulk of this comes from roads.