GLASGOW, Scotland — A group of nations and companies has announced plans to make the switch to emissions-free cars by 2040 and by no later than 2035 in leading auto markets. The announcement was made Wednesday on the sidelines of the U.N. climate conference in Glasgow. It was backed by countries including Canada, Chile, Denmark, India, New Zealand, Poland, Sweden, Turkey and the United Kingdom. Ford, General Motors, Mercedes Benz and Volvo, as well as several states and cities in the United States and elsewhere, signed the plan. Some companies, such as Volvo, already have even earlier targets to phase out combustion engines. Separately, a number of countries are pledging to phase out the use of trucks and buses with internal combustion engines. Companies involved in road haulage are signing up, including delivery giant DHL, truck-maker Scania and Dutch brewer Heineken.