Bay Area Rapid Transit (BART) is a public transportation system that serves the San Francisco Bay Area in California, United States of America. BART is one of the busiest rapid transit systems in the country, carrying over 400,000 passengers daily across its 112 miles of track and 48 stations. The system is owned and operated by the San Francisco Bay Area Rapid Transit District, a special-purpose district that was established in 1957.

BART has been a leader in decarbonisation efforts in the transportation sector, with a goal to reduce greenhouse gas emissions from its operations to net zero by 2050. The system has already made significant progress towards this goal, with a 90% reduction in emissions from its electricity use since 2013. BART's decarbonisation efforts are focused on three main areas: energy efficiency, renewable energy, and electrification of its fleet.

Energy efficiency is a key component of BART's decarbonisation strategy. The system has implemented a number of measures to reduce energy consumption in its stations and facilities, including the installation of energy-efficient lighting and HVAC systems, and the use of regenerative braking technology on its trains. BART has also implemented a corporate energy management program to track and manage its energy use, and has set a goal to reduce its energy consumption by 50% by 2030.

Renewable energy is another important component of BART's decarbonisation strategy. The system has entered into a number of corporate power purchase agreements (PPAs) to source renewable energy for its operations. In 2018, BART signed a PPA with Recurrent Energy for the purchase of 61.7 MW of solar energy from a new project in Central California. This PPA will provide BART with 25% of its electricity needs and is expected to save the system $200 million over the 25-year contract term.

BART has also installed its own renewable energy systems, including a 3 MW solar array at its maintenance facility in Hayward, California. This system provides about 5% of BART's electricity needs and has saved the system over $3 million in energy costs since it was installed in 2016.

Electrification of BART's fleet is the third component of its decarbonisation strategy. The system is in the process of replacing its aging fleet of diesel-powered trains with new electric trains. The new trains are expected to be more energy-efficient and will help BART to further reduce its greenhouse gas emissions. BART has also installed charging infrastructure for its electric buses, which are used for shuttle service at some of its stations.

BART's decarbonisation efforts have not only helped to reduce the system's environmental impact, but have also resulted in significant cost savings. The system's energy efficiency measures and renewable energy investments have saved it over $30 million in energy costs since 2013. BART's commitment to decarbonisation has also helped to position it as a leader in sustainable transportation and has earned it recognition from organizations such as the Sierra Club and the American Public Transportation Association.

In conclusion, BART is a public transportation system that serves the San Francisco Bay Area in California, United States of America. The system has made significant progress towards decarbonisation, with a goal to reduce greenhouse gas emissions from its operations to net zero by 2050. BART's decarbonisation efforts are focused on energy efficiency, renewable energy, and electrification of its fleet. The system has implemented a number of measures to reduce energy consumption and has entered into corporate PPAs to source renewable energy for its operations. BART's commitment to decarbonisation has not only helped to reduce its environmental impact, but has also resulted in significant cost savings.