Urbanization and an increase in the global population could add another 2.5 billion people to urban areas by 2050, with close to 90% of this increase in Asia and Africa (UNDESA, 2018).
When the UN Conference on the Human Environment ( Stockholm Conference) convened in 1972, the world’s population was around 3.8 billion. Today, the world’s population has more than doubled to 7.8 billion, with a projected increase to 9.9 billion by 2050 (PRB, 2020). Currently, more than 55% of the world’s population lives in urban areas. Urbanization and an increase in the global population could add another 2.5 billion people to urban areas by 2050, with close to 90% of this increase in Asia and Africa (UNDESA, 2018). Not surprisingly, predictions indicate transportation will double between 2005 and 2050, with vehicle numbers increasing three- or four-fold, particularly in developing countries. These numbers point to the importance of transportation systems that can service the needs of hundreds of thousands if not millions of people per day, who commute for work, school, commerce, and other reasons. However, moving so many people is no easy feat, especially in a sustainable manner.