It's virtually impossible to ride around on a public bus during the summer without having someone crack open a few windows. At the same time, open windows--and air conditioning, which is present on less than 5% of inter-city vehicles worldwide--reduce fuel efficiency and don't even provide enough cool air to all passengers. As it turns out, this fuel/energy-efficiency conundrum can be fixed with a simple design modification, according to Sunil Kale, a professor of mechanical engineering at the Indian Institute of Technology in Delhi, India.
After Kale and his team conducted an aerodynamic study of fluid flow in buses, they found that passengers near the aisle don't receive any cool air from open windows, while passengers in the front only receive air from the rear of the bus. But by adding a wide vent at the front and back of the bus, or by adding roof vents, the "comfort zone" of cool air is expanded from 11% of the vehicle to over 50%. The vents also reduce drag, so fuel is conserved. That in turn could mean that public transportation ticket prices are kept down.
It's a simple fix, and one that could provide much relief to passengers. As fuel prices increase, the number of bus passengers probably will as well. And since buses are already the primary means of commuting within and between cities worldwide, any improvements, however small, are welcome.