At a major intersection in Jakarta, Indonesia during a recent morning rush hour, a low rumble permeates the sticky air. Dozens of motorbikes and scooters idle impatiently at a stoplight. As the light turns green, the rumble crescendos into an ear-splitting drone as the two-wheelers accelerate away. This scene plays out all day, every day at major intersections across South-East Asia, where motorized two-and three-wheelers, such as motorcycles, scooters and tuk-tuks, are the transport of choice for many. Over 80 per cent of households in Indonesia, Malaysia, Thailand and Viet Nam, for example, own motorcycles. In the six largest economies of the Association of Southeast Asian Nations (ASEAN), sales of motorcycles and scooters reached over 13.7 million units in 2019. Only China and India saw more sales. But that is becoming a major problem. Along with being noisy, the mushrooming number of conventional motorcycles and scooters is driving up energy consumption, air pollution and greenhouse gas emissions.