In Nairobi's congested streets, the almost imperceptible hum of electric motorbikes is increasingly replacing the roar of their petrol-powered counterparts. The war in the Middle East, launched by the United States and Israel in February, has had the unlikely consequence of boosting green vehicles across Africa, especially in countries such as Kenya that are heavily dependent on fuel imports. "Boda-bodas" -- the name given to motorbikes in Kenya -- are a vital part of the economy in the east African nation, used to transport everything from people to groceries to furniture.