NEW DELHI—Inexpensive motorcycles and scooters will make up the largest group of new vehicles hitting the world’s roads in the next decade—and a rapidly growing share of those bikes will be electric, say manufacturers and analysts.

With auto sales slowing in the biggest developed markets, electric two-wheelers may soon have their moment. Hundreds of millions of them will likely be sold in places like India, China and other emerging markets, according to projections from the Energy and Resources Institute, a New Delhi think tank.

Gasoline-powered bikes still make up the bulk of two-wheeler sales, but companies like China’s Nasdaq-listed NIU Technologies and India’s Hero Electric Vehicles Pvt. Ltd. have begun offering reliable electric motorcycles and scooters at more affordable price points. Startups aiming to become the Tesla of two-wheelers are touting high-tech, sleekly designed models for less than $2,000.

An electric-motorcycle boom could launch a new generation of drivers who prefer electric vehicles, and may be more likely to choose electric cars once they can afford them, say analysts and executives.

Electric two-wheelers are already having an environmental impact, according to the International Energy Agency, a Paris-based energy watchdog. Electric two- and three-wheelers on the roads avoided more pollutants than all electric cars combined in 2018, the most recent year for which data is available, according to the IEA.