You do still use (some) batteries for trolley buses, as they have to bridge gaps where the overhead wires are unavailable (roadworks etc). The overhead wires a

You do still use (some) batteries for trolley buses, as they have to bridge gaps where the overhead wires are unavailable (roadworks etc). The overhead wires are the biggest reason to avoid trolley buses. They're expensive to deploy and maintain, a visual eyesore, and constrain the bus network to predefined routes. Electric buses are a great improvement - At the expense of more batteries per bus and deployment of charging stations at depots/terminus, you avoid the wiring hassle entirely and have far more flexibility to change routes as required.