what does this means " design a device that stimulates a system for eco friendly public transport "
Imagine that bicycles do not exist. If you now invented the bicycle it could be considered an "eco friendly" method of transport as there are no fuels or emissions. People usually forget about any ecological harm that comes from mining and refining to form the base materials that objects are made from.
"Public transport" usually means something on a larger scale though. A bus, train, and subway are modes of public transport.
"A device that stimulates a system" is vague. You could design a software application that makes it easy to determine what train/bus/subway route will quickly and efficiently get you between several points. That could stimulate the system.
You could also invent an algorithm to solve the classic "traveling salesman" problem. That would lead to a lot of stimulation.