Mopeds driving on public pathways

There seems to be alot of mopeds driving along the public pathway. There are no signs to say public pathways and what it can and cant be used for ? Lately its turning into another road for mopeds to take shortcuts across the estate. Also alot of mopeds kept in back gardens causing air pollution. We have enough pollution from cars but now have to put up with MTO with mopeds in back gardens causing noise and pollution. Is there no law now about changing culture of mopeds and pollution? Elderly and Children cant walk safely on public paths and petrol fumes in back gardens does this mean we have to keep are windows shut at home because we have not air quality?