Common sense says they must be useful in town or stationary/slow traffic,especially for pedestrians,but less so in fast moving stuff.The paradox here though is that most aftermarket cans are not that loud at low revs which is probably how you would be riding in slow conditions.The real noise comes on the open road when you wind it on.
The exception of course would be PH with his dry clutch,which will tell all and sundry that he is slowly coasting past that line of cars.
