alert back ban banned caution entry exit go no plate prohibited road sign signs street traffic transport warning way chinese clever knowledge letter mandatory nonsence roadsign rule rules stop stopped strange ting understand understandable auto bus buses busses car minibus post prohibitory pylon roadsigns transportation travel city cityscape street car town tram tramway circle crossing hoop hula oval pedestrian ring toy walker yellow beware danger drive safety security vehicle animal black cat civilisation nature shape square wild dog elephant ahead construction orange sundtraffic us usa work