A lighting system has at least one luminaire (1) for illuminating a thoroughfare (10). At least one sensor (11,12,13) detects that a fallen object (30) may be at least partially blocking said thoroughfare (10). A traffic flow monitor (11,12,13) monitors traffic flow along said thoroughfare (10). The light output by the luminaire (1) is controlled to be of a first pattern in accordance with a determination that a fallen object (30) is at least partially blocking said thoroughfare (10). The light output by the luminaire (1) is controlled to be of a second pattern in accordance with the traffic flow monitor (11,12,13) determining that traffic is flowing along said thoroughfare (10).