since the late 1980s, the saudis have been particularly energetic in catering to the needs of pilgrims. in 1988, a us$15 billion traffic improvement scheme for the holy sites was launched. the improvement initiative resulted partly from iranian charges that the saudi government was incompetent to guard the holy sites after a 1987 clash between demonstrating iranian pilgrims and saudi police left 400 people dead. a further disaster occurred in 1990, when 1,426 pilgrims suffocated or were crushed to death in one of the new air-conditioned pedestrian tunnels built to shield pilgrims from the heat. the incident resulted from the panic that erupted in the overcrowded and inadequately ventilated tunnel, and further fueled iranian claims that the saudis did not deserve to be in sole charge of the holy places. in 1992, however, 114,000 iranian pilgrims, close to the usual level, participated in the hajj.