After the Madrid train bombings of 11 March 2004, hundreds of people queued at hospitals and mobile blood-donation units. The mobile unit at Puerta del Sol could not process the crowd, so the city provided buses to take waiting donors to the regional transfusion centre. Offers of blood met the immediate requirement in about ninety minutes, and authorities asked people to stop arriving directly at hospitals.
This was a queue to give rather than receive a scarce resource. Goodwill exceeded the capacity of one collection point, requiring the line itself to be moved elsewhere. In an emergency, numbers of donors are not enough; the ability to admit, collect, test and store donations in sequence is also part of the response.