When an emergency arises in a large crowd, the bystander effect dictates that your probability of getting help decreases despite plenty of onlookers. The solution? Pick a specific person from the crowd and explicitly command him or her to dial 000 instead of just yelling for someone to call for help.
Photo by vonderauvisuals.
The probability of help has often appeared to be inversely related to the number of bystanders; in other words, the greater the number of bystanders, the less likely it is that any one of them will help. The mere presence of other bystanders greatly decreases intervention. In general, this is believed to happen because as the number of bystanders increases, any given bystander is less likely to notice the situation, interpret the incident as a problem, and less likely to assume responsibility for taking action
You've probably heard of this idea before, and you may also have heard similar advice for getting help. One reddit user helpfully suggested picking out a specific characteristic when referring to someone ("you there in the red shirt!") to avoid any confusion.