The main objective of curfews is usually crime prevention.  Youth crime is a major and growing problem, often involving both drugs and violence. Particularly worrying is the rise of youth gangs who can terrorise urban areas and create a social climate in which criminality becomes a norm. Imposing youth curfews can help to solve these problems, as they keep young people off the street, and therefore out of trouble, and prevent them from congregating in the hours of darkness. Police in Philadelphia have found curfews effective in the prevention of gang violence: ‘the measure has been successful in helping to curb violent attacks by teen mobs that had severely injured several people in recent months, city officials said.’ 1  1. Associated Press, 2011,