I'd like to preface my comment by saying, I don't think my interpretation is in line with the intended meaning when it was written. However, it makes me think that people are being likened to chemical atoms. For a chemical reaction to occur, a "fruitful collision" has to occur between the two interacting molecules. Likewise with humans, for relationships to form and developed, chance meetings have to happen. These most often occur in areas of high abundance, such as crowds during the rush hour. Except in the song I always imagined the type of fruitful collision that would occur would be sexual in nature, hence he needs contact.
I'd like to preface my comment by saying, I don't think my interpretation is in line with the intended meaning when it was written. However, it makes me think that people are being likened to chemical atoms. For a chemical reaction to occur, a "fruitful collision" has to occur between the two interacting molecules. Likewise with humans, for relationships to form and developed, chance meetings have to happen. These most often occur in areas of high abundance, such as crowds during the rush hour. Except in the song I always imagined the type of fruitful collision that would occur would be sexual in nature, hence he needs contact.