Since the 1970s, research into social networks has focused primarily on the types of ties developed within residential environments. Bonding ties, common of tightly knit neighborhoods, consist of connections that provide an individual with primary support, such as access to income or upward mobility among a neighborhood organization. Bridging ties, in contrast, are the ties that weakly connect strong networks of individuals together. A group of communities concerned about the placement of a nearby highway may only be connected through a few individuals that represent their views at a community board meeting, for instance.