From the Howard County, Maryland blog Tales Of Two Cities: Love Thy Neighbor
An almost perfect example of how to respond to pure free-riding problems, establish exclusion. Phase 1 paid for a road through their neighborhood which connects to a future Phase 2 development. Phase 2 comes along, and cannot come to terms with Phase 1 about paying for this local road (owned by a homeowners association, apparently, and thus is fenced out.

A few weeks ago I received an email from a Tales of Two Cities reader about a turf war going on between the residents of the Legacy at Ellicott Mills Phase 1 and Phase 2. The conflict between the two active adult communities has escalated to the point where the Phase 1 residents have now gated off their community from Phase 2, denying Phase 2 residents direct access to Route 104.

There is a fair solution to this problem.