Choosing a Tram Route: An Experience in Trading-Off Constraints

Trading-off is a familiar element in requirements practice, but it generally assumes a set of independent requirements competing for resources. Choosing a tram route depends instead on trading-off competing pressures from stakeholders and other constraints, such as cost/benefit, buildability, safety, and disturbance to townscape, parks, wildlife, heritage, and housing, in a way that satisfies a public inquiry. There is no perfect way to do this, but several simple techniques and rules- of thumb can be combined to do much better than seems to be usual. The approach adopted on this project consists of triage followed by evaluation. This splits the route into independently prioritisable partial routes. These are scored using hierarchically weighted critieria.