Plans to develop the Southwest light-rail project in Minneapolis stalled again when an advisory committee postponed a vote on it. The bone of contention is whether to allow light-rail trains to run through a shallow tunnel to be built underground, or to keep them above ground and reroute freight traffic. The committee will take a week to explore other options. The delay also means the Metropolitan Council, the project's overseer, won't vote on the project until the middle of this month. The project has been 17 years in the making and could cost more than $1.5 billion.