A funicular is a specialized cable railway system designed to transport passengers or cargo up and down extremely steep slopes where traditional locomotives would lose traction. The system technically consists of two counterbalanced carriages permanently attached to opposite ends of a single haulage cable, which is looped over a drive bullwheel at the top of the track. As one car descends, its weight acts as a "counterweight" to help pull the other car up, significantly reducing the energy required for propulsion. Most modern funiculars utilize a single track with a "passing loop" (Abt switch) in the middle, where the cars move around each other using specialized wheels—one side having deep grooves to follow a continuous outer rail and the other being flat to glide over the rail switches without moving parts.