Based on current knowledge, a slight gauge widening on straight track and a slight gauge tightening on tight curves might actually be more beneficial – whi

Based on current knowledge, a slight gauge widening on straight track and a slight gauge tightening on tight curves might actually be more beneficial – while trains don't have differentials, they normally (BART and some streetcar systems excepted) use conical wheels Right, BART got the track gauge wrong when they were using flat wheels. Instead of self-centering the wheels got dragged down the track. This went on for forty-odd years which is how BART earned its reputation for being so damn noisy.