This comes from simple fluid dynamics. When a fluid is forced into a narrower pi...

kazinator on Sept 10, 2014 | parent | context | favorite | on: Bike lanes have sped up car traffic in New York Ci...

This comes from simple fluid dynamics. When a fluid is forced into a narrower pipe, it goes faster. (Venturi also tells us there is a drop in pressure, but it's not clear how this advanced aspect is applicable here.)