When the lead crew reached the circular crater that had been gouged in the dirt spur the day before by a steam shovel, the foreman blew on a whistle.

NPR: Excerpt: 'Legends'

Riding through the streets of the Condesa neighbourhood, for example, you encounter roving marimba players and the sweet potato vendor who pushes around a mobile oven with an ear-piercing steam whistle to herald his arrival.

BBC: Cycling the Aztec way