Armed robberies have gotten so common aboard buses in Mexico City that commuters have come up with a clever if disheartening solution: Many are buying fake cellphones, to hand over to thieves instead of their real smartphones.

Costing 300 to 500 pesos apiece — the equivalent of $15 to $25 — the “dummies” are sophisticated fakes: They have a startup screen and bodies that are dead ringers for the originals, and inside there is a piece of metal to give the phone the heft of the real article.

That comes in handy when trying to fool trigger-happy bandits who regularly attack the buses, big and small, that ferry people from the poorer outlying suburbs to jobs in the city center.