Indian street food is popular in the United States, but relatively little of it is sold from food trucks. The mismatch is between how the food is made and how a mobile kitchen is built.
Open frying is the central technique
A large share of the repertoire depends on a wide, open pan of hot oil at a working depth, with the cook watching and adjusting constantly.
American mobile kitchens use enclosed commercial fryers with baskets and thermostats, which are excellent for uniform items and poorly suited to the free-form frying that pakoras, puris and vadas require.
Ventilation and fire suppression requirements in a confined truck also make an open pan of oil a difficult proposition compared with a fixed installed unit.
Assembly needs counter space more than cooking space
Chaat and similar dishes need many small containers within reach of one person, which is a layout problem rather than a cooking one.
Truck interiors are organized around appliances along the walls with a narrow aisle. The wide shallow working surface an Indian vendor uses does not fit that geometry easily.
Freshness windows fight the service model
A truck typically travels to a location, serves a lunch rush and moves on, which favors items that can be batched and held.
Much Indian street food is at its best within a minute of assembly, so batching either degrades it or forces production rates that a two-person crew cannot sustain.
Items that hold well, such as rolls, wraps and rice bowls, are exactly the Indian street items that have succeeded on American trucks.
Ingredient supply adds a further step
A truck operator needs reliable resupply of specific flours, fresh curry leaves, chutney ingredients and fried components, which usually means a dedicated relationship with an Indian wholesaler rather than a standard broadline supplier.
Commissary rules in many US jurisdictions also require prep to happen in a licensed fixed kitchen, adding a location and a cost that a single-item Indian cart would not carry at home.
The formats that have worked
Kathi rolls, dosas made on a large flat top, and rice or bowl formats have all translated, because each maps onto equipment a truck already has.
The pattern is consistent: Indian street food succeeds on American trucks where the cooking is a griddle or a wrap station, and struggles where it depends on an open fryer or fast hand assembly.