Is by allowing complex systems to develop by creating a solid foundation. Small trade needs small production and basically looks like a fleemarket. Those are especially healthy if they also have new products build or created by small one or several persons companies.
Therefore it needs a fine by easy to understand and run legal company background for one or few person companies with small turnovers. It needs places to find a buyer from online platforms to market places and cheap ways to get there with the products.
No train can also carry even a standard one cubic meter case of goods. Markethalls hardly ever have enough parking lots or easy to register online pages to get a spot and even cheap small trucks miss fuel efficient drive trains with large amounts of gears to keep engine turns low on long steady stretches of travell.
Creating a fine small business environement in a developed nations means intelligent infrastructure investements that will benefit every citizen exponentially and creates a lot of movement.
Planning is even more important in areas in which millions live and have already a car enabling them to actually use it, trains are already packed and centers are crowded only by innefficient ways of space use.