Short answer: in most urban settings, no—you usually do not need a special bag for a normal trash can. A regular trash liner that fits the can is fine. The important thing is that the liner fits properly, does not hang over the sides too much, and is strong enough not to tear when the bin is emptied.
That said, “urban” covers a lot of different situations. If you mean a city-issued curbside cart, many municipalities do not require any particular bag, and some even prefer no bag for certain automated collection systems. Check your city’s waste department rules. For shared apartment, office, or building bins, the property manager may have its own policy—often just a standard heavy-duty liner to keep the bin clean. For public street trash cans, residents usually do not line them; city crews use their own heavy-duty bags.
If your city has an organics or food-waste program, that specific bin may require certified compostable bags and may prohibit regular plastic liners. Recycling is different too: many programs ask you not to bag recyclables at all. So for a regular urban household trash can, use a normal liner sized to the can, avoid overfilling, and follow any posted building or municipal instructions. When in doubt, check your local waste authority’s website or ask your building manager—the rule is usually local, not universal.