The traditional walking city generally has 100-200 persons per hectare (250-500 per acre) and is a compact 'pre-industrial' urban from in which activities are in close proximity and easily accessible on foot or with simple hand- or animal-drawn carts. Streets are often narrow and congested, and, apart from a small administrative core, functions are not segregated spatially. Walking is the primary form of transport, and may continue to be so in the core even after the city has evolved beyond that form.