Public transport primarily refers to what kind of system?

Public transport primarily refers to shared transportation systems that provide a service for the general public. This type of system is designed to move large numbers of people efficiently and often includes buses, trains, subways, trams, and ferries. Shared transportation facilitates access to various destinations within urban areas, as well as reduces the need for individual car ownership, thereby decreasing traffic congestion and environmental impact.

The emphasis on "shared" in public transport is key, as these systems are available for use by all members of the community, making travel more accessible and affordable than private transportation options. Public transport can also contribute to urban sustainability by promoting energy-efficient travel patterns and reducing the carbon footprint of urban mobility.

In contrast, the other options do not relate to transportation systems: informal housing refers to unplanned or unofficial settlements; illegal settlements denote areas that are not authorized for habitation; and sanitation systems concern the removal of waste and provision of clean water, which is unrelated to the movement of people. Understanding the concept of public transport as a shared system is crucial in urban geography, particularly when discussing efficiency, urban planning, and sustainability.