1. Road density: Road density indicates the length of roads per unit area, which is important for assessing transportation infrastructure. While it can be influenced by urbanization, it is not a direct measure of the urban population.

2. Numbers of business complexes and shopping malls: Although the presence of business complexes and shopping malls can indicate commercial development, they are not direct measures of urbanization. Urbanization involves the overall growth of cities and towns, including various aspects such as population, infrastructure, economic activities, and social and cultural development.

3. Percentage of urban to total population: This is the most commonly used indicator to measure urbanization. It calculates the proportion of people living in urban areas, typically defined by certain population density or specific administrative criteria, relative to the total population of the country. This metric helps in understanding the demographic shift from rural to urban areas, as well as the pace and scale of urban growth within a nation.

4. Occupational structure of the population: While the occupational structure of the population can provide insights into the economic activities within an area, it does not directly measure urbanization. 

Other metrics, such as road density and the number of business complexes and shopping malls, are not direct measures of urbanization. While they may reflect certain aspects of urban development, they do not provide a comprehensive view of the urbanization process so option 3 is correct.