Zoning (the segregation of delimited uses into zones) has been a common urban planning practice for modern movement. However, from a current perspective, it is necessary to think of mixed economic activity areas, with activities that are compatible with each other, so as to guarantee the mixed nature of activities and minimise travelling, with the subsequent air pollution. The industrial regeneration of the metropolitan area implies improving the industrial platform implemented in the territory, particularly accessibility and services. The new economic and production situation requires:

• Improving the accessibility to public transport
• Ensuring railway connection for freight transport
• Fostering synergies between companies and universities
• Connecting the areas of economic activity with urban centres to guarantee the demand of activity

The challenges of the PDU in relation to the areas of economic activity need to be considered with a perspective that goes beyond the metropolitan area, in order to understand the system as a whole and its complexity. The main challenge is to ensure the all-inclusive renovation of obsolete industrial estates and improve the implementation and management of these areas in the territory.