Which of the following is the biggest challenge in developing a successful smart city project?

Can free public transport reduce air pollution in cities? Why? Please comment.

Which is the main challenge of mass tourism for European cities?

Which is the main challenge of mass tourism for European cities?

Since 2008, the number of tourists visiting European countries rose incredibly (http://bit.ly/2BHOCDt). Obviously, this steep increase in numbers had consequences and not always positive. For instance, certain locations (e.g. Barcelona, Venice Amsterdam and Rejkjavik) are suffering from a strong tourism overcrowding. What do you think is the main challenge that this steep increase brings for cities (e.g. Venice and Barcelona) targeted by mass tourism?

What are the main challenges concerning European cultural heritage?

Having a Retail Policy commonly brings certain benefits, which one do you think is the most important for cities, and why?