As transport commissioner, Janette Sadik-Khan faced down critics to transform New York with 400 miles of cycling routes, a bike share scheme and the remodelling of Times Square. Any city can do it, she tells Peter Walker

Public advertising is pollution and it needs to be curbed. So insists a new policy from Barcelona, which will substantially cut back on how much advertising City Hall permits in public places. In a bid to make Barcelona a more attractive, less aesthetically cluttered place, street advertising in the city will be reduced by 20 percent in July 2016.

What makes some places succeed while others fail? In evaluating thousands of public spaces around the world, PPS has found that successful ones have four key qualities: they are accessible; people are engaged in activities there; the space is comfortable and has a good image; and finally, it is a sociable place: one where people meet each other and take people when they come to visit. PPS developed The Place Diagram as a tool to help people in judging any place, good or bad:

The Habitat Exchange is a venue for the dissemination and discussion of best practices, action plans and other tools relevant to the pursuit of ecologically sound and socially equitable urbanization. The Habitat Exchange aims to be a portal for learning and collaboration and we welcome ideas for future partnerships.

In the old photograph, a lonely farmhouse sits on a rocky hill, shaded by tall trees. The scene looks like rural Maine. On the modern street, apartment buildings tower above trucks and cars passing a busy corner where an AMC Loews multiplex faces an overpriced hamburger joint and a Coach store. Multimedia Interactive Map How Manhattan's Grid Grew Slide Show Manhattan's Master Plan Arts Twitter Logo. Connect With Us on Twitter Follow @nytimesarts for arts and entertainment news. Arts Twitter List: Critics, Reporters and Editors Arts & Entertainment Guide A sortable calendar of noteworthy cultural events in the New York region, selected by Times critics. Go to Event Listings » Readers' Comments Readers shared their thoughts on this article. Read All Comments (135) » They are both the same spot. Not so long ago, all things considered, the intersection of Broadway and 84th Street didn't exist; the area was farmland. "The Greatest Grid: The Master Plan of Manhattan, 1811-2011," now at the Museum of the City of New York, unearths that 1879 picture of the Brennan Farm among other historic gems. The show celebrates the anniversary of what remains not just a landmark in urban history but in many ways the defining feature of the city.

n 2011, the World Bank initiated the Partnership for Sustainable Cities, a group of leading urban actors with a mission to collaborate on city development around the world and foster city-led sustainable development. This synthesis paper, Building Sustainability in an Urbanizing World, is a product of the partnership's early discussions. In this paper, members of the partnership have collaborated to identify and analyze the issues that guide their work together. The report summarizes the sustainability issues faced by cities and points toward the road ahead. It reviews successes in policy as well as investment and discusses what is needed to reach out to the rapidly growing cities of the developing world and make them effective users of existing knowledge. Examples of programs established by the partners are described in both the text and the Annexes. This report aims to be useful to the partners who contributed with knowledge and experiences, to cities who may benefit from an honest discussion of what works and what needs improvement, and to businesses and development practitioners entering the wide world of sustainable cities.

The report "Innovation and the City" [PDF] is an important addition to our knowledge of urban policy innovation. It summarizes the results of a six-month research effort by policy researchers at New York University's Wagner School of Public Service and the New York-based Center for an Urban Future. The research team interviewed over 200 experts (including our own Emily Badger) and surveyed more than 120 policy innovations. (I should disclose here that I am Global Research Professor for the NYU School of Continuing and Professional Studies).

It's a mid-rise building that encompasses nearly an entire city block, usually developed over a surfacing parking lot or under-utilized former industrial site. There are countless more examples, even at the townhouse level (two examples from Minneapolis' downtown: here and here). Certainly, the loss of a parking lot is nothing to shed a tear over, but this building typology, which currently represents our American view of 'urban', presents itself as somewhat problematic.

THIS blog often makes the argument that Britain's planning laws all too often restrict and prevent investment which might create economic growth. It is worth remembering occasionally that things were once much worse. For proof of that, see this fascinating post on Birmingham's economy in the 1950s and 1960s, by Henry Overman, of the LSE's Spatial Economics Research Centre. It's worth reading the whole thing, but a cut down version of the post is copied below:

Informal areas have largely been responsible for absorbing most of Egypt's growing urban population for the past 30 years. But most Cairenes didn't notice these areas - or ashweyat, as the areas with red-brick buildings and narrow, unpaved streets are loosely called - until the Ring Road was built around the formal city limits about 10 years ago. The road exposed neighborhoods that many residents had never seen before, showing them for the first time that formal Cairo had been completely surrounded by kilometer after kilometer of informal building.

Thirty years ago, Curitiba, Brazil unveiled a master plan to address urban issues with environmentally-friendly public transit and social programs. FRONTLINE/World Fellow Tim Gnatek took to the busses, walkways and streets of the now world-renowned city for a second look at what urban planners and environmentalists around the globe point to as a world model.

Density. For planners and urban designers helping to create transit-oriented developments (TODs), density is the crucial factor in achieving a critical mass for ridership and a mixed-use walkable environment that will entice people out of their cars. In many cases if planners can't reach that threshold of density than transit is the baby that gets thrown out with the bath water.

In a piece called The Beauty of Urban Planning from Space, the Sustainable Cities Collective highlights views from space of uniquely designed street pattern designs in various cities around the world. There are ten examples that illustrate the zenith of urban planning. As attractive as the street patterns are, they highlight the inevitable inability of designers, or anyone else for that matter, to influence much more than small changes in the overall urban form.

Getting the right city density - generally expressed in the US as people per square mile or homes per acre - to support sustainable and pleasant living is one of the trickiest problems we face as we address the future of our communities. The typically low densities of suburban sprawl built in the last half of the 20th century, despite their popularity at the time with a considerable share of the market, have been shown by a voluminous body of research to produce unsustainable rates of driving, carbon emissions, pollution. stormwater runoff, and adverse health impacts.

The City 2.0 website is a platform created to surface the myriad stories and collective actions being taken by citizens around the world. We draw on the best of what is already being discovered by urban advocates and add grassroots movers and shakers into the mix. What's emerging is a complex picture of the future city--a place more playful, more safe, more beautiful, and more healthy for everyone. http://www.ted.com/pages/tedx_tedxcity

Spain may be facing significant economic and political challenges these days, but Barcelona's city-building remains one of the best models in the world. Few cities inspire my thinking more. Thus it was a fitting location for the second Global Smart City Expo/Congress, and my invitation to speak was a good excuse to return, and share some of the best "steal-able" lessons. The Congress may have talked a lot about urban technologies, but Barcelona reminds us how smart the fundamentals are when it comes to making great cities.

Global Urbanization surveys essential dimensions of this growth and begins to formulate a global urban agenda for the next half century. Drawing from many disciplines, the contributors tackle issues ranging from how cities can keep up with fast-growing housing needs to the possibilities for public-private partnerships in urban governance. Several essays address the role that cutting-edge technologies such as GIS software, remote sensing, and predictive growth models can play in tracking and forecasting urban growth. Reflecting the central importance of the Global South to twenty-first-century urbanism, the volume includes case studies and examples from China, India, Uganda, Kenya, and Brazil. While the challenges posed by large-scale urbanization are immense, the future of human development requires that we find ways to promote socially inclusive growth, environmental sustainability, and resilient infrastructure. The timely and relevant scholarship assembled in Global Urbanization will be of great interest to scholars and policymakers in demography, geography, urban studies, and international development.

On my flight home from California last week, I took the photo above. It's not the greatest photo, but I captured the image to illustrate the edge of suburban sprawl in some place or other, I'm not sure where. Reviewing it later, one of the things that struck me is that the development protruding onto the landscape in the photo is actually relatively high-density, as single-family residential development goes. Those are small lots, and my very wild guess is that we could be looking at 15-20 homes per acre, enough to pass the density prerequisite of LEED for Neighborhood Development and maybe even earn a density point or two.

The first time I heard the term 'historic compromise' used with respect to parking policy in Zurich, I was taken aback by the grandiosity of the term. But as I learned, this term is more than apt in light of the contentious battles that ended in 1996 with a brokered agreement over parking. Even in a city known for its progressive transportation policies, a 'historic compromise' was needed to reverse the corrosive effect that parking was having on the city.

Income inequality has been on the rise in America for several decades now (for complicated reasons that we'll let Richard Florida explain), and the trend has been starker in some regions of the country, and in some cities, relative to others. Now, however, we are also beginning to see - all the way down to the neighborhood level - that America's growing gap between the rich and poor is also affecting where (and with whom) we live.