Marco Ponti Urban density, the environment, and mobility, Venezia SIET September 20th, 2013 Marco Ponti – Politecnico of Milan Urban density, the environment,

Marco Ponti Urban density, the environment, and mobility, Venezia SIET September 20th, 2013

Marco Ponti – Politecnico of Milan

Urban density, the environment, and mobility

A non-mainstream approach


1. What is a city?

In these notes, a city is instrumentally reduced to its density, for two reasons: the main one is that urbanization is growing, but densities are declining (the well-known “urban sprawl” phenomenon, even in the USA). The second reason is related to modal alternatives: below a certain level of density, the possibility of providing collective transport at reasonable costs declines, and individual mobility becomes dominant.

The available data are mainly related to the U.S. context, where the issue has been analyzed in more detail.


2. Common Wisdom: urban sprawl is hell for the environment

It increases the average distances travelled,generating more fuel consumption, also due to less use of collective transport.

3. The reality is far more complex: urban sprawl is good for your health, and for housing and retail prices

The impact on people of emissions is growing with density (the well known “canyon effect”), less building constraints lower house prices, and also the possibility of large retail stores lowers prices. Urban rent is reduced. Total CO2 emissions are not so certainly higher (see congestion in dense areas).






4. Common Wisdom: urban sprawl is hell also for mobility costs

Long commuting: average distances are higher, congestion is worse due to modal split (mandatory car use, a mode far more expensive for the users than collective transport).

5. The reality is far more complex: high density is good mainly for white-collars, and land rent

Congestion is in general worse in dense areas, travel times are not shorter, collective transport can serve only central, tertiary areas, and urban rent captures a large share of the benefits of collective transport.


6. “Polluters pay”: a sound principle

Of the polluting activities, road transport pays in taxes much more than other sectors burning fossile fuels, and anyhow much more than the social cost attributed by the EU to a ton of CO2, around 50€.

While the IPCC estimates the role of road transport in CO2 emissions to be around 25%, it assumes a target of reduction of only around 10%, given the high opportunity cost of reduction in this sector compared to others.(CO2 emissions are obviously also a proxy for other pollutants, for example NOX and particulates).The IPCC gives to modal change policies a very limited role.


7. ….But also “users pay” is a sound principle

Subsidies to collective transport is a poor tool for getting relevant changes in modal split (low cross elasticity). But in general subsidies are justified by distributive reasons.True, but in large cities, where collective transport is relevant, there are also strong regressive results: white collars, well served, are subsidized by “external” blue collars, that have to use super-taxed private cars given the low density of the “desire lines” that are dominant in low-density, disperse residences and job locations. And, as we have seen, land rent captures a large share of the benefits of subsidized transport.Better avoid subsidizing the more well-off…..


Factories

Commuting of “white collars”

Housing of “white collars”

Housing for “blue collars”

down town


8. Possible effects of “common wisdom” policy actions

These actions most likely will be some enduring form of emission taxes, road pricing for congestion in dense areas, maybe also severe standards for road vehicles. Reducing urban sprawl by normative action will remain un-effective, as in the past, given the land rent pressure.

Congestion charging will accelerate urban sprawl, and fiscally-and-standard-induced innovation will lead to low-emission vehicles.


9. Possible results

The final result can well be an American setting (more urban sprawl), but with reduced pollution from road traffic (low-emission vehicles), less congestion, and reduced urban rent. Economies of agglomeration will remain in terms of travel times, no longer in terms of physical proximity.

The argument of protecting agriculture ( a very polluting and low-employing activity) from urban sprawl will disappear together with the insane EU subsidies, and more land will be covered by forests and grasslands than by agriculture: a picture of hell?


Thanks for your attention!

Documents

Marco Ponti Urban density, the environment, and mobility, Venezia SIET September 20th, 2013 Marco Ponti – Politecnico of Milan Urban density, the environment,