Universal scores for accessibility and inequalities in urban areas

Indaco Biazzo
Politecnico di Torino
SmartData@PoliTO - DISAT

personal page -- http://indacobiazzo.me/

CityChrone -- www.citychrone.org

Today:

Introduction:

Motivation and context.

Scientific results:

Universal scores for accessibility and inequalities in urban areas.

CityChrone Platform:

an interactive platform for urban accessibility studies and planning.

Motivations

High entrance barriers

You need a Ph.D. in the specific domain to do research. But sometimes even to understand the results.

Overspecialization in Science

Very difficult to cross the branches of science.

Slow learning curve

Very difficult to perform self-education path

images:[ Branch Tree Drawing Clip art - branches clipart @kisspng ,]

Components

"Simplicity is the ultimate sophistication"

Data visualization

Interactive visualizations of results.

Gamification

Involve general audience to partecipate.

images:[ Jegi - flickr ]

Motivations 2

I was born in Rome

I had a very difficult childhood

Rome public transport are "not so good".
Ok. But how much compared to the other cities?

Where is the better served [by public transport] place in the city?
And in the world?

Urban Accessibility measures

Huge scientific literature

The first definition of accessiblity in urban context is done more than 50 years ago

Many different definitions of accessibility

But no attemp to compute it at large scale.

A science of city needs quantitative measurement.

We want easy to understand, easy to compute and meaningful quantities to measure public transport efficiency.

And we define and measure them.

Boundaries and Tessellation.

It is possible to compute isochrones

First step towards an accessibility measure:

The larger isochrones are, the faster you move.

Velocity Score

Consider the Area of the Isochrone a time \(t\) computed in \(P\): \begin{equation} r(t,P) = \sqrt{\frac{A(t, P)}{\pi}} \end{equation}

dividing by time, we obtain a quantity with the dimension of a velocity:

\begin{equation} v(t,P) = \frac{r(t,P)}{t} \end{equation} Integrating over time: \begin{equation} v_{score}(P) = \frac{\int_0^{\infty} v(t, P) f(t) dt}{\int_0^{\infty} f(t) dt}, \end{equation} \(f(t)^1\) is the daily time budget distribution for public transport.

The Velocity Score can be consider as the average velocity of a daily typical trip taking a random direction from \(P\).

\(^1\) Robert Kölbl, Dirk Helbing. Energy laws in human travel behaviour. New Journal of Physics 5, 48 IOP Publishing, 2003.

Velocity Score

Average velocity taking a random direction

Paris Rome

interactive maps and more cities:

citychrone.org

Sociality Score

Consider the populations inside the Isochrone a time \(t\) computed in \(P\): \begin{equation} s(t,P) = \sum_{i \mid t_i(P) < t} p(h_i), \end{equation}

we sum over all the hexagons with time \(t_i\) less than \(t\) and \(p(h_i)\) is the population within \(h_i\).

\begin{equation} s(P) = \frac{\int_0^{\infty} s(t,P)f(t)dt}{\int_0^{\infty} f(t) dt}, \end{equation}

\(f(t)^1\) is the daily time budget distribution for public transport.

The Sociality Score quantifies how many citizens it is possible to reach with a daily typical trip starting from \(P\).

\(^1\) Robert Kölbl, Dirk Helbing. Energy laws in human travel behaviour. New Journal of Physics 5, 48 IOP Publishing, 2003.

Sociality Score

Number of people is possible to reach in a typical day trip starting from a point.

Paris Rome

interactive maps and more cities:

citychrone.org

City Rankings

City Velocity

Velocity Score per person

City Sociality

Sociality Score per person

Cohesion

City Sociality divided by total population

Distributions

Values distribution

Area distributions - Population distributions

Inequality distribution of accessibilities

Exponential decay from the center of the city.

fitting function: \(f(t) = e^{-t/\tau} + \sigma_0 \)

Exponential decay from the center of the city.

fitting function: \(f(t) = e^{-t/\tau} + \sigma_0 \)

Why these patterns are observed in all cities?
Are these inequalities unavoidable?

Can be modified or optimized?
In which way?

CityChrone
Interactive platform

Citizen Science [DataViz & Gamification]

SETI@home [1999]: analyze radio signals, searching for signs of extraterrestrial intelligence. People can partecipate using their PC, donating their computational resources.

foldit [2008]: fold the structures of selected proteins as perfectly as possible, using tools provided in the game. Nature paper with credits more than 57000 authors.

Quantum Moves [2012]: simulations of logical operations in a quantum computer. Played over 8 million times by more than 200,000 players worldwide. The 200 000 players were all beaten by the stochastic optimization method. :(

Algorithms: routing in urban context

Walking routing algortimh:
OSRM

New class of public transport routing algorithms:
CSA [2013], RAPTOR [2011]

This new class of algoritms are easy to implements and fast, but they have some crucial limitations in urban context.

They needs to be closure by transitiveness in the walking path.

We modified the CSA and the RAPTOR algorithm in order to use it in urban context.

CityChrone
Interactive platform

Now I know how much Rome public transports suck

What we have to do to reach Paris?

What are the best interventions given a budget?

Let's Play!

CityChrone
Interactive platform for exploring new scenario

Budget: 5 Bilion €

Name Scenario: Gram Author: Pietro

After 1 year

Name Scenario: rer + circle Author: mat

Useful Links

Interactive platform:

citychrone.org

Open Source and Open Data:

project.citychrone.org

Article:

theoretical results [arxiv]

Today presentation:

indacobiazzo.me

Sponsor:

SmartData@PoliTO

Collaborators: