Street-network Sprawl in Silay, Philippines

What is Street-network sprawl?

Street-network Sprawl is a way to measure urban sprawl, worldwide, through the connectedness of the streets. Less sprawl means more connected, more walkable streets. Well-connected streets – like New York City’s grid – are more walkable and can be served by public transit.

The street network is permanent, and its connectivity affects the livability and environmental footprint of cities for decades and centuries to come. In places with more connected streets, residents drive less and walk more. A well-connected street network is associated with better outcomes for health, the environment, sustainable consumption, social integration, and equity.

We can quantify how connected street networks are with the Street Network Disconnectedness Index (SNDi).

SNDi -- our measure of street-network sprawl (disconnectedness)

The SNDi is a comprehensive measurement of “sprawl”. It captures:

A higher SNDi means less-connected streets – i.e., more sprawl. For the 10137 cities in our dataset, the average SNDi is 2.25, with half of the cities' SNDis falling between 1.08 and 3.25.

More information on the sprawl index can be found in these research papers:

To see the state of street-network sprawl across the globe, visit the sprawlmap.

Silay: city in Negros Occidental, Philippines

What exactly constitutes the spatial extent of the city? For these aggregations, we used the Global Human Settlement Layer Urban Center Database (GHS-UCDB) to define the boundaries of the city. These cities -- or urban centers -- cover areas that are densely populated and built-up, and so may extend beyond the spatial borders of these cities that we may be familiar with. The GHS area is shaded in blue.

View Silay, Philippines on the sprawlmap

Most recent snapshot: Taking into account the entire (i.e. aggregate) street network in Silay as of 2014, the overall level of street-network sprawl is 3.24, which is in the 40th to 60th percentile of disconnectedness.

Trends in street network construction: The SNDis of street construction for the respective time periods are 2.75, 3.32, 6.81 and 3.35. Street construction in Silay increased in disconnectivity initially but has since improved. The streets constructed in 1991-2000 were the most disconnected.

Quantity of street network construction: The street network in Silay spans a total of 92 kilometers. The period with the greatest volume of street construction was 1976-1990. These roads have an SNDi of 3.32, which is highly disconnected.

Effect on the aggregate network: New construction in each period adds to the total stock of streets, but does not change streets that have already been built. Therefore, it has a limited effect on the street network as a whole. The SNDis of the aggregate street network in the respective time periods are 2.75, 3.0, 3.21 and 3.24. Overall, the SNDi of the aggregate street network has risen: the street network in Silay has become more disconnected. This increase has slowed: between 1975 and 1976-1990, SNDi rose by 0.25 points, but between 1991-2000 and 2001-2014, it rose by just 0.03.

Silay and Negros Occidental do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Silay peaked in 1991-2000, while the SNDi of street constructions in Negros Occidental rose steadily.

How do development practices in Silay fare in comparison to others in Negros Occidental? Most recently in 2001-2014, street construction in Silay was the 3rd-most disconnected out of the 4 cities in Negros Occidental. Its position in the ranks since 1975 has fallen; relative to other cities in Negros Occidental, street construction in Silay has become more connected. Silay ranked 2nd in 1975, 2nd in 1976-1990, 1st in 1991-2000 and 3rd in 2001-2014.

Silay and Philippines do not follow the same trend in the disconnectivity of their street network constructions. The SNDi in Silay peaked in 1991-2000, while the SNDi of street constructions in Philippines rose steadily.

How do development practices in Silay fare in comparison to others in Philippines? Most recently in 2001-2014, street construction in Silay was the 72nd-most disconnected out of the 89 cities in Philippines. Its position in the ranks since 1975 has fallen; relative to other cities in Philippines, street construction in Silay has become more connected. Silay ranked 47th in 1975, 65th in 1976-1990, 13th in 1991-2000 and 72nd in 2001-2014.

Silay and Negros Occidental follow the same trend in the disconnectivity of their aggregate street networks. The SNDi for both of these rose steadily.

To date, Silay is the 2nd-most disconnected out of the 4 cities in Negros Occidental. Its position in the ranks since 1975 has not changed. Silay ranked 2nd in 1975, 2nd in 1976-1990, 2nd in 1991-2000 and 2nd in 2001-2014.

Silay and Philippines follow the same trend in the disconnectivity of their aggregate street networks. The SNDi for both of these rose steadily.

To date, Silay is the 73rd-most disconnected out of the 89 cities in Philippines. Its position in the ranks since 1975 has fallen; relative to other cities in Philippines, the street network in Silay has become more connected. Silay ranked 47th in 1975, 69th in 1976-1990, 69th in 1991-2000 and 73rd in 2001-2014.

As of 2015, Silay had a built-up area of 0.8 square kilometers, and a population of 60133 people.

These are some other cities with approximately the same population: