Onitsha in context: Street-network sprawl trends

The chart above shows SNDi trends for new street additions (left panel) and the entire network (right panel), with Onitsha plotted against Anambra and Nigeria. The SNDi of new construction in Onitsha peaked in 1976-1990, compared to Anambra which followed a zig-zag trend with an overall increase and Nigeria which followed a zig-zag trend with an overall increase. Most recently, Onitsha's incremental SNDi fell from 4.54 to 4.25 between 1991-2005 and 2006-2020. In terms of the aggregate network, Onitsha ranked 4th out of 4 cities in Anambra and 316th out of 422 in Nigeria as of 2020.

Rankings go from most connected to most disconnected — rank 1 is the most connected.

What about similarly populated cities?

• Guadalajara, México
• Faisalabad, Pakistan
• Harbin, China
• Belo Horizonte, Brazil
• Islamabad, Pakistan
• Wenzhou, China

While Guadalajara and Belo Horizonte both built increasingly disconnected streets over time, Onitsha built increasingly disconnected streets from 1975 through 1976-1990, then improved in new street additions. For the full street network, though, all three cities follow the same trend. Onitsha and Guadalajara have been converging in their street-network character since 1975.