Connected streets promote urban resilience聽

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Connected streets promote urban resilience聽

The Issue

The connectivity of local streets shapes travel choices for residents and the long-term resilience of cities. In neighbourhoods with connected streets鈥攃haracterized by a grid or similar pattern with direct walking routes and few dead ends鈥攔esidents walk more and own fewer cars. Where streets are disconnected鈥攆or example, in hillside canyons or gated communities鈥攖he private car is typically the only option. And once laid down, street patterns rarely change, even after fires, wartime bombing, and earthquakes.

We quantified the connectivity of streets for the entire world using a composite indicator鈥攖he Street-Network Disconnected index (SNDi). Here, we focus on some of the trends and the implications for urban resilience, especially for wildfire risk in California.

Key Research Findings

Neighborhoods with the highest wildfire risk have the least connected streets. Previous research shows that connected streets can facilitate rapid evacuations after disasters such as earthquakes and floods as well as wildfires. The existence of multiple ways out reduces the likelihood of traffic congestion at chokepoints, and gives residents and first responders alternative routes if a road is blocked. But in California, streets are less connected in the neighbourhoods that are most at risk 鈥� i.e., those that have been subject to wildfire evacuation orders or warnings, or lie within historical wildfire perimeters (Figure 1, Figure 2).

The connectivity of streets in new developments has improved in the US and California, but is still low by global standards. Since 2005, new streets in the US have been built with fewer deadends and less circuitous routes. But their connectivity still lags that of older (pre-1975) US developments, and compares poorly to countries in South America, Europe, and East Asia (Figure 3).

Japanese cities have some of the most connected streets, even in new suburbs. Rather than a grid, cities such as Tokyo and Osaka are typified by a more organic mesh of narrow streets with 3-way intersections.

Planners can set connectivity standards for streets in new developments. In the US, states such as Oregon and cities such as Fort Worth (TX), Raleigh (NC), and Fort Collins (CO) are among those with policies or subdivision regulations that specify minimum connectivity levels, require direct pedestrian routes, or discourage or prohibit dead ends.

As well as shaping the street patterns of new developments, planners can, to some extent, retrofit existing neighborhoods to improve connectivity. Pedestrian cut-throughs can link adjacent cul-de-sacs or connect to neighborhood greenways, as in many Danish cities and some California cities such as Davis and Irvine. Pathways can be provided along flood channels or other infrastructure, linking homes with shops, schools, and services. Where freeways are the barrier, cities can build pedestrian bridges and upgrade sidewalks on existing streets that cross the freeway.