Intersection density linked to a reduction in obesity, high blood pressure, diabetes and heart disease
Literature associated to the built environment to health outcomes is vast, it glosses over the role that specific street network characteristics play.
Researchers from the University of Colorado – Denver and the University of Connecticut tested the link between community design and public health.
According to Dr. Wesley Marshall, PhD, PE, assistant professor of civil engineering at CU- Denver and co-author of study "Previously we had found that people drive less and walk more in more compact cities with more intersections per square mile,” "Now we've been able to link these city design qualities to better health."
The researchers asked themselves the following question; what is the influence of the three fundamental measures of street networks on obesity, diabetes, high blood pressure, heart disease, and asthma?
In order to answer this question the team examined 24 California cities exhibiting a range a street network typologies using health data from the California Health Interview Survey for the years 2003, 2005, 2007 and 2009, sampling between 42,000 and 51,000 adults.
The researchers had controlled for the food environment, land uses, commuting time, socioeconomic status, and street design.
The results suggest that more compact and connected street networks with fewer lanes on the major roads are correlated with reduced rates of obesity, diabetes, high blood pressure, and heart disease among residents. The more intersections, the lower the disease rates.
The team also found a correlation between wider streets with more lanes and increased obesity and diabetes rates. The researchers noted the reason for this was that wider streets may be indicative of an inferior pedestrian environment. The presence of a 'big box' store also tends to be indicative of poor walkability in a neighborhood and was associated with a 13.7 % rise in obesity rates and a 24.9 % increase in diabetes rates.
The study also looked at the `food environment' of cities. Cities with more fast food restaurants were linked with higher diabetes rates while additional convenience-type stores across a city correlated with higher rates of obesity and diabetes.
Overall, more compact street networks with smaller major roads are correlated with better health.
Dr. Marshall noted that while Denver falls on the more compact side of the city spectrum, it also has far too many major streets with wide, multiple lanes that were associated with increased obesity and diabetes rates.
According to Dr. Marshall, "Over the course of the 20th century, we did a great job of engineering utilitarian active transportation out of our daily lives.”
Marshall said it may still be uncommon to choose a place to live based on health outcomes but this research indicates that it might be worth considering.
While it is possible to lead an active, healthy lifestyle in most any type of neighborhood," he said. "Our findings suggest that people living in more compact cities do tend to have better health outcomes."
Dr. Norman Garrick, PhD, associate professor of engineering at the University of Connecticut, and co-author of study commented We built these dense, connected street networks for thousands of years but only over the last century or so did we switch to designing sparse, tree-like networks with cars in mind.”
Dr. Garrick mentions that in their earlier study they had found that these more compact cities also had much lower levels of traffic fatalities.
In closing he states "Taken together these findings suggest a need to radically re-think how we design and build the streets and street networks that form the backbone of our cities, towns and villages.” "This research is one more in a long line that demonstrates the myriad advantages of fostering walkable places."
This study is published in the Journal of Transport & Health