Written by: Sara Dennis
This article is the fifth in a series we are posting about how a city's infrastructure impacts its residents. In this article we investigate how infrastructure can impact air quality, and in turn impact our health.
Roads in the US are getting more crowded and congested, and the total vehicle miles traveled (VMT) hit a record high in 2016 with 3.2 trillion miles. Congestion refers to periods when the volume of traffic exceeds the road’s capacity, think about a traffic jam where cars sit idling. All over the US, congestion is getting worse, especially in urban areas. One study found that from 1980 to 2003 the total VMT increased by 111% in urban areas, while urban lane-miles only increased by 51%, which created a net effect of heavier traffic congestion.
The emphasis on congestion is important because when cars speed-up, slow down, start and stop, more emissions are released than when a car drives normally. For example, when comparing a road with “cruise conditions” (an average speed of 38-44 mph) vs. a road with congested conditions (an average speed of 13 mph), we see an increase of four times the amount carbon monoxide emissions, three times the amount of hydrocarbon emissions and twice the amount of nitrous oxides emissions. The amount of emission concentrations in an area can have a significant impact on health. People who live near busy freeways are more likely to suffer from asthma, lung cancer, pre-term births and heart attacks.
One study also looked at the impact of a policy change in Pennsylvania and New Jersey, which introduced the EZPass®, an electronic toll collection system that allows users to go through a toll without having to stop and pay at a tollbooth. This greatly helped reduce delays at toll plazas, and pollution caused by idling, accelerating and decelerating. Furthermore, EZPass® adoption also has spillover effects for automobiles by thinning out the lines and decreasing overall wait periods to pay at the tollbooths. Overall the study found that the reduction in congestion reduced the incidence of premature births by 6.4% and low birth weights by 8.6% among mothers within 2 kilometers of a toll plaza.
The study concluded that “Policies intended to curb congestion can have significant health benefits for local populations in addition to the more often cited benefits of reducing travel costs” (Currie and Walker, 86). Other policies that may help contribute to reducing traffic congestion and improving air quality in urban areas include:
Promoting the use of public and alternative transportation (to decrease automobile use)
Planting roadside vegetation barriers to help improve air quality near roadways
Offering incentives for carpooling to work or commuting during outside of rush-hour, and similarly, demand-based toll pricing (the 66 Express Lanes in Virginia and DC are experimenting with this – offering a free toll to those carpooling, and charging single-occupancy vehicles more depending on the amount of traffic)
Discouraging new development close to congested roadways
It’s important to consider economic impacts as well as health impacts when planning new infrastructure and developments.
Check out the rest of our series about how a city's infrastructure impacts its residents: Transportation Infrastructure, Walkable Infrastructure in Cities, Growth and Infrastructure in a Growing City, and Building Accessible Infrastructure for Everyone.
1. Baldauf, R. "Recommendations for Constructing Roadside Vegetation Barriers to Improve Near-Road Air Quality." National Risk Management Laboratory Office of Research and Development, Air Pollution Prevention and Control Division: Washington, DC, USA (2016).
2. Currie, Janet, and Reed Walker. "Traffic congestion and infant health: Evidence from E-ZPass." American Economic Journal: Applied Economics 3.1 (2011): 65-90.
3. Eherts, Faith. “Air Quality, the Environment and Infrastructure.” Local Weather from AccuWeather.com - Superior Accuracy™, AccuWeather, 18 Aug. 2017.
4. Zhang, Kai, and Stuart Batterman. "Air pollution and health risks due to vehicle traffic." Science of the total Environment 450 (2013): 307-316.