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Traffic-related Air and Noise Pollution


2) Traffic-related Air and Noise Pollution

travel demand management strategies (e.g. carpooling, telecommuting) or the use of transit, all of which reduce the use of personal vehicles and overall air pollution emissions.

Finally, a shift in technology can reduce overall air quality emissions. For example, the use of electric or electric-hybrid vehicles greatly reduces tail pipe emissions from automobiles. It should be noted however that electric vehicles still have emissions associated with their production, the construction of roadway infrastructure, the wear and tear of the vehicle (e.g. tire scrapings) and the production of electricity (for example, coal power being more polluting than a hydro-electric production).

Case Studies

In the United States, Portland, Atlanta and Seattle have all explicitly attempted to deal with the nexus of land use, transportation and air quality. While the reasons for initiating the projects in the three cities are different, the tools suggested are very similar. However, the results for Portland and Atlanta are somewhat different, with Portland seeing much greater success. We discuss three recent prominent transportation related air quality policies below.


The impetus for LUTRAQ (Making the Land Use Transportation and Air Quality Connection) was the 1988 proposal of the Western Bypass, a highway west of Portland’s urban growth boundary. A preliminary study of the bypass showed that the demand for its construction was going to come from future low density, automobile development (Bartholomew, 1993). The aim of the LUTRAQ study was to determine the feasibility of a different growth scenario along with the promotion of alternative transportation modes attempting to address the effects

of land use character on the mode, type and amount of travel. In the analysis conducted by Cambridge Systematics, Calthorpe Associates and Parsons, Binckerhoff, Quade & Douglas three alternatives were considered (1,000 Friends of Oregon, 1997).

The first alternative was a “no build” scenario that left the city virtually unchanged with the exception of a light rail project that was already underway. The second option included the light rail line along with the proposed new bypass highway.

The final option was the LUTRAQ proposal adding transit oriented developments (TOD’s), higher densities, multiple rail lines, subsidizing transit and raising parking costs. The results of the analysis showed that LUTRAQ would drastically reduce the number of trips and vehicle miles traveled and roughly double the amount of transit trips for commute purposes. Further, the TOD’s were shown to be able to accommodate 65% of households and 78% of jobs forecasted.

In order to model the effects of the different land decisions on air quality, computer simulations of land use patterns and air quality were created for Portland using the DRAM/EMPAL land use model and improving on its capabilities to handle non-motorized travel modes since the model was traditionally used for vehicles (1,000 Friends of Oregon, 1996). The model conducted analysis on the impacts of the alternative on vehicle miles traveled and demonstrated that through a reduction in miles traveled due to land use changes and increased use of transit overall emissions would be significantly lowered. In 1997, Metro, Portland’s regional government voted to not build the highway structure. While LUTRAQ can be considered a success in terms of increasing mobility options and curbing sprawling land use patterns, it should come as no great surprises in ceplanning of this nature, (investing in light rail, promoting mixed-use developments, etc) started in Portland three decades earlier.


SMARTRAQ (Strategies for Metro Atlanta's Regional Transportation and Air Quality) was initiated in 1998 in response to Atlanta’s inability to conform to the requirements of the clean air act and was considered to be a non-attainment area, one which consistently exceeds the national ambient air quality standards.

The project added a health component to the transportation-land use-air quality framework developed in Portland (see above) relying on public health and epidemiological research demonstrating the link between physical activity and asthma. Further, they used a large panel survey consisting of 8,000 households to gain the opinions of residents on amenities and facilities that they would use such as mixed use developments and parks and their willingness to switch from the automobile to other travel modes.

In a summary report on the first phase of the program, Goldberg et al (2007) describe the benefits of high density, mixed-use and walkable communities. Their findings show that persons who live in the most walkable neighborhoods are more than twice as likely to moderately exercise (walk) for thirty minutes a day, after controlling for demographic characteristics. Moreover, this turns out to be the case regardless of whether people actually have a preference for walking or other physical activity. The nature of Atlanta’s road network comprised of strip commercial development and dead-end cul-de-sacs forces people to drive more and consequently use other modes of travel less than they otherwise would.

Despite SMARTRAQ’s efforts in the middle part of the last decade, Atlanta continued to be considered a non-attainment area for Ozone and Particulate Matter (EPA, 2006). Having been added to the group of “very large” metropolitan areas, the city ranks 4 th for annual hours of delay per person due to congestion(67hours) and wastes 70 million gallons of fuel at a cost of $1.7 billion annually(Schrank and Lomax,2005). The city is also rapidly sprawling. In the 1990’s the city almost

doubled its size from a north-south span of 65 miles to 110 miles with suburban growth being 100 times larger than that in the city(Bullard,2000).


LUTAQH (Land Use, Transportation, Air Quality & Health) is a study modeled on Atlanta’s SMARTRAQ model for King County, WA. One of the projects main goals is to raise awareness about this issue amongst the public government officials and developers. The study conducted Transportation panel and travel activity surveys and used parcel level data in assessing land use.

While many of the findings of the LUTAQH report (Frank et al., 2005) are consistent with those of SMARTRAQ’s, there are several items of note. First, similar to Whyte’s (1980) observation that “people like to sit where there are places to sit,” people tend to walk where there are places to walk—i.e. people walk more in places where there are sidewalks, retail shops, and a grid street design as demonstrated by the fact that persons living in walkable neighborhoods travel 26% fewer vehicle miles daily than those in sprawling area.

This is consistent with other studies that find that a grid pattern makes walking more desirable (Rajamani et al., 2003) and that most people residing within close proximity to transit station will walk or bicycle there unless they are impeded by a lack of sidewalks or busy arterials (Cervero, 2004). The LUTAQH report also notes that persons in walkable neighborhoods are considerably less likely to be obese and that air quality emissions (NOx,VOC’s) are much lower, perhaps due to the finding stating that for every 10% increase in street intersections there is a 0.5% decrease in vehicle miles traveled.

Air quality related health impacts

There are a wide variety of health impacts that can arise due to air pollution.

The following discussion summarizes the impacts from the most prevalent transport related pollutants.

Particulate matter (PM 2.5 and PM10) exposure causes increases in respiratory mortality, hospital respiratory admissions and reduced activity days. Particulate matter is especially troubling because of its prevalence near roadways and relatively large size (about one fifth the width of a human hair (See the left image of Figure 2). There are generally three types of particulate matter that receive attention, which vary by their width 10, 2.5 and 1 micrometer (mm: one millionth of a meter). The smaller the size of the particulate, the further it can travel within the human lung and the more damage that it can cause. While the larger particulates might stay within the nasal cavity or cause a person to sneeze, the smaller particles will travel deep within the lungs to the blood vessels and alveoli (See the right image of Figure 2).

Figure 2 Particulate Matter (PM) and Respiratory Health

Prolonged exposure to particulates can lead to exacerbation of asthma related symptoms, depressed lung function, and increases of bronchitis and lung cancer.

In Vancouver, British Columbia, air pollution related deaths have been shown to be higher than most other causes, similar to alcohol related deaths and significantly lower than only smoking related deaths (Brauer, 2000) (See Table 3).

Table 3 Number of Death according to Causes

Cause Death/Year

Accidental falls 167

Motor vehicle accidents 169


Suicide 239

Drug 311

Air Pollution (estimate) 0 to 600

Alcohol 869

Smoking 4,446

Ultrafine Particulate Matter

Although similar to the larger particulates, ultrafine particulate matter, those that are nano-sized, (less than 100nm) have their own implications for human health. Inhalation of ultrafine particulates has been shown to increase cardiovascular morbidity in people with chronic heart conditions (Morawska et al 2004). Further, they have been shown to cause a variety of cardiovascular symptoms such as increased blood pressure (Delfino et al, 2005). Most troubling of all, in reviewing multiple studies on the impacts of ultrafine particulates, Pope and Dockery (2006) and Brook et al (2010) conclude that prolonged exposure to these pollutants reduces life expectancy.

Other pollutants

Some of the other prominent pollutants include Lead, Ozone, Carbon Monoxide, Sulfur dioxide and Nitrogen Dioxide. Lead exposure can lead to impaired blood formation and hurt fetal development, especially brain damage. However, because

lead has not been included in fuels since the 1970’s it is of minimal concern.

Carbon Monoxide leads to a lower tolerance for exercise and aggravation of angina.

Nitrogen Dioxide’s most prevalent impact is aggravation of respiratory disease.

Ground level Ozone reduces pulmonary function, causes eye irritation and is harmful to vegetation. Sulfur dioxide causes wheezing, shortness of breath and chest tightness. While all of these pollutants have different impacts, in general they all cause respiratory problems and prevent or hampers people’s ability to be physically active.

Diesel Fuel and Freight

Freight vehicles, especially larger long-haul trucks (as opposed to smaller urban delivery vehicles) predominantly rely on diesel fuel and are responsible for a large share of the overall particulate matter emissions related to roadway vehicles.

Emissions from these larger vehicles are of particular concern to bicyclists and pedestrians in areas where industry overlaps with other land uses or in locations where complete streets policies or circumstance necessitate that these vehicles share the right of way.

From the vehicle owner’s perspective, the diesel engine is desirable because it lasts far longer than the alternatives. Newer trucks are generally cleaner than their older counterparts with improved technology specifically aimed at reducing air quality emissions. For the older vehicles, retrofits to the truck components can save fuel, which reduces the operator’s cost and lower overall emissions.

An example of retrofit technology is the relatively inexpensive ($1,000USD) oxidation catalysts. Switching to these catalysts can reduce particulate matter emissions by 30% and volatile organic compounds by roughly 50%. The oxidation catalysts are in prevalent use across the United States.

Similarly, diesel filter traps can have a large benefit in reducing emissions though

are only marginally popular in the United States, perhaps due to their unit cost of roughly $5,000. Nonetheless, the filter traps are in widespread use across Europe and can reduce both particulate matter and volatile organic compound emissions by roughly 90%.

In additions to improvements to a truck’s engine, improvements to the aerodynamics of the vehicle can make it more efficient (See Figure 3). The aerodynamics improvements can save roughly a quarter of the fuel or 5,000 miles of travel annually with a reduction of a quarter of the particulate matter and nitrogen oxides and a savings of 50 metric tons of carbon dioxide per truck per year.

Figure 3 Aerodynamic truck improvements (source EPA)

Put another way, upgrading 30,000 older trucks could save 150 million gallons of fuel, 625 tons of diesel particulate matter, 22,500 tons of nitrogen oxides, 1 ½ million tons of carbon dioxide and a saving of nearly a half billion dollars on fuel.

Other Fuels

In part because of emissions related to using traditional fossil fuels, car manufacturers have been turning their attention to alternative fuels. In terms

of emissions, electric vehicles are by far the most promising, having the potential for a zero tail pipe emission vehicle. While these vehicles improve the near-road environment for pedestrian and bicyclists, some consideration should be given to the manufacture of the fuel, with coal burning plants being far more polluting than hydro-electric plants. At present, the cost of electric and electric-hybrid vehicles is still relatively high, though education campaign about fuel costs over the life of the vehicle may make these vehicles more popular than they are at present.

Ethanol has also been considered an improvement on traditional fossil fuels because it comes from a renewable resource (plant matter) and produces very low emissions of ozone forming hydrocarbon toxics. Nonetheless, Ethanol is still relatively expensive and competes with food production.

Finally, natural gas shares the same benefits of ethanol in very low hydrocarbon emissions and is an excellent fleet fuel used by large institutions. However, at present, refueling can be a problem due to a lack of stations and the fuel economy is not as good as traditional fuels.

Bicycling and air pollution

The negative effects of air pollution on human health have been well documented.

For recent reviews of the topic, please see Bae et al (2007) and Dannenberg (2003). This review focuses on the most recent (2010 to 2012) academic literature that specifically considers the impacts of mobile source air pollution related to bicycling. Attention is also given to novel approaches for measuring pollution in relation to bicycle use.

Although the negative effects of mobile source pollution are well understood, the micro-scale (neighborhood and street-level) impacts are far less clear. Bassok et al (2010) used mobile monitoring to demonstrate that localized emission levels

significantly differed from ambient measures. There are a number of recent studies that demonstrate the scale of the difference for bicyclists, clearly demonstrating that while ambient pollutant levels may be within an acceptable range, bicyclists have a far greater risk for exposure.

Huang et al (2012) employed a mobile monitoring method and concluded that stationary monitors should not be used to assess pollution levels for bicyclists, particularly because bicyclists have higher exposure to particulate matter than do other modes. Fajardo and Rojas (2012) employed a similar method along heavily trafficked facilities and found that bicyclists are exposed to particulate matter at between six and 18 percent higher levels than other persons in the same location depending on the level of effort expanded by the bicyclist. Hong and Bae (2012) also utilized a mobile monitoring approach and similarly concluded that bicyclists are at a higher risk for exposure in locations with large commercial vehicles and transport related land uses.

While multiple studies have shown bicyclists to bear higher concentrations of pollutants, there is now evidence that the overall concentrations are less important than ventricular exposure. Panis et al (2010) demonstrate that exposure for a bicyclist is 4.3 times higher than it is for motorists. Further, Jacobs et al (2010) found that bicycling in traffic as compared to a clean room led to an increase of inflammatory blood cells. While these studies stop short of discussing the health implications, it is clear that it is both necessary to measure bicyclist’s exposure and those bicyclists are far more susceptible to pollution than other users of the road system.

Nonetheless, caution should be exercised in generalizing all of these results and further location-specific analysis should be conducted ahead of planning changes to existing or new bicycle facilities. Indeed, Knibbs et al (2011) reviewed nearly 50 different exposure studies across multiple modes and concluded that although

the general trends previously discussed appear to be consistent, factors such as fuel type, meteorology or route choice have a profound impact on exposure and that careful attention should be given to individual cases. Further, Moniek et al (2011) conducted mobile monitoring of pollution for commuters and found that bicyclists had a lower count of particulate matter particles. This finding could perhaps be explained by the utilization of separated bicycle facilities, again highlighting the need to conducted local analysis.

In addition to concerns related to negative impacts to bicyclist’s health related to mobile source pollution, there are also notable benefits. For example, a reduction in short automobile trips, which improves ambient air quality, can stimulate a shift to bicycle use that also has a positive benefit of reducing obesity (Grabow et al, 2012). Indeed, Rabl and Nazelle (2012) demonstrated that while mode shifts to bicycling from driving have some benefit to ambient air quality, the largest benefit is to the individual bicyclists in terms of health improvements.

Nonetheless, for these health benefits to be fully realized, it is desirable for bicyclists to engage in travel on less polluted facilities, again highlighting the need to understand and mitigate pollution at the micro-scale.

Studies concerned with morbidity rates come to similar conclusions. De Hartog et al (2011) note that switching to active transportation modes increases a person’s life by three to 14 months, while the negative effects of riding a bicycle and being exposed to pollutants reduces life by between one and 40 days. Rojas-Rueda et al (2011) compared mortality of bicyclists versus other road uses and concluded that the negative air quality impacts cause annual increase of bicyclist deaths of .13 but that the associated health benefits from active living create a situation where nearly 12.5 deaths are avoided annually. A further study by Lindsay et al (2011) modeled the implication of mode shift for short trips away from automobiles to bicycles and found that annual deaths would be reduced by over 100 people

due to physical activity with an additional six deaths avoided due to improved air quality from lower greenhouse gas emissions (the study does note a small increase in fatalities due to bicycle incidents). While the difference is staggering, it suggests that improvements in separated bicycle facilities or appropriate planning for the location of facilities would allow jurisdictions to gain the benefits from physical activity while minimizing the air pollution related risks of bicycling in heavy traffic.

Regardless of the actual impacts of air pollution to bicyclists, the perception of a polluted facility or corridor is a significant deterrent for bicyclists. Winters et al (2011) conducted a large survey of bicyclists and found that across all skill levels, facilities that were perceived to be less polluted and less noisy were more desirable and among the top motivations for bicycling. This finding suggests that in addition to improving and protecting health, designing facilities away from polluted, high-traffic roadways will incentivize mode shift among users.

Facility design itself has been shown to increase bicycle use, where most novice cyclists prefer separated facilities. In terms of air quality, it is now becoming apparent that separated facilities and careful facility design can lower a bicyclist’s exposure. This relationship is keenly demonstrated by Kendrick et al (2011) who show that exposure to particulate matter is significantly lower for a cycle track than for a bicycle lane. Similarly, Strak et al (2010) demonstrate that high traffic facilities have nearly 60% more particulate matter than low-traffic roadways.

As more epidemiological studies consider the impacts of traffic related air pollution on cyclists a few generalizations can be made. First, air quality is localized and careful monitoring should be done in a local context to understand bicycling conditions. Second, ceteris paribus, bicyclists are exposed to significantly higher levels of pollution than other uses of the roadway, which could be mitigated by separated facilities that would also promote bicycling use.

Pedestrians and Air Pollution

The health impacts to pedestrians related to air pollution emissions is similar to that of bicyclists. However, in general, pedestrians interact with the built environment on sidewalks as opposed to bicycles that share the roadway with other vehicles. There are a few notable academic research studies that specifically consider air quality and the pedestrian environment. That body of research is briefly presented in this section.

The most significant finding from personal and mobile monitoring is that air pollution levels vary widely at the micro-scale and in different environments.

Lonati et al (2011) carried out measurements of particulate matter concentrations in Milan, Italy and found that pollutant levels varied across the routes travelled and particularly varied between outdoor areas and those of the indoor subway stations.

The built environment has a clear effect on pollution levels. In built out areas with tall building on both sides of the street there is an “urban canyon” effect that traps in the pollutants. Buonanno et al (2011) examined this effect in an Italian town and found the effect pronounced in the pedestrian environment.

They further found that congested traffic led to finer particulate emissions as compared to free flowing traffic—i.e. the pollution conditions for pedestrians worsen along with traffic congestion. Not surprisingly, when pedestrians are separated from vehicle traffic, pollutant levels decrease as shown by King et al (2009) who undertook a combined noise and air quality examination of a new boardwalk in Dublin, Ireland.

Beyond the urban canyon effect, the built environment, in terms of walkability may present an environmental justice challenge. Marshall et al (2009) examined walkability and air pollution in Vancouver, BC and found that, ceteris paribus, in dense urban settings with good walkability, nitrogen oxide levels were generally

high and ozone levels were low as compared to less urban areas. Along with this finding, Marshall et al note that wealthier areas had lower pollution levels than poorer parts of the city. This suggests that special attention should be given to traditionally underserved populations.

For pedestrians, the interaction with heavy freight vehicles can also cause concern in terms of pollution related to diesel fuels. Olajire et al (2011) conducted mobile measurements of a number of pollutants for 72 days on roadways in Nigeria and found that pollutants rise sharply with the number of heavy vehicles. This result is not surprising, but it confirms the finding of other studies and does so within the context of mobile monitoring of the pedestrian environment.

The negative impact from diesel fuel to the pedestrian environment is not limited to freight vehicles. Gouge et al (2010) conducted an analysis of emissions of bus stops along a bus rapid transit route and found emissions to be between one and a half and three times higher than along the route in general. Gouge et al’s findings suggest that special attention should be given to bus stations, but also again highlight the variability of air quality at the micro-scale.

(2) Traffic-related Noise Pollution

The literature was selected from recent peer reviewed articles which had different research methodologies, and/or covered different regions in the world. However, there is an important common challenge: They had difficulty measuring the impact of noise on human health because it usually affects people for a long time rather than for a moment, which caused confounding factors. Namely, it was difficult to assess the exact extent of the impact of noise on health. Within this context, we investigate literature based on four different categories: (1) meta-analysis, (2) personal monitors, (3) survey data, and (4) Korean case studies.

Literature based on meta-analysis

Kempen et al. (2002) investigated the relationship between community and occupational noise exposure and blood pressure and/or ischemic heart disease via the meta-analysis based on 43 epidemiological studies published from 1970 to 1999. While the paper reports that every 5dB increases the risk of hypertension by 1.14-1.26 in air traffic noise, the results indicate that traffic noise exposure can contribute to myocardial infarction (aka. heart attack) and ischemic heart disease. The latter relationship was inconclusive though, because it had complexity with regard to noise and the health effects mentioned above. To be specific, the research, largely occurred in the Netherlands, Germany and the U.K., had several limitations in exposure characterization, blood pressure measurement and/or definition of hypertension, adjustment for important confounders, and the occurrence of publication bias.

Figure 4 Conceptual Model of the Interaction of Noise with Humans and the Effects on Health

Source: Kempen et al., 2002, p.308