Center for Earth Systems Engineering and Management

This report is the consolidated work of an interdisciplinary course project in CEE494/598, CON598, and SOS598, Urban Infrastructure Anatomy and Sustainable Development. In Fall 2012, the course at Arizona State University used sustainability research frameworks and life-cycle assessment methods to evaluate the comprehensive benefits and costs when transit-oriented development is infilled along the proposed light rail transit line expansion. In each case, and in every variation of possible future scenarios, there were distinct life-cycle benefits from both developing in more dense urban structures and reducing automobile travel in the process.

Results from the report are superseded by our publication in Environmental Science and Technology.

Study Background: Researchers at ASU have determined that significant energy and environmental benefits are possible in the Phoenix metro area over the next 60 years from transit-oriented development along the current Valley Metro light rail line. The team evaluated infill densification outcomes when vacant lots and some dedicated surface parking lots are repurposed for residential development. Life cycle building (construction, use, and energy production) and transportation (manufacturing, operation, and energy production) changes were included and energy use and greenhouse gas emissions were evaluated in addition to the potential for respiratory impacts and smog formation. All light rail infill scenarios are compared against new single family home construction in outlying areas.

Overview of Results: In the most conservative scenario, the Phoenix area can place 2,200 homes near light rail and achieve 9-15% reductions in energy use and emissions. By allowing multi-family apartments to fill vacant lots, 12,000 new dwelling units can be infilled achieving a 28-42% reduction. When surface lots are developed in addition to vacant lots then multi-family apartment buildings around light rail can deliver 30-46% energy and environmental reductions. These reductions occur even after new trains are put into operation to meet the increased demand.

Already the leading cause of weather-related deaths in the United States, extreme heat events (EHEs) are expected to occur with greater frequency, duration and intensity over the next century. However, not all populations are affected equally. Risk factors for heat mortality—including age, race, income level, and infrastructure characteristics—often vary by geospatial location. While traditional epidemiological studies sometimes account for social risk factors, they rarely account for intra-urban variability in meteorological characteristics, or for the interaction between social and meteorological risks.

This study aims to develop estimates of EHEs at an intra-urban scale for two major metropolitan areas in the Southwest: Maricopa County (Arizona) and Los Angeles County (California). EHEs are identified at a 1/8-degree (12 km) spatial resolution using an algorithm that detects prolonged periods of abnormally high temperatures. Downscaled temperature projections from three general circulation models (GCMs) are analyzed under three relative concentration pathway (RCP) scenarios. Over the next century, EHEs are found to increase by 340-1800% in Maricopa County, and by 150-840% in Los Angeles County. Frequency of future EHEs is primarily driven by greenhouse gas concentrations, with the greatest number of EHEs occurring under the RCP 8.5 scenario. Intra-urban variation in EHEs is also found to be significant. Within Maricopa County, “high risk” regions exhibit 4.5 times the number of EHE days compared to “low risk” regions; within Los Angeles County, this ratio is 15 to 1.

The project website can be accessed here. 

Climatic changes have the potential to impact electricity generation in the U.S. Southwest and methods are needed for estimating how cities will be impacted. This study builds an electricity vulnerability risk index for two Southwest cities (Phoenix and Los Angeles) based on climate-related changes in electricity generation capacity. Planning reserve margins (PRM) are used to estimate the potential for blackouts and brownouts under future climate scenarios. Reductions in PRM occur in both cities in 2016 with the most significant reductions occurring in regions relying more heavily on hydropower.

Mitigation of urban heat islands has become a goal for research and policy as urban environmental heat is a rapidly growing concern. Urban regions such as Phoenix, AZ are facing projected warming as urban populations grow and global climates warm (McCarthy et al. 2010), and severe urban heat can even lead to human mortality and morbidity (Berko et al. 2014). Increased urban heat may also have social and economic consequences such as by discouraging physical activity, reducing outdoor accessibility, and decreasing economic output (Stamatakis et al. 2013; Karner et al. 2015; Obradovich & Fowler 2017; Kjellstrom et al. 2009). Urban heat islands have been well documented in academic literature (Oke 1982; Arnfield 2003), and anthropogenic waste heat is often a major factor. The American Meteorological Society (2012) has said that anthropogenic waste heat may contribute “15 – 50 W/m2 to the local heat balance, and several hundred W/m2 in the center of large cities in cold climates and industrial areas.”

Anthropogenic waste heat from urban vehicle travel may be a notable contributor to the urban heat balance and the urban heat island effect, but little research has quantified and explored how changes in vehicle travel may influence local climates. Even with recent rapid improvements to engine efficiencies, modern automobiles still convert small amounts of fuel to useful energy. Typically, around two-thirds of energy from fuel in internal combustion engine vehicles is lost as waste heat through exhaust and coolant (Hsiao et al. 2010; Yu & Chau 2009; Saidur et al. 2009; Endo et al. 2007), and as much as 80% of fuel energy can be lost to waste heat under poor conditions (Orr et al. 2016). In addition, combustion of fuel generates water vapor and air pollution which may also affect the urban climate. Figure 1 displays where a typical combustion engine’s fuel energy is used and lost. There has been little research that quantifies the influence of vehicle travel on urban anthropogenic waste heat. According to Sailor and Lu (2004), most cities have peak anthropogenic waste heat values between 30 and 60 W m-2 (averaged across city) and heating from vehicles could make up as much as 62% of the total in summer months. Additionally, they found that vehicle waste heat could account for up to 300 W m-2 during rush hours over freeways. In another study, Hart & Sailor (2009) used in situ measurements in Portland, OR to evaluate spatial variability of air temperatures on urban roadways. They found that air masses near major roadways are some of the warmest in the region. Although some of the warming is attributed to pavement characteristics (imperviousness, low albedo), an average increase of 1.3 C was observed on weekdays relative to weekends along roadways. The authors offer increased weekday traffic density and building use as the likely contributors to this discrepancy. These previous studies indicates that vehicle related waste heat could be an important consideration in the urban energy balance. If significant, there may exist viable strategies to reduce anthropogenic waste heat from urban vehicle travel by increasing the fleet fuel economy and shifting to electric vehicles. This could offer cooling in urban areas around roadways were pedestrians are often found. Figure 2 visually demonstrates waste heat from vehicles (including an electric vehicle) in two thermal images.