Housing Unit Density Research Articles

Hazardous Waste Cleanup, Neighborhood Gentrification, and Environmental Justice: Evidence from Restricted Access Census Block Data

We test for residential sorting and changes in neighborhood characteristics in response to the cleanup of hazardous waste sites using restricted access fine-geographical-resolution block data. We examine changes between 1990 and 2000 in blocks within 5km of sites that are proposed to the National Priority List that fall in a narrow interval of Hazardous Ranking Scores, comparing blocks near sites that were cleaned with those near sites that were not. Cleanup leads to increases in population density and housing unit density; increases in mean household income and shares of college-educated; but also to increases in the shares of minorities.

Identification of Environmental Covariates of West Nile Virus Vector Mosquito Population Abundance

The rapid spread of West Nile virus (WNv) in North America is a major public health concern. Culex pipiens-restuans is the principle mosquito vector of WNv in the northeastern United States while Aedes vexans is an important bridge vector of the virus in this region. Vector mosquito abundance is directly dependent on physical environmental factors that provide mosquito habitats. The objective of this research is to determine landscape elements that explain the population abundance and distribution of WNv vector mosquitoes using stepwise linear regression. We developed a novel approach for examining a large set of landscape variables based on a land use and land cover classification by selecting variables in stages to minimize multicollinearity. We also investigated the distance at which landscape elements influence abundance of vector populations using buffer distances of 200, 400, and 1000 m. Results show landscape effects have a significant impact on Cx. pipiens-estuans population distribution while the effects of landscape features are less important for prediction of Ae. vexans population distributions. Cx. pipiens-restuans population abundance is positively correlated with human population density, housing unit density, and urban land use and land cover classes and negatively correlated with age of dwellings and amount of forested land.

The Built Environment and Location-Based Physical Activity

Studies of the built environment and physical activity have implicitly assumed that a substantial amount of activity occurs near home, but in fact the location is unknown. This study aims to examine associations between built environment variables within home and work buffers and moderate-to-vigorous physical activity (MVPA) occurring within these locations. Adults (n=148) from Massachusetts wore an accelerometer and GPS unit for up to 4 days. Levels of MVPA were quantified within 50-m and 1-km home and work buffers. Multiple regression models were used to examine associations between five objective built environment variables within 1-km home and work buffers (intersection density, land use mix, population and housing unit density, vegetation index) and MVPA within those areas. The mean daily minutes of MVPA accumulated in all locations=61.1+/-32.8, whereas duration within the 1-km home buffers=14.0+/-16.4 minutes. Intersection density, land use mix, and population and housing unit density within 1-km home buffers were positively associated with MVPA in the buffer, whereas a vegetation index showed an inverse relationship (all p<0.05). None of these variables showed associations with total MVPA. Within 1 km of work, only population and housing unit density were significantly associated with MVPA within the buffer. Findings are consistent with studies showing that certain attributes of the built environment around homes are positively related to physical activity, but in this case only when the outcome was location-based. Simultaneous accelerometer-GPS monitoring shows promise as a method to improve understanding of how the built environment influences physical activity behaviors by allowing activity to be quantified in a range of physical contexts and thereby provide a more explicit link between physical activity outcomes and built environment exposures.

Can the land tax help curb urban sprawl? Evidence from growth patterns in Pennsylvania

Urban sprawl has become a policy concern of national prominence. One tool that has been suggested for combating sprawl is the land or split-rate tax. In theory, such taxes can raise the ratio of housing capital to land. This in turn can raise the density of housing units where it is applied, if the average size of housing units does not increase enough to offset an effect on the number of housing units. This research explores these issues, looking at a panel of land uses and demographics in Pennsylvania. We confirm the theoretical prediction that the split-rate tax raises the capital/land ratio. We also find that the primary effect is in more housing units, rather than bigger units, suggesting the split-rate tax is potentially a powerful anti-sprawl tool. We find adoption of the split-rate tax increases the number of housing units, and that these units follow a more dense pattern of development.

Quantifying human disturbance in watersheds: Variable selection and performance of a GIS-based disturbance index for predicting the biological condition of perennial streams

Characterizing the relative severity of human disturbance in watersheds is often part of stream assessments and is frequently done with the aid of Geographic Information System (GIS)-derived data. However, the choice of variables and how they are used to quantify disturbance are often subjective. In this study, we developed a number of disturbance indices by testing sets of variables, scoring methods, and weightings of 33 potential disturbance factors derived from readily available GIS data. The indices were calibrated using 770 watersheds located in the western United States for which the severity of disturbance had previously been classified from detailed local data by the United States Environmental Protection Agency (USEPA) Environmental Monitoring and Assessment Program (EMAP). The indices were calibrated by determining which variable or variable combinations and aggregation method best differentiated between least- and most-disturbed sites. Indices composed of several variables performed better than any individual variable, and best results came from a threshold method of scoring using six uncorrelated variables: housing unit density, road density, pesticide application, dam storage, land cover along a mainstem buffer, and distance to nearest canal/pipeline. The final index was validated with 192 withheld watersheds and correctly classified about two-thirds (68%) of least- and most-disturbed sites. These results provide information about the potential for using a disturbance index as a screening tool for a priori ranking of watersheds at a regional/national scale, and which landscape variables and methods of combination may be most helpful in doing so.

An Exploration of the Effect of Housing Unit Density on Aspects of Residential Landscape Sustainability in England

Residential landscapes are crucial to achieving sustainable housing. However, there are concerns that higher housing densities will lead to unsustainable loss of gardens, greenspace and tree cover. This paper explores the effect of housing density on these variables, and finds that only garden provision is negatively correlated. Total greenspace cover need not decrease with densification if flats are combined with communal spaces. However, the quality of these spaces and their sustainable credentials were seen to be highly variable. Tree cover provided by developers is not related to density—they appear to be reluctant to plant trees across the density range.

Modelling housing unit density from land cover metrics: a Midwestern US example

Geographic applications frequently require the gathering and analysis of socioeconomic data. For many nations, these data are normally collected through a census. However, during the intercensal period (5–10 years), these data lose their currency and must be updated. The objective of this project was to estimate housing unit density from Landsat ETM+ imagery in the Terre Haute, IN, USA, region. Modelling was done for 1945 census blocks in the study area containing 30 972 housing units. Landtype, as represented by six cluster classes, was used as the primary surrogate for housing unit density. The percentage of each landtype within the census blocks was calculated. Other landscape metrics representing landtype patch dominance and diversity were also calculated on a per-block basis. Housing unit density within the census block was then modelled as a function of those percentages and metrics using discriminant analysis and multiple regression. The simple correlation between the observed and modelled housing unit density was 0.79. The mean residual error produced by the model was 0.37 housing units per hectare.

Can the Land Tax Help Curb Urban Sprawl? Evidence from Growth Patterns in Pennsylvania

Urban sprawl has become a policy concern of national prominence. Land or split-rate taxes are one potential way to address this issue. In theory, such taxes can raise the capital/land ratio. This in turn can raise the density of housing units where it is applied, if the average quality/size of each housing unit does not increase by enough to offset an effect on the number of housing units. This research explores these issues, looking at a panel of land uses and demographics in Pennsylvania. We confirm the theoretical prediction that the split-rate tax raises the capital/land ratio. We also find that the primary effect is in more housing units, rather than bigger or nicer units, suggesting the split-rate tax is potentially a powerful anti-sprawl tool.

Emergency Planning in the Urban-Wildland Interface: Subdivision-Level Analysis of Wildfire Evacuations

This project was motivated by recent research that has advocated the need for a better understanding of and planning for evacuations of residential subdivisions under threat from wildfires. Prior work has suggested that the density of housing units and ineffective evacuation routing and egress may have contributed to fatalities in subdivisions in which residents were unable to evacuate when the need arose. To evaluate the effects of development density and street network layout, this study utilized simulation to represent and evaluate various evacuation scenarios at the neighborhood level under ranges of housing density and threat urgency. The results of this study illustrate the relationships between the traffic that can be accommodated by a roadway network; the location and number of egress points; and the time during which vehicles enter and exit the network. Most significantly, it showed how changes in traffic volume need to be accompanied by corresponding increases or decreases in time and/or egress capacity to move evacuees out of the threat zone. Similarly, changes in the network (i.e., adding and/or modifying the location of exits) were also shown to significantly decrease evacuation clearance times and increase the total exiting traffic.

Neighborhood Environment and Adherence to a Walking Intervention in African American Women

This secondary analysis examined relationships between the environment and adherence to a walking intervention among 252 urban and suburban, midlife African American women. Participants received an enhanced or minimal behavioral intervention. Walking adherence was measured as the percentage of prescribed walks completed. Objective measures of the women's neighborhoods included walkability (land use mix, street intersection density, housing unit density, public transit stop density), aesthetics (physical deterioration, industrial land use), availability of outdoor (recreational open space) and indoor (recreation centers, shopping malls) walking facilities/spaces, and safety (violent crime incidents). Ordinary least squares regression estimated relationships. The presence of one and especially both types of indoor walking facilities were associated with greater adherence. No associations were found between adherence and other environmental variables. The effect of the enhanced intervention on adherence did not differ by environmental characteristics. Aspects of the environment may influence African American women who want to be more active.

Portable Global Positioning Units to Complement Accelerometry-Based Physical Activity Monitors

This study examines the usefulness of complementing accelerometry-based physical activity measurement with spatial data from portable global positioning system (GPS) units to determine where physical activity occurs. First, using the geographic distribution of data points and Bland-Altman plots, we examined GPS units' validity and interunit reliability by measuring the distance to a geodetic point. We also assessed interunit reliability by comparing GPS data collected in three built environment contexts. Second, we conducted a pilot study in which 35 participants wore GPS units and accelerometers in free-living conditions for 3 d. Moderate and vigorous physical activity (MVPA) bouts were matched to GPS data. We classified each bout as occurring inside or outside the participant's home neighborhood. Using unpaired t-tests and Fisher's exact tests, we compared neighborhood attributes for participants having the majority of MVPA bouts within their home neighborhood, relative to those with most bouts away from their home neighborhood. Average distance from each unit to the geodetic point was 3.02 m (SD 2.51). Average bias among units using Bland-Altman plots was 0.90 m, ranging from -0.22 to 1.86 m, within the limits of agreement. For interunit reliability in the built environment contexts, the mean distance difference among units ranged between 10.7 m (SD 11.9) and 20.1 m (SD 21.8). For the pilot study involving participants, GPS data were available for 59.3% of all bouts (67% of MVPA time), of which 46% were in the participants' neighborhood. Participants obtaining most of their MVPA in their neighborhoods tend to live in areas with higher population density, housing unit density, street connectivity, and more public parks. Data recorded by portable GPS units is sufficiently precise to track participants' movements. Successful matching of activity monitor and locational data suggests GPS is a promising tool for complementing accelerometry-based physical activity measures. Our pilot analysis shows evidence that the relationship between environment and activity can be clarified by examining where physical activity occurs.

The influence of surface characteristics on urban radiant temperatures

While the urban heat island is a well recognized and pervasive phenomenon, the less common condition of an urban heat sink has been observed in an Indianapolis case study. The authors have provided some explanatory basis for this anomaly largely with respect to variations in biomass and urban versus rural differences in thermal inertia resulting from variations in soil cover, moisture and density. Here specific attention is given to the influences of a variety of urban surfaces (residential, commercial, and industrial land uses) on the pattern of urban radiant temperatures exhibited by the Indianapolis heat sink. In addition, variations in the density of these land use forms are examined with respect to their influences on radiant temperatures. In all three land use categories, density variations demonstrate important influences on radiant temperatures. In the case of residential land use, the variable of housing unit density is strongly associated with radiant temperatures. The relationships exhibited by variations in commercial and industrial densities are more complex. They suggest that the prevailing heat sink at this specific point in time surrounded a heat island within the central business district. The thermal uniqueness of the central business district is most likely the result of relatively large proportions of “artificial surfaces” including older and heavier forms of construction. Physical explanation of the complex thermal patterns of the urban surface requires an understanding of the roles played by both thermal inertia and the biomass‐heat flux relationship.

Measurements of housing density along transmission lines.

One of the fundamental inputs to models of population exposure to the power-frequency fields of high-voltage transmission lines is the density of population about the lines. We examined aerial photographs of over 1,700 km of transmission corridor to characterize the density of nearby housing units. The data show that the density of houses within 200 m of transmission lines 1) is typically smaller than the average density of houses in the local utility's service area, 2) tends to increase with distance from the line, and 3) is inversely correlated with line voltage.

The effects of density and urban residence on voter turnout

The rate of voting in cities of the U.S. tends to be lower than one would expect when compared to nationwide voter participation rates. The hypothesis in question here is whether high population density and urbanness have a dampening effect on the likelihood of voting by persons living under such conditions. This question is examined by relating county voting rates in recent U.S. Presidential elections to various types of county population density, while controlling for fifteen potentially contaminating variables. The hypothesis that population density reduces voter turnout cannot be rejected on the basis of the test. There is a small but significant negative relationship between the press of population — represented by the population per square mile and urbanness — and voter turnout, even when the various control variables are present. More immediate types of density, such as housing unit and room density, appear to be insignificant. Possible reasons for the results are discussed.