Wasatch Front Research Articles

Late Pleistocene Record of Off‐Fault Deformation and Vertical Slip Rates from the Wasatch Fault Zone, Utah: Implications for Fault Segmentation from Lake Bonneville Shorelines

AbstractIn an effort to better understand the Pleistocene history of the Wasatch fault zone, we evaluate the deformation and displacement of the Bonneville and Provo high‐stand shorelines of Lake Bonneville along the Wasatch Front. We apply an automated shoreline elevation measurement application developed as part of this study to measure Lake Bonneville shoreline elevations along the Weber and Brigham City segments of the fault, adding to a previously published dataset of shoreline elevations on the Salt Lake City segment. Tectonically deformed shorelines on the footwall of the fault demonstrate elevation patterns that are inconsistent with the idea that the Pleasant View salient, a bedrock salient marking the segment boundary between the Weber and Brigham City segments of the fault, is a persistent barrier to fault rupture since the late Pleistocene. Shoreline features are elevated ∼20 m across the segment boundary as compared to shoreline features on the northern part of the Brigham City segment. We suggest the possibility that fault rupture through the Pleasant View salient has been common since the late Pleistocene and speculate that a similar relationship could exist between the Provo and Salt Lake City segments, based on similarities between the shoreline elevation patterns on the Brigham City and Salt Lake City segments of the fault. Vertical slip rates measured from displaced shorelines at the Pleasant View salient (Brigham City–Weber segment boundary) are generally higher compared to those at the Honeyville spur (Collinston–Brigham City segment boundary). Statistically significant vertical slip rates calculated from the Provo shoreline at the Pleasant View salient (0.8±0.5 to 0.9±0.6 mm/yr and 0.7±0.5 to 0.9±0.6 mm/yr) suggest that late Pleistocene vertical slip rates are slightly lower than Holocene rates; however, large uncertainties in the shoreline elevation measurements exist.

Trace element chemistry of atmospheric deposition along the Wasatch Front (Utah, USA) reflects regional playa dust and local urban aerosols

Atmospheric deposition to urban areas and mountain snowpack often contains a mixture of playa dust and anthropogenic aerosols, yet the relative contribution of trace elements from each source is not well understood. To evaluate dust contributions from regional playas to an urban area, we sampled playa dust sources, urban dust deposition, and snow dust deposition across the Wasatch Front in northern Utah, USA. Dust samples were analyzed for trace and major element chemistry, grain size distribution, and mineralogy. Playa, urban, and snow dust samples contained similar mineralogy, dominated by silicate, carbonate, and evaporite minerals. Grain size distribution between playa, urban, and snow dust samples was also similar, suggesting that playas are a primary dust source for the region. Principal component analysis and enrichment diagrams revealed similar chemistry of playa, urban, and snow dust with some exceptions. Compared with playa dust, urban and snow dust had lower concentrations of Li, Na, Sr, U, Mg, and Ca and higher concentrations of Fe, Al, Be, Sb, Se, Mo, Cr, La, and Cu. The first set of elements are found in evaporite- and carbonate-minerals while the second set of elements are sourced from anthropogenic activities. Mass balance calculations suggest that 90% of the dust mass deposited to the Wasatch Front is from playas, with small additions from local sources that alter the dust chemistry. Sequential leaching of dust samples showed that some elements were readily leached with weak acids, including B, K, Na, Sr, Ca, U, Mo, Cd, and Se, suggesting that they are environmentally available and may serve as important macronutrients or contaminants to ecosystems. This is the first study to directly compare the geochemistry of playa dust sources with dust deposition to urban areas and mountain snowpack in the western US, with implications for understanding how water diversions, land use changes, and population growth may affect the regional dust cycle in the future.

Modeling net effects of transit operations on vehicle miles traveled, fuel consumption, carbon dioxide, and criteria air pollutant emissions in a mid-size US metro area: findings from Salt Lake City, UT

The Utah Transit Authority (UTA) serves Utah’s Wasatch Front, a rapidly growing conurbation with a current population of ∼1.8 M people. UTA uses an electronic fare collection (EFC) system that requires riders to tap on as they enter a bus or train and tap off as they exit, as well as an automated passenger counter (APC) system that counts interruptions of infrared beams across vehicle doorways as riders board and alight. We analyzed EFC and APC data for 2016, along with service schedules and routes from General Transit Feed Specification (GTFS) data, to estimate the impact of UTA on the air quality in its service region by accounting for vehicle miles traveled, gasoline gallons equivalent of fuel consumed, and multiple pollutant species emitted. Buses, light rail, and commuter rail were found to collectively offset approximately 1.5% of the onroad emissions from the counties served by UTA due to transit use replacing single passenger vehicle use. These offsets are not homogeneous; ridership drops significantly (∼20%–50% depending on the mode) during the summer months as some of the largest users are educational institutions with noticeable seasonal cycles. Low transit use during the weekend negates some of the air quality benefits as buses and trains travel at lower capacity. Central routes, particularly during peak travel hours provide noticeable congestion, fuel consumption, and pollutant emissions reduction due to trips taken by transit replacing personal vehicles but off-peak, and non-central routes, show lower benefits. Because the light rail is electric, its local air quality benefits are significant due to the electricity being produced primarily outside the airshed. Upgrading the bus fleet to 2010 model, and newer, diesel and compressed natural gas (CNG) buses, as well as modeling an envisioned change to Tier 3 locomotives for the commuter rail system, was found to significantly reduce regional nitrogen oxides (NOx), fine particulate matter (PM2.5), and sulfur oxides (SOx) emissions.

A Novel, Highly Related Jumbo Family of Bacteriophages That Were Isolated Against Erwinia.

Erwinia amylovora is a plant pathogen from the Erwiniaceae family and a causative agent of the devastating agricultural disease fire blight. Here we characterize eight lytic bacteriophages of E. amylovora that we isolated from the Wasatch front (Utah, United States) that are highly similar to vB_EamM_Ea35-70 which was isolated in Ontario, Canada. With the genome size ranging from 271 to 275 kb, this is a novel jumbo family of bacteriophages. These jumbo bacteriophages were further characterized through genomic and proteomic comparison, mass spectrometry, host range and burst size. Their proteomes are highly unstudied, with over 200 putative proteins with no known homologs. The production of 27 of these putative proteins was confirmed by mass spectrometry analysis. These bacteriophages appear to be most similar to bacteriophages that infect Pseudomonas and Ralstonia rather than Enterobacteriales bacteria by protein similarity, however, we were only able to detect infection of Erwinia and the closely related strains of Pantoea.

Supporting Public Lands in an Uncertain Age: The Wasatch Front Urban Ranger Program

Open space and parks in urban and urban-proximate areas provide vital social, economic, and health benefits to people and communities. Specific benefits include offering opportunities for people to connect with nature, improving air quality, supporting wildlife habitat, and improving community identity and attachment. Management and maintenance of these areas can be expensive and challenging, particularly when multiple agencies oversee different components of the same resource. In the Salt Lake Valley in Utah, the Jordan River Parkway (JRP) and the Bonneville Shoreline Trail (BST) provide recreation opportunities to local citizens. Multiple agencies and private land owners are charged with managing elements of each entity, resulting in inconsistent application of management plans including patrols and maintenance. Subsequently, there are aspects of these outdoor recreation spaces that need increased support, maintenance, and overall stewardship. In 2015, the Department of Parks, Recreation, and Tourism at the University of Utah and the National Park Service’s Rivers, Trails, and Conservation Assistance Program (RTCA) created the Wasatch Front Urban Ranger Program (WFURP), a trail ambassador program featuring student volunteers from the University of Utah. Each Urban Ranger has three primary duties: public engagement, performing light maintenance, and collecting data on various aspects of trail use. During daily patrols, Rangers inform the public of land management issues and direct them to appropriate resources. They perform trail maintenance, including removing litter, cleaning dog waste, and plucking noxious weeds. They collect data about visitor use and conditions in each area, and regularly report the data to respective management agencies and/or law enforcement and health officials. Rangers recruit a student volunteer for each patrol, which helps increase engagement and enhance knowledge about public lands issues among University students. The program is funded through a number of small grants and the majority of the funding supports a graduate student to coordinate the program. Program partners include the National Park Service (NPS), Bureau of Land Management (BLM), Jordan River Commission (JRC), and Utah Department of Natural Resources (DNR). Support from additional local and national agencies help train the Rangers, including personnel the Salt Lake City Open Space District, the U.S. Fish and Wildlife Service, the USDA Forest Service (USFS), and local law enforcement agencies. Subscribe to JPRA

Access to Soft-Surface, Green Exercise Trails in Mountainous, Urban Municipalities.

Soft-surface exercise infrastructure (ie off-road, mountain, and dirt trails) has been a particularly valuable community asset in mountainous, urban municipalities. This off-road, trail infrastructure can encourage individuals to engage in green exercise (ie physical activity done outside while in nature, for example, mountainous trails and near waterways). Green exercise can be helpful for encouraging individuals to participate in exercise who otherwise may not; it is especially helpful for promoting mental well-being and a sense of being connected to the environment. This study characterizes trail access and predictors among urban, mountainous municipalities in the Utah Wasatch Front region. Access was determined using two-standard deviation ellipses (2SDE) activity space analysis, and predictors were identified using multiple linear regression. About 42% municipalities had no trailhead access (ie no trailhead within its corresponding activity space). Trail density and trailheads were significantly correlated (r = 0.49, P = .004). There was a significant trail density cluster in the southern area of the study region, centered all over the city of Alpine. Reduced-model regression yielded trailheads and home income as being significant predictors of trail density, and trail density and elevation as being significant predictors for trailheads. Results demonstrate patterns of access to green exercise trails that align with socioeconomic and municipal elevation. The results of this research should be insightful for those who work in exercise promotion and urban planners.

Acute effects of air pollutants on spontaneous pregnancy loss: a case-crossover study

To investigate the relationship between acute exposure to air pollutants and spontaneous pregnancy loss. Case-crossover study from 2007 to2015. An academic emergency department in the Wasatch Front area of Utah. A total of 1,398 women who experienced spontaneous pregnancy loss events. None. Odds of spontaneous pregnancy loss. We found that a 10-ppb increase in 7-day average levels of nitrogen dioxide was associated with a 16% increase in the odds of spontaneous pregnancy loss (odds ratio [OR] = 1.16; 95% confidence interval [CI] 1.01-1.33; P=.04). A 10-μg/m3 increase in 3-day and 7-day averages of fine particulate matter were associated with increased risk of spontaneous pregnancy loss, but the associations did not reach statistical significance (OR3-day average = 1.09; 95% CI 0.99-1.20; P=.05) (OR7-day average = 1.11; 95% CI 0.99-1.24; P=.06). We found no evidence of increased risk for any other metrics of nitrogen dioxide or fine particulate matter or any metric for ozone. We found that short-term exposure to elevated levels of air pollutants was associated with higher risk for spontaneous pregnancy loss.

Genome Sequences of Nine Erwinia amylovora Bacteriophages.

Erwinia amylovora is a plant pathogen belonging to the Enterobacteriaceae family, a family containing many plant and animal pathogens. Herein, we announce nine genome sequences of E. amylovora bacteriophages isolated from infected apple trees along the Wasatch Front in Utah.

Short-Term Elevation of Fine Particulate Matter Air Pollution and Acute Lower Respiratory Infection.

Nearly 60% of U.S. children live in counties with particulate matter less than or equal to 2.5 μm in aerodynamic diameter (PM2.5) concentrations above air quality standards. Understanding the relationship between ambient air pollution exposure and health outcomes informs actions to reduce exposure and disease risk. To evaluate the association between ambient PM2.5 levels and healthcare encounters for acute lower respiratory infection (ALRI). Using an observational case-crossover design, subjects (n = 146,397) were studied if they had an ALRI diagnosis and resided on Utah's Wasatch Front. PM2.5 air pollution concentrations were measured using community-based air quality monitors between 1999 and 2016. Odds ratios for ALRI healthcare encounters were calculated after stratification by ages 0-2, 3-17, and 18 or more years. Approximately 77% (n = 112,467) of subjects were 0-2 years of age. The odds of ALRI encounter for these young children increased within 1 week of elevated PM2.5 and peaked after 3 weeks with a cumulative 28-day odds ratio of 1.15 per +10 μg/m3 (95% confidence interval, 1.12-1.19). ALRI encounters with diagnosed and laboratory-confirmed respiratory syncytial virus and influenza increased following elevated ambient PM2.5 levels. Similar elevated odds for ALRI were also observed for older children, although the number of events and precision of estimates were much lower. In this large sample of urban/suburban patients, short-term exposure to elevated PM2.5 air pollution was associated with greater healthcare use for ALRI in young children, older children, and adults. Further exploration is needed of causal interactions between PM2.5 and ALRI.

Aeolian dust chemistry and bacterial communities in snow are unique to airshed locations across northern Utah, USA

Wind-blown dust is an important source of trace metals, nutrients, and biological material to montane ecosystems. Mountain ranges in northern Utah are located downwind of multiple dust sources including the Great Basin Desert and the Wasatch Front urban area, providing an opportunity to investigate regional-scale differences in dust deposition chemistry and bacterial composition. We sampled discrete dust layers from snowpack across multiple locations in the Wasatch and Uinta Mountains (Utah) and the Snake Range (Nevada) during spring 2014 and 2015. Dust chemistry was unique in each airshed, suggesting that spatial variability and local sources were more important than temporal variability for the sampling period. The central Wasatch dust contained the highest concentrations of playa-associated elements (U, Mg, Li, Ca, Sr, As) and anthropogenic elements (Sb, Cu, Pb, Se) compared with lowest concentrations of these elements in the northern Wasatch, which is further from playa and anthropogenic sources. Sequential extractions indicate that the majority of Ca, Sr, and Cd is potentially available for transport during snowmelt while other elements are relatively immobile. Central Wasatch dust was more reactive to acetic acid than northern Wasatch dust for most elements, including REE + Y. Sr isotopes (87Sr/86Sr ratios) were also unique to each sampling area, with the most radiogenic values in the central Wasatch. Similar to dust chemistry, bacterial communities in dusty snow reflected geographically localized dust events. In the central Wasatch, 69% of bacterial species were unique, suggesting that the airshed received the most diverse dust inputs from a combination of playa and anthropogenic sources. Gram-positive Actinobacteria and Firmicutes were common in snow but specific bacterial families distinguished airsheds (e.g., Bacillaceae, Geodermatophilaceae, Nakamurellaceae). Our results demonstrate that evaluating dust chemistry and bacteria in snow on a regional scale may more clearly link dust sources to the entrainment of pollutants and seeding of bacteria species to montane systems.

Social Dimensions of Urban Flood Experience, Exposure, and Concern

AbstractWith growing urban populations and climate change, urban flooding is an important global issue, even in dryland regions. Flood risk assessments are usually used to identify vulnerable locations and populations, flooding experience patterns, or levels of concern about flooding, but rarely are all of these approaches combined. Furthermore, the social dynamics of flood concerns, exposure, and experience are underexplored. We combined geographic and survey data on household‐level measures of flood experience, concern, and exposure in Utah's urbanizing Wasatch Front. We asked: (1) Are socially vulnerable groups more likely to be exposed to flood risk? (2) How common are flooding experiences among urban residents, and how are these experiences related to sociodemographic characteristics and exposure? and (3) How concerned are urban residents about flooding, and does concern vary by exposure, flood experience, and sociodemographic characteristics? Although floodplain residents were more likely to be White and have higher incomes, respondents who were of a racial/ethnic minority, were older, had less education, and were living in floodplains were more likely to report flood experiences and concern about flooding. Flood risk management approaches need to address social as well as physical sources of vulnerability to floods and recognize social sources of variation in flood experiences and concern.

Applying Innovative Performance Metrics for Corridor Evaluation

Widespread application of traditional performance metrics such as vehicle level of service has resulted in transportation networks that are often suited for only one mode of transportation to the detriment of others. Moreover, the continued investment in capacity expansion intended to meet level of service expectations increases financial burdens on transportation agencies for the capital, operating, and maintenance costs of these facilities, without regard to whether those resources are being used efficiently. Shifting focus to alternative and more comprehensive performance metrics can result in a more economical approach to transportation infrastructure, allowing communities to understand what investment combinations provide the best bang for the buck. Innovative performance metrics also allow communities to consider priorities beyond level of service, and design infrastructure accordingly. The Wasatch Front Central Corridor Study, undertaken in the Salt Lake City metropolitan area, is one example of a regional application of efficiency-focused performance metrics such as person throughput, seat utilization, benefit–cost ratio, access to employment, and economic impacts. Further research opportunities could include development of best practices to standardize benefit–cost analysis for transportation projects, other methods of evaluating overall system efficiency, and the role of parking policy and land use change in maximizing use of transportation resources.

A Community Needs Assessment of Urban Utah American Indians and Alaska Natives.

The needs of Urban American Indian/Alaska Native (AI/AN) populations are often not well understood. In order to inform programs and services, the Urban Indian Center of Salt Lake (UIC-SL), in cooperation with researchers from the University of Utah, undertook a community needs assessment of AI/AN living along Utah's Wasatch Front. A 60-item questionnaire was developed to capture information about health status, services used, unmet needs, and common sources of information about AI/AN community events and activities. Study participants (n = 336) were a convenience sample. Descriptive statistics, including mean, standard deviation, percentage, and 95% confidence intervals, were calculated. The most common health provider diagnosed medical conditions included hypertension, obesity, and diabetes. The prevalence of violence, substance abuse, and mental health conditions were also high among study participants and their families. Compared to the general Utah population, study participants experienced disparities relative to diabetes prevalence, cognitive and visual disabilities, and access to health care. In addition to health care services, respondents indicated a need for cultural, social, and educational programs. They also reported high levels of technology use, suggesting a possible avenue for communicating with this population. This community-based participatory research project provided rich information about the unmet needs of this urban AI/AN population. The results will be used to guide UIC-SL strategic planning, and a database created for this project will be available for future data collection, allowing for comparison of results between sites and over time.

A multi-factor GIS method to identify optimal geographic locations for electric vehicle (EV) charging stations

Abstract. Fuel-based transportation is one of the major contributors to poor air quality in the United States. Electric Vehicle (EV) is potentially the cleanest transportation technology to our environment. This research developed a spatial suitability model to identify optimal geographic locations for installing EV charging stations for travelling public. The model takes into account a variety of positive and negative factors to identify prime locations for installing EV charging stations in Wasatch Front, Utah, where automobile emission causes severe air pollution due to atmospheric inversion condition near the valley floor. A walkable factor grid was created to store index scores from input factor layers to determine prime locations. 27 input factors including land use, demographics, employment centers etc. were analyzed. Each factor layer was analyzed to produce a summary statistic table to determine the site suitability. Potential locations that exhibit high EV charging usage were identified and scored. A hot spot map was created to demonstrate high, moderate, and low suitability areas for installing EV charging stations. A spatially well distributed EV charging system was then developed, aiming to reduce “range anxiety” from traveling public. This spatial methodology addresses the complex problem of locating and establishing a robust EV charging station infrastructure for decision makers to build a clean transportation infrastructure, and eventually improve environment pollution.

Short-Term Air Pollution and Incident Pneumonia. A Case-Crossover Study.

The relationship between air pollution and pneumonia is poorly understood. To examine relationships between short-term air pollution exposure and number and severity of pneumonia cases along the Wasatch Front in Utah, a region with periodic high levels of outdoor air pollution. We applied time-stratified case-crossover analyses with distributed lag to patients presenting to seven emergency departments with pneumonia over a 2-year period. We compared levels of particulate matter less than or equal to 2.5 μm in aerodynamic diameter, nitrogen dioxide, and ozone at patient residences with emergency department cases, hospitalizations, objectively defined severe pneumonia, and mortality. We calculated direct cost impacts of particulate matter less than or equal to 2.5 μm in aerodynamic diameter reduction. We evaluated 4,336 pneumonia cases in seven hospitals. Among adults aged 65 years and older, we found consistently positive associations between particulate matter less than or equal to 2.5 μm in aerodynamic diameter within 6 days of presentation and instances of pneumonia (Lag Day 1 adjusted odds ratio, 1.35 per 10 μg/m3 over 12 μg/m3; 95% confidence interval, 1.16-1.57), severe pneumonia (Lag Day 1 adjusted odds ratio, 1.38; 95% confidence interval, 1.06-1.80), and inpatient mortality (Lag Day 5 adjusted odds ratio, 1.50; 95% confidence interval, 1.03-2.16). Smaller associations were found between nitrogen dioxide exposure and pneumonia occurrence, severity, and inpatient and 30-day mortality. Ozone exposure was modestly associated with increased instance and severity of pneumonia in younger adults. Particulate matter less than or equal to 2.5 μm in aerodynamic diameter and nitrogen dioxide effects were greatest in colder months, and ozone effects were greatest in warmer months. Reduction of particulate matter less than or equal to 2.5 μm in aerodynamic diameter levels to less than 12.0 mg/m3 could prevent 76-112 cases of pneumonia per year in these hospitals serving approximately half of the Wasatch Front's population, reducing direct medical facility costs by $807,000 annually. Among older adults, short-term ambient particulate matter less than or equal to 2.5 μm in aerodynamic diameter exposure is associated with more emergency department visits and hospitalizations for pneumonia, severe pneumonia, increased mortality, and increased healthcare costs. Nitrogen dioxide and ozone modestly increase pneumonia risk and illness severity.

Genome Sequences of 19 Novel Erwinia amylovora Bacteriophages.

ABSTRACTErwinia amylovora is the causal agent of fire blight, a devastating disease affecting some plants of the Rosaceae family. We isolated bacteriophages from samples collected from infected apple and pear trees along the Wasatch Front in Utah. We announce 19 high-quality complete genome sequences of E. amylovora bacteriophages.

Evaluating public transit services for operational efficiency and access equity

Assessing the performance of public transit services has long been an important yet challenging issue for transportation agencies and researchers. Transit service performance measurement reflects a very first step towards an efficient and proactive management, where public transit agencies are increasingly pressured to provide high-quality services in spite of constrained resources. However, the performance evaluation of transit services is complicated by an array of quantitative measures available to assess the goals and the diversity in the goals themselves, which usually include improving operational efficiency and providing equitable access. While much previous work has examined public transit services for achieving optimal operational efficiency and/or access equity separately, the interplay of the two has rarely been investigated to date. This article proposes a new method for evaluating the overall performance of public transit services via a combination of data envelopment analysis (DEA), Geographic Information System (GIS), and multi-objective spatial optimization techniques. The new method is applied to assessing the performance of fixed route bus services operated by the Utah Transit Authorities (UTA) in the Wasatch Front, Utah. Results demonstrate that the proposed method can effectively account for operational efficiency and access equity in an integrated framework, providing a more comprehensive assessment for transit service performance.

The CAA Motor Vehicle Inspection and Maintenance Program: Is it Cost Effective?

Under the Clean Air Act, state-run vehicle inspection and maintenance (I/M) programs aim at preventing both manufacturers and consumers from circumventing or tampering with emissions control technology. Recent manufacturer cheating scandals, however, were detected by means other than I/M programs, and much I/M enforcement has been targeted at relatively low-level offenses. This Article traces the evolution of the I/M program and examines whether it currently provides benefits greater than its costs to vehicle owners, using Utah’s Wasatch Front (which includes Salt Lake City) to illustrate how the program operates in practice. It concludes that there is little current information to support or reject the efficacy of the I/M program, and that a fresh look is warranted to improve its effectiveness.

Wind-Blown Dust Modeling Using a Backward-Lagrangian Particle Dispersion Model

AbstractPresented here is a new dust modeling framework that uses a backward-Lagrangian particle dispersion model coupled with a dust emission model, both driven by meteorological data from the Weather Research and Forecasting (WRF) Model. This new modeling framework was tested for the spring of 2010 at multiple sites across northern Utah. Initial model results for March–April 2010 showed that the model was able to replicate the 27–28 April 2010 dust event; however, it was unable to reproduce a significant wind-blown dust event on 30 March 2010. During this event, the model significantly underestimated PM2.5 concentrations (4.7 vs 38.7 μg m−3) along the Wasatch Front. The backward-Lagrangian approach presented here allowed for the easy identification of dust source regions with misrepresented land cover and soil types, which required an update to WRF. In addition, changes were also applied to the dust emission model to better account for dust emitted from dry lake basins. These updates significantly improved dust model simulations, with the modeled PM2.5 comparing much more favorably to observations (average of 30.3 μg m−3). In addition, these updates also improved the timing of the frontal passage within WRF. The dust model was also applied in a forecasting setting, with the model able to replicate the magnitude of a large dust event, albeit with a 2-h lag. These results suggest that the dust modeling framework presented here has potential to replicate past dust events, identify source regions of dust, and be used for short-term forecasting applications.

A spatio-temporal accessibility measure for modelling activity participation in discretionary activities

Accessibility is a key indicator for the number of opportunities experienced by an individual, and it is generally assumed that higher levels of accessibility lead to higher levels of activity participation and satisfaction. Despite the fact that this relationship has been tested in preceding studies, no clear pattern of correlation has been found between an individual’s accessibility and his/her participation in out-of-home discretionary activities. Previous studies mostly applied aggregate, spatial accessibility measures that do not account for the heterogeneity related to an individual’s spatio-temporal constraints. However, in addition to locations’ spatial distribution, personal constraints related to the mandatory activities a person undertakes – and therefore, his/her available time budget throughout the day – impact activity choices and scheduling. This paper proposes a disaggregate, person-based accessibility measure that takes spatial and temporal constraints into consideration for the travel behavior of 11,599 individuals in the Wasatch Front region, Utah. This method is compared to an aggregate, home-based accessibility measure to assess both methods’ ability to predict activity participation. The results show a highly significant, moderate correlation between the proposed person-based accessibility measure and participants’ surveyed partaking in discretionary activities. Both the model prediction and the locally weighted regression smoother indicate that the greatest change in participation occurs within the mid-range of accessibility levels, and not in the low end of the accessibility range as was expected. In addition, the home-based method shows a negative and highly significant relationship to activity participation, which indicates that aggregate accessibility measures may provide counterintuitive findings.