SOUTH UTAH COUNTY EXPRESSWAY
Design - Alexander Barton
Model
Costs associated with wetlands, existing roads, parcels, and slope were inserted into a computer model and weighted according to certain criteria (see Figure 1). Two minimal cost paths (presented in Figure 2) were suggested by the model according to these criteria. The cost paths served as reference points from which the actual expressway route was drawn.
Both cost paths and the final expressway route were restricted to a predetermined study area, which measured approximately 11 miles north to south and 17 miles east to west. The study area is located in southern Utah County, encompassing the communities of Spanish Fork, Payson, Salem, Woodland Hills, Elk Ridge, and Mapleton. This region is expected to experience rapid population growth in the next 25 years.
Decision-makers preparing for this population growth have identified the need for new roads in southern Utah County, particularly an expressway which may reduce travel times to important arterials for residents of Elk Ridge and Woodland Hills. These maps and models are provided with the intent of giving decision-makers a detailed look at the process behind determining a preferred route.
Once costs were considered, I created a model in ArcGIS to analyze and predict the best potential expressway routes.
Figure 1. This computer model generated suggested minimal cost paths based on wetlands, slope, parcel, and road data.
Figure 2. Cost paths estimate the least cost routes to each destination according to a weighted model containing information about wetlands, slope, roads, and parcels. The calibrated cost layer (in green) guides the model as it selects routes, avoiding darker areas (which indicate areas of high cost) and trending toward lighter areas (which indicate areas of low cost). Note the large "holes" in the eastern and western sections of the study area; these are areas of high slope unsuitable for an expressway.
Preferred Route
While the cost paths served as a useful reference against which to build a new expressway, knowledge of the study area and needs pursuant to population growth influenced my decision to modify the preferred route. The route is essentially an approximation of the two cost paths, running between the paths on its way to I-15 (where it forms a new interchange) and, at the other end of the study area, on its way to U.S. Hwy 6. The only significant deviation is in the south part of the study area near Woodland Hills, where I chose to take the expressway further south than the model suggested in an effort to reduce the number of homes requiring demolition and to limit the number of intersections, thus maximizing traffic throughput.
Figure 3. The preferred route (in red) with minimal cost paths (in lime green and magenta) and a legend indicating significant changes in the study area (new intersections and bridges, demolished homes and roads, etc.) These data were imported into an interactive map, which can be viewed here.
While the preferred route is not without its problems - some homes will need to be demolished to make way for the road, and the project is likely to be expensive - it represents perhaps the best possible route according to the criteria selected for the project: limit the number of homes requiring demolition, limit the number of intersections along the expressway, and reduce construction costs. The preferred route can be viewed in an interactive map.
