Incorporating the Costs of Access Management to the Prioritization of Transportation Corridors Vulnerable to Land Development

Transcription

1 Incorporating the Costs of Access Management to the Prioritization of Transportation Corridors Vulnerable to Land Development Gavin W. Schmidt, Stephanie M. Rash, Luke R. Kincaid, Elmer K. Kim and James H. Lambert, Senior Member, IEEE Abstract A transportation agency has elected to prioritize the needs to protect corridors and corridor sections that are most vulnerable to land development. An existing methodology developed at the University of Virginia has begun to use parcel assessments, parks and schools, conservation easements, population data, employment data, and associated modeling and analysis to develop a priority score useful to screen among vulnerable corridor sections. This paper contributes data collection and analysis of the potential costs of access management and corridor protection along thirty-mile corridors. The costs are represented by (i) parcel values adjacent to half-mile corridor sections, and (ii) driveways, intersections, and other access points in the corridor sections. We discuss the demonstration of the extended methodology in a Virginia locality using a geographic information system. The extended methodology enables localities and transportation planners to address needs for corridor protection along many miles of corridor in a 60,000 mile statewide transportation system. software suite, ArcGIS 9.2, was developed at the University of Virginia to visually indicates the relative vulnerabilities of half-mile highway corridor sections. Fig. 1 is an overview of the steps of the existing methodology. Fauquier County was used as a case study for the methodology. However, the I. INTRODUCTION A. Problem HE Virginia Department of Transportation (VDOT) T supports localities and their planners in right-of-way (ROW) acquisition and other methods of access management in its maintenance and operations of 60,000 miles of roadway across the Commonwealth of Virginia. Rapid economic development often leads to the creation of new access points, thus increasing the amount of congestion. Localities would benefit from the use of a systematic approach to predict vulnerability to future development so improvements could be made to the transportation corridor before residential and commercial development makes access management infeasible. An existing methodology using a geographical mapping Manuscript received April, 7, This work was supported in part by the Virginia Department of Transportation and the Virginia Transportation Research Council. Gavin W. Schmidt is with the University of Virginia, Charlottesville, VA USA ( gws2p@virginia.edu) Stephanie M. Rash is with the University of Virginia, Charlottesville, VA USA ( smr5u@virginia.edu) Luke R. Kincaid is with the University of Virginia, Charlottesville, VA USA ( lrk6e@virginia.edu) Elmer K. Kim is with the University of Virginia, Charlottesville, VA USA ( ek2f@virginia.edu) James H. Lambert is the Associate Director of Center for Risk Management of Engineering Systems, University of Virginia, Charlottesville, VA USA ( lambert@virginia.edu) Fig. 1. Existing methodology prioritizing half-mile transportation corridor sections vulnerable to land development existing methodology did not provide information for making management decisions. While the existing methodology indicates vulnerability to development, without knowledge of the number of access points and the current value per acre VDOT planners could not determine the most beneficial corridors to protect. The value per acre of land would provide VDOT with an estimate for the cost of right-of-way acquisition and the number of access points was essential for determining the benefits of access management. B. Purpose The purpose of this effort is to collect and test the use of data layers that indicate the relative costs of access management across half-mile corridor sections. These layers include current location of high- and low-volume access points and the current cost-per-acre of land adjacent to the corridor. Knowledge of the location and magnitude of access points will allow VDOT to assess the feasibility of access management. Knowledge of the cost-per-acre will allow VDOT to assess the feasibility of ROW acquisition.

2 C. Benefits The effort will aid VDOT planners in making decisions regarding resource allocation for corridor protection. These tools can be used to provide quantitative support for the intuitions of VDOT planners about corridors to protect. VDOT can also be more proactive and avoid the costly investments of improving the roads after development has occurred. In addition to VDOT s benefits, road users will have a more enjoyable driving experience, access points can be restricted before they are created, and less residents and businesses will need to relocate in order for VDOT to expand the transportation corridor. D. Scope This effort was an extension to the case study in Fauquier County, Virginia, using the existing methodology. This effort did not seek to analyze the entire county, but rather to prove that the management layers could be created. Thus, we focused on a single major corridor: US Route 28. high volume and low volume. High volume access points are breaks in the corridor where the corridor is either (i) accessed by 5 or more houses, (ii) intersecting another major corridor, (iii) or is an entrance or exit to a major establishment such as a McDonalds, Walmart, or gas stations. Low volume access points are breaks in corridors which do not fall under the above requirements such as dirt roads. Thus to associate type of access points a "Volume" field is created in the attribute table. For every access point event, an appropriate volume is assigned: "0" for low volume and a "1" for high volume. C. Calculating Average Priority Score In order to determine the average priority score for each half-mile section of US Route 28, the buffered US 28 shapefile and the Priority Score Map were imported into ArcMap. Next, the priority scores for each parcel were multiplied by the parcel's total area in order to weight the scores by parcel size. Then, priority features from the II. METHODS A. Preparing US Route 28 The US Route 28 corridor must be prepared by (i) creating a consistent unidirectional polyline layer of US 28, (ii) splitting up the road into half-mile sections, and (iii) making 250-foot buffers around these half-mile sections. First, the transportation network of Virginia is imported into the ArcMap program. Only the corridor sections of US 28 that are within Fauquier County are selected. Since the corridor segments are not drawn orderly, a new unidirectional polyline is sketched along the US 28 centerline, with the sketch tool, starting from the east end to the west end of Fauquier County. Second, the unidirectional road of US 28 is split up into half-mile sections. This is accomplished by specifying the resolution of 0.5 miles using the proportion tool, which creates 28 half-mile sections. Third, the half-mile sections of US 28 are buffered 250 feet on either side. The buffers are created with flat edges as specified by buffer tool. B. Preparing Access Points Prior to this effort, access point data have not been collected, created, or characterized. The following addresses the steps taken in creating access point shapefiles and characterizing the types of access points. The aerial geographic photos of Fauquier County and the polyline shapefile of US 28 are imported into ArcMap and entered into editing mode. Starting from the west end of US 28, the snap tool is used to create a point for every occurrence of an access point, as shown as points in Fig. 2. An access point is any point along a corridor where an intersecting access occurs such as a driveway, dirt road, entrance/exit, or other major road. This snapping process is continued until the east end of US Route 28 is reached. Next, the access points are characterized by intensity of traffic volume into two types: Fig. 2. Eight access points highlighted along a corridor section of US Priority Score Map were joined to the 250-foot buffered road to associate the surrounding priority within the vicinity. This process resulted in a shapefile and a database file which include the (i) sum of parcel-size weighted priority scores within the 250-foot buffer for each half mile section and (ii) sum of the area of all parcels within the buffer. The database file is imported into a spreadsheet program and the average priority per half mile section is calculated. The average priority is calculated by dividing the weighted priority scores by the sum of the total area of all parcels within a 250 foot vicinity along half a mile. The resulting priority scores are then normalized from zero to three to be consistent with the scale used in the existing methodology.

3 D. Calculating Number of Access Points Access point counts and types are calculated by importing the buffered US 28 shapefile and the US 28 access point shapefile in ArcMap. The volume features from the access point layer were joined to the buffered road. This process resulted in a shapefile and a database file which include the (i) counts of access points of both high and low volume types and (ii) sum of volume within the 250 ft buffer for each half mile section. Since we defined high volume access points as "1" and low volume access points as "0", the database file is analyzed using a spreadsheet program to calculate the number of both low and high volume. E. Calculating Average Values In order to determine the cost-per-acre for each half-mile section of US Route 28, the buffered US 28 shapefile and the real estate assessment map were imported into ArcMap. First, a new field, Cost, was created in the attribute table of the real estate assessment data. This field was populated using the field calculator and calculated by dividing the sum of the undepreciated value and improvement value by the acreage of the respective parcel. Then, the cost-per-acre features were joined to the 250- foot buffered road to associate the surrounding average value within the vicinity. This process resulted in a shapefile and a database file which include the average cost-per-acre within a 250-foot buffer for each half-mile section. III. RESULTS In order to make decisions about which corridor sections to protect, the transportation planners need to know the correlations among access point density, average priority scores, and values for each half-mile corridor section. As a result, comparisons were made between the number of low volume access points and high volume access points, average priority scores and access points, and average priority scores and value for each half-mile corridor section. Each comparison has a graph associated with it that plots the two variables on the same graph with both variables varying between half-mile corridor sections. Above each graph a map of US 28 was laid on top of the graph to help VDOT visualize where each corridor actually falls along US 28. The map presents US 28 in the actual direction it travels with the left side being the westernmost point and the right side being the easternmost point along the corridor. The different colors represent vulnerability to development for each parcel of land with red representing a high vulnerability and green representing low vulnerability to development. A. Low Volume vs. High Volume Access Points Fig. 3 shows a graph of the total number of access points for each half-mile section along US 28. Each bar is split up between the number of high volume access points and the number low volume access points for each corridor section. Corridor sections with a large number of high volume access points relative to its number of low volume access points indicates a section of US 28 that currently has a lot of development. Corridor sections with a large number of low volume access points relative to its number of high volume access points indicates a section of US 28 that may have a lot of residents but no major development. B. Average Priority Score vs. Access Points Fig. 4 displays a graph that compares the average priority score versus the number of high volume access points. The left-hand axis gives the scale for the average priority score while the right-hand axis gives the scale for the number of high volume access points. Placing these two variables on the same graph shows the places that may have a high vulnerability to development, indicated by the average priority score, and whether or not those corridor sections currently have major development. Sections of US 28 that have a high priority score and a large number of high volume access points may be likely to have future development, but also have a lot of current development that would be costly to alter if VDOT wanted to protect the Fig.3. Profile of US Route 28 with vulnerability to development indicated by color (low: green, high: red) and both low and high volume access points along US

4 Fig. 4. Profile of US Route 28 with priority score indicated by color and comparison of average priority score and number of access points along US corridor. However, sections with a high priority score and a small number of high volume access points are likely to have future development and would not be as costly to protect the corridors from future congestion problems because there is not much current development that would have to be changed or moved. The corridors in this second category are most likely the best places for VDOT to implement corridor protection strategies. C. Average Priority Score vs. Average Value Fig. 5 compares the average priority score versus the value per acre for each corridor section. The left-hand axis gives the scale for the average priority score while the righthand axis gives the scale for the value of each corridor section. Plotting the value of each corridor section alongside the average priority scores shows VDOT which corridor sections have a high vulnerability to development and cost the most or the least. Half-mile sections that have a high priority score and a high value may have a high vulnerability to development, but would cost a lot to protect the corridors. Sections that have a high priority score and a low value have a high vulnerability to future development and would cost less to protect. The corridor sections with high priority score and low value seem to be the half-mile sections that VDOT should target first. IV. DISCUSSION OF RESULTS The results presented above offer a key piece of information to Fauquier transportation planners that is missing from the analysis created by the existing methodology. While his method indicates areas most likely to develop, the management layers created for this project help planners to make decisions about where they can maximize the impact of their investment. While Fig. 2 above helps to identify where the highest densities of access points Fig. 5. Profile of US Route 28 with priority score indicated by color and comparison of average priority score and average value per acre along US

5 are, Fig. 3 indicates how the number of high priority access points aligns with the priority score created by the existing methodology This helps planners to identify areas that are likely to develop but do not yet have many access points making it much easier to implement an access management plan. Examples of such locations occur at milepost 10.5 and Fig. 5 provides similar information. By identifying where land costs are low but priority scores are high, such as at mileposts 5, 10.5, and 13.5 planners can see where they can cheaply acquire right of way and therefore cheaply implement an access management plan. By examining the management layers presented in this project, planners in Fauquier County can see that they can cheaply implement an access management plan at mileposts 10.5 and 13.5, areas that have not yet developed but are likely to do so. [6] Malczewski, J. (2004). GIS-based land-use suitability analysis: a critical overview. Progress in Planning, No. 62, pp 3 65.committee. [7] Plazak, D. (2005). Long-Term Impacts of Access Management on Business and Land Development along Minnesota Interstate 394. Proceedings of the 2005 Mid-Continent Transportation Research Symposium. V. FUTURE WORK There is opportunity to continue work on this project. One way to continue the work is to expand this analysis beyond the case study in Fauquier County presented here to the entire state of Virginia. The methodology will need to be simplified to facilitate rapid analysis. One key step in the methodology was counting the access points along the road. This had to be performed by hand, looking at aerial photos and physically counting the access points. This was time consuming and if a state-wide analysis is to be performed creating a method of automating the counting would be helpful. Another area for future work is in maximizing the informational value of the management layers. This can be accomplished by presenting different informational layers alongside the access point data. ACKNOWLEDGMENTS The authors appreciate the contributions of Chad Tucker, Robin Grier, John Giometti, Rick Tambellini, and others of the Virginia Department of Transportation; Wayne Ferguson and John Miller of the Virginia Transportation Research Council; and Rick Carr of Fauquier County, Virginia; and Jeff Walker of the Rappahannock Rapidan Regional Commission; and other members of a project steering committee. REFERENCES [1] Barnes, G and Watters, S. The Financial Benefits of Early Acquisition of Transportation Right of Way. Minnesota Department of Transportation, [2] Heiner, J. D., and Kockelman, K. M. (2005). Costs of right-of-way acquisition: Methods and models for estimation. Journal of Transportation Engineering, 131(3), p [3] Kamprath, M. T., & Miller, J. S. (2006). Corridor protection through NEPA. Journal of Professional Issues in Engineering Education and Practice, 132(2), [4] Lambert, James and Linthicum, Alexander. (2007). Final Contract Report: Risk-Based Approach to Corridor Protection with GIS Analysis. Unpublished Draft. [5] Linthicum, Alexander. (February 6, 2007). Risk-based Approach to Protecting Accessibility, Mobility, and Safety Options for Transportation Corridors. First report to the project steering