GIS to Minimize the Impacts of Hazardous Waste Shipments

This paper presents the use of GIS in the Birmingham, Alabama, metropolitan area to reduce the potential impact of hazardous waste transport shipment incidents. The assessment focuses on determining the optimal route for shipments that minimizes both the travel distance of the shipment and the population exposure along the route. The project developed a case study that compared school locations, number and mobility of students in the school, and the distance between school and hazardous waste route. The results demonstrate that GIS can develop a route that minimizes the impact of hazardous waste incidenst occurring along the roadway network.

Introduction

In the U.S. there are over 500,000 shipments of hazardous materials made every day (1). More than 90 percent of these shipments are transported via truck on the nation’s highways. At any given time, 5 to 15 percent of the trucks on the road are carrying hazardous materials regulated under the Hazardous Materials Transportation Act of 1975 (HMTA). Almost 50 percent of these materials are gasoline and other corrosive or flammable petroleum products, and 13 percent are chemicals. The remaining shipments represent any of the 2,700 chemicals considered hazardous when transported in interstate commerce. Because of the amount and difficulty associated with handling an incident involving one of these hazardous chemicals, citizens and governmental agencies have become increasingly concerned about the risks of transporting these materials.

In an attempt to increase public safety during hazardous waste shipments, this research develops a low-cost, portable, easy-to-use, hazardous waste transport system (HWTS) to identify routes that minimize potential impacts of incidents resulting in the possible spill of hazardous materials from the point source origin to destination (landfills, waste-to-energy, recycling plants or reprocessing plants).

The HWTS is a PC-based application program utilizing a geographic information system (GIS) to identify travel routes for the transport of hazardous materials. ArcView GIS software is used to store roadway data and other socio-economic location in a level-one GIS for Alabama identifying sensitive locations as well as develop the safest route. The routing analysis is capable of using a combination of roadway length, population density and proximity to sensitive area within the state such as schools, daycares, nursing homes, and hospitals. In addition, the HWTS is designed to select the safest route for transporting hazardous materials with different impact characteristics.

The paper presents the design and application of the HWTS conceptual model, a case study documenting the applicability of the model, and concludes the system can generate routes, which reduce the impact of potential incidents without requiring excessive transportation distances and travel times.

HWTS Methodology

The methodology for the Hazardous Waste Transport System (HWTS) uses a common shortest path algorithm in conjunction with a modified highway system. The shortest path algorithm operates as any standard mechanism to perform typical routing, such as Dykstra’s Algorithm or Moore’s Algorithm (2). The modification to the methodology is developed from the network travel characteristics. Traditionally, the shortest path is based on travel time for the roadways in the network. In this methodology, the travel times for the roadways are modified by a constant pursuit to define the roadways in terms of a safety criteria, then the shortest path through the network is essentially becomes the safest path through the network attempting to balance the length of time on the network roads with the impact of a hazardous waste shipment incident.

The modifications of the roadway travel times are developed using the vulnerability of the facilities that lie along each segment of the route corridor. This is calculated as a relationship between the population of the facility and its distance from the road segment. For example, using schools as the vulnerable facility, the population of the school represents the potentially affected population. The relative risk associated with the facility is lowered as the distance from the road increases and it become higher with increasing population of the facility. From this, it is obvious that:

Population µ Vulnerability,

and

Distance µ 1/Vulnerability.

The relative reciprocal function that is recommended as:

f(p,d) = p / (250 d) [1]

Where, p is the population of the facility, d is the distance from the road link to the facility, and 1/250 is a recommended risk constant.

The total vulnerability, which can be assumed for graphic purposes as the radius of the circle around that facility on the route segment, is calculated using equation [1] by adding up the values (radii) of all the facilities lying in the route corridor. The expression can be written as:

Impact = sum ( f ( p,d ) [2]

Case Study: Birmingham, AL.

The case study examined in this research was a hazardous waste routing across Birmingham, Alabama. The goal is to route a hazardous product from an origin location to destination while minimizing the impact of the shipment. As identified in the methodology, there are many features of interest to avoid when routing hazardous material, however, for the case study; we will address only schools located within the county.

To begin, our necessary data is gathered into the GIS. The roadways for Birmingham, Alabama (Jefferson County) are form the 1995 TIGER files. The point locations for schools are taken from a directory of Jefferson County Schools and show differences in type of school, elementary, junior high, and high school (shown in Figure 1).

Figure 1. School Locations in Birmingham, AL.

After collecting the necessary data, the HWTS asks for the user to specify the locations for the shipment origin and destination. The user provides this information by selecting the appropriate locations on the map. For the case study, this is shown and labeled in Figure 2.

Figure 2. Waste Origin and Destination.

With no regard for reducing the impact of the hazardous waste shipment in the community, the carrier would move the shipment on the shortest possible path between origin and destination. For this particular example, the path is 10.54 miles across town (see Figure 3). Examining the route we see that there are nine elementary schools, two junior high schools, and two high schools located within one half mile of the route. Should an incident occur with this hazardous waste movement, this route places several school-aged children at risk of being exposed to harmful elements.

Figure 3. Shortest Path through the Network.

Using the location of the Jefferson County schools and the roadway adjustment methodology presented in the previous section, the HWTS will be used to develop a new route that minimizes the potential impact on area schools. GIS is used in the HWTS to provide additional values for roadway segments falling within specified distances of area schools. These values are then included with the roadway segment distance, to develop a new potential impact distance for the roadway segment. For the case study example, the student population of each elementary school is input as 200, each junior high school as 500, and each high school as 2,000. The ring around each school shows the hazardous waste routing impact zone and each roadway segment the falls into this zone of influence is assigned a hazardous waste impact value based on proximity to the school (shown in Figure 4).

Figure 4. School Zones of Influence.

The shortest route compared to the school zones of influence show that there are significant areas where this route passes close to schools (see Figure 5).

Figure 5. Schools Impacted by Shortest Route.

Using the combined roadway distance and impact score, a new route is developed that minimizes potential impact associated with a hazardous waste shipment. The new route is shown in Figure 6.

Figure 6. Safest Route through the Network.

Examining the two routes, the shortest path route has a distance of 10.54 miles compared to the minimized impact route of 11.68 miles. However, with the combined distance and impact score, the route that initially had the shortest path is scored as 38.91 and the route that minimizes potential impact is scored as 32.40. Thus, providing a transport route for a hazardous waste shipment that reduces the potential impact of an incident.

Conclusions

This paper presented the development of a geographic information system based hazardous waste transport system (HWTS) that is intended to reduce the impact of potential incidents regarding hazardous waste shipments across an urban area. The methodology included in the HWTS provides for the determination of transportation routes that attempt to minimize the impact of potential incidents by incorporating socio-economic considerations into the routing process. The case study shown for Birmingham, Alabama is provided to demonstrate the use of the HWTS using school locations as the socio-economic consideration. As demonstrated in the case study, the shortest route for the shipment, only 10.54 miles, passes by several city of Birmingham and Jefferson County schools. When the location of each school is considered into the routing equation, there is a small increase in total distance of travel, however, there is a larger increase in potential safety associated with the longer route.

This research can be extended to include all pertinent socio-economic characteristics desired by the community. Some additional vulnerable facilities might include daycares, hospitals, and retirement communities. In addition, police stations, fire stations, and emergency response units might be used as locations that provide a benefit for controlling response and protecting the general population. Another extension would be the development of a matrix of information containing parameters and vulnerability function for different hazardous waste shipments. This would allow the HWTS to provide optimal routings for different shipment properties (liquid versus gas, corrosive versus toxic).

References

1. Hazardous Materials Transportation Uniform Safety Act of 1990. P.L. 101-615, 104 Stat. 3244, codified at 49 U.S.C.App. 1801, et seq.

2. Ortuzar, J.D. and L.G. Willumsen. Modelling Transport, 2nd Edition. Wiley and Sons, NY, NY. 1999.

Author Information

Dr. Michael Anderson, Assistant Professor of Civil Engineering, Department of Civil and Environmental Engineering, The University of Alabama in Huntsville, Huntsville, AL 35899, (256) 824-5028, (256) 824-6724, mikea@cee.uah.edu

Dr. Robert Pitt, Professor of Civil and Environmental Engineering, Hoehn Engineering Bldg., 1075 So. 13th St., University of Alabama at Birmingham, Birmingham, AL 35294-4440, (205) 934-8434, rpitt@eng.uab.edu

Samina Panwhar, Staff Engineer, LFR, Levine Fricke, Emeryville, CA, (510) 595-7354, samina.panwhar@lfr.com.