A transportation network assessment tool for hazardous material cargo routing

hazardous material transportation (advances in engineering)

Significance Statement

A new study by Inanloo and Tansel from the Civil and Environmental Engineering Department at Florida International University in Miami proposed a new framework in evaluating the transportation networks in regards to their suitability for shipments of hazardous material. Their results appear in Journal of Loss Prevention in Process Industries.

Substantial research on designing road networks for hazardous material focused mainly on travel cost through link length and in some cases risks taken in account for network assessment or design has been reported in the past. However, travel cost which is the most important criterion in transportation of hazardous materials also poses major concerns in terms of accidental release in densely populated areas during lowest cost route and exposure of hazardous materials during congestions and traffic delays causing major health risk to people.

The tool developed by this study is flexible for conducting comparative assessment of routing options for a given study area which is written in Python program capable of analyzing, evaluating and calculating transportation network by one time execution program obtained in maps and tables.

The four criteria considered in development of the network assessment tool includes; impacts of exposure to accidental release, proximity to vulnerable areas, delay costs and freight expenses. Health risks in exposure to accidental releases are a measure of probability and severity of threats to a receptor. AEGL-3 which represents concentration of harmful substance in ppm or mg/m3 was taken into account as threshold concentration for health impact radius. The number of exposed people found in the impact radius is subject to health risks due to inhalation of hazardous chemicals which are dependent on accident frequencies and consequence analysis.

An accident frequency according to Highway Safety Manual (HSM) is the calculation of crash frequencies or degrees to which a road user is exposed to traffic rules. Consequence analysis of health impact buffer zones around the road was achieved by finding the farthest distance the concentration could be perceived using Gaussian Dispersion Equation written in Python programming language which runs the calculations for the study area by calling the spatial data from GIS maps. Concentrations were calculated for downward direction without any deviation from centerline of wind and ground level. Standard deviation calculation depends on stability of atmosphere which corresponds to the ability of air molecules in creating vertical movements. The faster the movement, the quicker the dilution of substance in the atmosphere hence, less health impacts can be expected. The stability of class of atmosphere is a function of wind speed, solar radiation and cloud cover. The health impact radius was used as a buffer distance around spill location towards any direction disregarding any orientation of wind which is based on assumption Gaussian Dispersion Equation that particles disperse by power of wind towards downward direction. Delay cost should not also be undermined as congestion or traffic delays causes an additional time of travel resulting to higher consumption of fuel. Delay cost is estimated by multiplying the delay time caused by an accident to dollar value of travel time delay. Queuing analysis used in estimating delay time identifies other criteria such as number of lanes, speed limit and function class of road segment to calculate road capacity.

Estimation of freight transport cost is also needed in order to minimize total cost of conveyance for competitiveness and excellent delivery of goods. It was estimated by multiplying the average total carrier cost with the travel distance for each route. The tool developed by this study also considers vulnerable places such as schools, daycares, hospitals etc. for evaluation of transports. These vulnerable places have huge number of patients and children who are prone to health risks when exposed.

This case study was done in city of Miami in Florida, USA in order to implicate the tool on a real world problem. In assumption to worst case scenario, the whole cargo was presumed to be released by accident. Toluene as a hazardous substance present in gasoline was taken into consideration and analysis was focused on assessing the exposure impact radius by inhalation after accidental release. Output results such as data, analysis and calculations were executed by Python and visualized with the aid of ArcGIS. It was seen that the buffer distances are different according to atmosphere stability as it plays a significant role in delusion of chemicals in the air.

Also, in the study, numbers of vulnerable points which fall into health risks zones of each segment were assigned to the segment of transportation network. This same meteorological data showed results of road capacity before and after accidents for each segment as delay time was computed for each of the network branch. Delay cost was found by multiplying the capacities of cost after accident and cost per hour of delay in the area of occupancy rate as visualized.

The results of this study would go a long way in aiding decision makers on optimization of routes for efficient transport of hazardous material. 

CITATION: Bahareh Inanloo, Berrin Tansel. A transportation network assessment tool for hazardous material cargo routing: Weighing exposure health risks, proximity to vulnerable areas, delay costs and trucking expenses. Journal of Loss Prevention in the Process Industries, Volume 40, 2016, Pages 266–276.

Affiliation: Civil and Environmental Engineering Department, Florida International University, 10555 West Flagler Street, Engineering Center, Miami, FL 33174, USA.

 

Go To Journal of Loss Prevention in the Process Industries

 

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