Risks associated with the transport of hazardous materials (hazmat) by truck and rail are viewed from two perspectives: society in general and the individual residing adjacent to the route. Societal and individual risks are assessed for the bulk transport of liquefied chlorine gas along a typical highway/rail corridor. The results of this analysis suggest that individual risks associated with the bulk transport of chlorine gas by truck and rail are low, and in the acceptable range. Significant differences in individual risks were observed between the two modes. Societal risks are much more significant than individual risks, given their concern with very low frequency—high consequence events. For the bulk transport of chlorine along the selected corridor, societal risks for trucks are moderately higher than for rail. Consideration of both individual and societal risks renders the risk analysis process more complete for the purpose of decision‐making.

To conduct risk assessments in routing studies for the highway transportation of hazardous materials (hazmat), estimates of accident and release rates are essential. Published literature underscores the importance of these rates in risk assessment, and the significant shortcomings of the available data. Truck accident rates are developed in this paper as a function of roadway type and area type (urban/rural) from state data on highway geometrics, traffic volume, and accidents. Release probabilities in accidents are derived from a combination of federal and state truck accident data bases. The procedure is presented in detail. A discussion of the dangers of combining data from different states is also presented, along with justification for the decision of the writers to do so. A revised model for the accident probability portion of the U.S. Department of Transportation (DOT) hazardous materials routing guidelines is recommended. Statistical tests are presented to determine whether accident rates based on site‐specific data or systemwide values, such as those derived in this paper, should be used for any particular route segment.

To assess the best routes for the transport of dangerous goods in an area of 600 km² in France, software based on a geographical information system was developed to manage, treat, and represent statistical and geographical data related to the evaluation of the risk of transport on a road network. The probability of an accident and release is derived from the links in a digitized network, provided by the Institut Géographique National (IGN) on a 1/50,000 scale, according to the links' characteristics. The active, student and nonactive population figures are from the 1982 census, and are distributed among categorized (i.e., urban, industrial) areas of administrative units called communes. The intersection of this population layout with an impact zone leads to a measure of the people exposed to damage. An impact zone is a corridor along a road; the diameter of the zone depends upon the nature and quantity of dangerous materials that are being transported. Multiplication of the accident probability by the number of people exposed gives an estimation of the relative risk, which is used to compare alternative routes so that the least risky route is chosen.

Kansas State University (KSU) conducted a comprehensive study of the development of a set of prioritized, extreme‐risk scenarios; the development of a set of feasible, practical, and implementable protective systems, and a report to summarize guidelines on the use of these protective systems to mitigate potential, extreme‐risk situations that could occur during the transport of hazardous materials (hazmat) on our highway system. The present paper covers the methodology used to apply the Delphi technique with a state's panel to complete the first two objectives; and, in addition, an initial evaluation of the effectiveness of these protective systems. The research study was limited to materials spilled within the highway system. It focused on potential risks that would result in severe, long‐term, permanent, irreparable, or catastrophic consequences, and existing technology and state‐of‐the‐art knowledge for development of protective systems to mitigate these consequences. The protective systems within the scope of this study were systems constructed or physically incorporated into the highway system or modifications thereto.

Pennsylvania has accounted for the highest number of hazardous material incidents in the United States between 1971 and 1983, with 90% of the incidents being highway related. The Pennsylvania Department of Transportation has sponsored a research project that focuses on the risk assessment associated with the movement of hazardous materials and determination of corresponding vulnerable areas in the state. The risk assessment of hazardous‐material movements is data intensive, and its analysis depends on several data sources and on the quality of the input data. Three data bases are analyzed for this project: (1) The Research and Special Programs Administration (RSPA) hazardous material incident reports (HMIR); (2) the Bureau of Motor Carrier Safety (BMCS) truck accident data base; and (3) the Pennsylvania State traffic accident data base for hazardous material. In addition to the individual analysis, a comparison among these data bases was also made. The comparison was conducted to find out whether the characteristics of accidents and incidents are consistent in different data bases.

With geographic information systems for transportation (GISTs) gaining wider acceptance by government agencies, attention is turning to the application of this information technology to sophisticated transportation management problems, often requiring real‐time decision making. Two areas of priority concern that many agencies have identified are the management of highway incidents and transportation hazard analysis. Incident management considerations include those of emergency response deployment and rerouting to bypass the affected area. Transportation hazard analysis also addresses dynamic routing and emergency preparedness in the case of a hazardous‐materials transport release, and involves comprehensive risk assessment and evacuation planning. The objective of this paper is to describe methods employing GIST that can provide the capability to perform transportation hazard analysis and incident management. These methods are subsequently applied in several case studies involving highway operations in California to illustrate their implementation. The paper concludes with a discussion of how the GIST approach to incident management may be extended to address dynamic management in an intelligent‐vehicle‐highway‐system environment.

The current method of computing the intergreen (yellow plus all‐red) interval at signalized intersections assumes that the component variables are deterministic. This paper presents a probabilistic method in which the approach speed, reaction time, deceleration rate, and vehicle length are random variables. The intergreen interval is estimated so that the dilemma zone occurs with a specified probability. A safety margin is defined as the difference between the clearing and stopping distances, which are random variables. Relationships for the mean and standard deviation of the safety margin are developed based on the first‐order second‐moment analysis. A closed‐form solution of the intergreen interval is then derived. The safety margin is assumed to be normal, and this assumption is confirmed. The probabilistic method should be valuable in designing the intergreen interval for any desired reliability level.

The maximum permitted length of trucks on Canadian roads has increased significantly over the past 20 years. This has led to concern regarding the interaction of trucks with other elements in the traffic stream. This paper presents a summary of the effect of increased vehicle length on passing operations and, specifically, it looks at the effect on passing‐sight‐distance requirements of increasing the overall maximum vehicle lengths from 23 m to 25 m. Passing‐sight‐distance requirements were calculated based on generalized versions of models developed by Lieberman, in 1982, and Glennon, in 1988. The inherent random nature of vehicle and driver characteristics were incorporated into the passing model by conducting a discrete stochastic simulation of the passing maneuver. The results of the modeling exercise indicate that passing‐sight distances are considerably greater when passing a long truck than when passing a car. However, whether the truck is 23 m or 25 m long does not have a significant impact on the passing‐sight‐distance requirements.

Recently, the use of preformed membrane systems has increased as a corrosion preventive technique in reducing chloride intrusion into reinforced concrete bridge decks. However, there is no nondestructive method to evaluate the integrity of in‐place preformed membranes. Also, the effectiveness of preformed membranes was not sufficiently addressed. Three different nondestructive methods are evaluated to investigate the integrity of preformed membranes. Ultrasonic pulse velocity is found to be the most feasible. The effectiveness of preformed membranes is investigated by collecting concrete powder samples from bridge decks protected by preformed membranes at three depths. A field evaluation of the preformed membranes' performance is conducted on fifteen bridge decks in three states: New Hampshire, Maine, and Vermont. The membranes were installed on the decks when new. The bridges' ages are varied from 2 to 32 years old. They are exposed to different average annual daily traffic, salt application rate, snowfall, and so forth. Approximately 45 nondestructive tests were carried out, an average of 14 ground truth cores were obtained, and at least 45 concrete powder samples were analyzed for chloride content per bridge deck. The field evaluation concluded that preformed membranes reduce chloride intrusion if they are installed properly and overlaid with an appropriate layer of hot‐mix asphalt, which should be kept in a good service condition. An average life of 40 years is expected for preformed membranes, and an increase of 25 years in bridge deck life is expected.

The trends in Canadian domestic air‐travel demand during the past 20 years are described, and the annual changes in domestic air demand are shown to relate only very generally to the annual changes in economic activity. The longer term trend suggests that the domestic air‐travel market has matured and the efficiencies obtained from the technological advances introduced in the early 1970s have been absorbed by the market. Air‐travel demand grew at a faster rate than economic activity before 1983 but has lagged economic growth since 1983. This change is related to the sharp downturn in per capita expenditures on domestic air travel during the recession in the early 1980s and the fact that these earlier expenditure levels have not returned. Attempts to model the Canadian domestic market by both aggregate and disaggregate models are described and it is pointed out that these models have very marginal contributions to make to intercity transport public policy formulation and analysis in Canada. The paper also points out the fundamental air travel interaction structure between the major market areas in Canada has changed very little over the past 20 years and that simple updates of the existing demand structure using Fratar‐type expansions of existing travel patterns appear to be the only justifiable approach.