| Because the hazmat have flammable, explosive, poisonous, erosive and other physics and chemistry characteristics, once vehicles carrying these materials take place fire, explosion and other accidents in the transportation process, not only will bring irretrievable damage towards the resident and property, but also will have possibility to cause serious ecological environment pollution. Therefore, how to guarantee hazmat transportation safety and reduce accident risk has vital practical significance to safeguard the people's personal and property safety and social stability. The reality shows that the route optimization for hazmat transport is one of most effectively measures to reduce transportation risk. But now, the researchs concerning risk analysis and route optimization for road hazmat transport in domestic and foreign still have many weak points. So, this paper begins from the statistic analysis of typical accidents cases, and based on establishing multi-dimension risk assessment model for the road hazmat transport, carries out the research on the multiobjective route optimization of hazmat transport in a deep-going way, the main research aspectsare as follows:①comprehensively reviews the literatures relating the risk assessment and route optimization for the road hazmat transport. Through carrying out the statistical analysis on typical accidents cases of hazmat transport, the characteristics and rules of accidents, including accident pattern, time, and road section and so on are investigated, and then "5M" influencing factors for the road hazmat transport risk is determined. According with the problems that existing in the over-mentioned factors, several risk reduction measures for the road hazmat transportation are proposed, which are suitable for China's situation.②constructs a multi-dimension risk assessment model for the road hazmat transport from the probability and severity of accident. Among the accident probability model, the basic release probability based on route area, road type and the class of hazmat (involving release probability caused by traffic accidents and by non-traffic accidents) is not only put forwarded, but also the accident probability modification coefficient is introduced to revise the above-mentioned basic probability. Subsequently, the computation method of the time-varying accident probability is proposed. Among the accident consequence severity model, a quantitative calculation method for the en-route and off-route exposed population as well as the exposed environmentally sensitive area in the impact area is put forwarded, and then the time-varying road hazmat transport risk and accident consequence severity is determined by using the proportion of resident trip and the traffic flow variation coefficient.③study on the problem related to multiobjective route optimization for the road hazmat transportation for a given origin and destination under the static condition. Based on establish a mathematical model for the over-mentioned problem, the grey relation analysis method is applied to identify the most satisfied route in all nondominated routes for overcoming subjective factors influence in traditional model.④study on the problem related to the multi-objective rout optimization for the road hazmat transportation for multiple pairs of origin and destination under the static condition. Aimed at two-level restraints in the over-mentioned problem, that is the government designates a subset of the transport network for hazmat transport and carriers select routes on this subset, and given attention to the different benefit targets between government and carriers, a bilevel network flow model for above-mentioned problem is delivered. At same times, a heuristic algorithm that always finds a stable solution for the bilevel model is proposed.⑤discusses the problem related to multi-objective route optimization for the road hazmat transport with time windows constraints and time-varying attributes and for a given pair of origin and destination. Based on establish a mathmatical model which can identify all nondominated time-varying routes with multiple departure time at the origin and waiting time at intermediate nodes along these paths for a given pair of origin and destination, subject to three kinds of practical constraints: limited operational time period, and service, and waiting time window constraints at a node, the proposed model is equivalently transformed into a static multiobjective shortest path problem in an acyclic network reconstructed by the space-time network technique, and an efficient dynamic programming method is then developed.⑥finally, a transport task of the liquified petroleum gas carried out by a transport enterprise of Shaanxi province is taken as an example. On the one hand, the accident probability of LPG transport as well as the exposed risk concerning the en-route and off-route population and the environmentical sensitive area is computed by applying the proposed risk assessment model. On the other hand, by adopting the proposed route optimization model, the most satified LPG transport route with definite departure time at the origin is determined, subject to three optimization objectives: the minimum transportation risk, time (or distance) and cost. The example shows that the proposed risk assessment for the hazmat transport can more accurately reflect the risk level of each road section in actual transport process, and the established route optimization model and algorithm have better operability in solving such complexity problem, which can provide technical support to decision-making of the government authorities and enterprises of the road hazmat transport.
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