Analysing the design criteria of charging cordons

The idea of the efficient use of roads, which requires users to pay for the traffic congestion cost that they impose on an urban road network, is long established (Pigou, 1920; Walters, 1961). However, the gap between the constructive theory of road pricing and its real world application is significant due to the issue of public acceptance, technical feasibility, and the cost of implementation (Sharp, 1966; Verhoef et al, 1995; Stenman and Sterner, 1998; and Sumalee, 2000). Different charging regimes have been developed and studied including time or delay based charging, distance based charging, cordon or boundary based charging, and area based charging (Holland and Watson, 1978; May, 1992; Oldridge, 1990; Smith et al, 1994; and Ison, 1998). The cordon charging system is the core of the study in this paper where we are looking for criteria for the judgmental design of cordons. We use the term “judgmental cordon design” to describe the process to identify the best locations to levy the charges and specify the optimal charge levels based on professional judgment. This paper reviews the literature to identify design criteria in section 2, and then it describes a survey with six UK local authorities in section 3. Section 4 presents the results of the survey and finally section 5 discuss the results and draw the conclusions

Link-based multi-class hazmat routing-scheduling problem : a multiple demon approach

This paper addresses a hazmat routing and scheduling problem for a general transportation network with multiple hazmat classes when incident probabilities are unknown or inaccurate. A multi-demon formulation is proposed for this purpose. This formulation is link-based (i.e., the decision variables are link flows) and can be transformed into other forms so that a wide range of solution methods can be used to obtain solutions. This paper also proposes a solution strategy to obtain route flow solutions without relying on exhaustive route enumeration and route generation heuristics. Examples are set up to illustrate the problem properties, the method of obtaining route flows from link flows, and the computational efficiency of the solution strategy. Moreover, a case study is used to illustrate our methodology for real-life hazmat shipment problems. From this case study, we obtain four key insights. First, to have the safest shipment of one type of hazmat, different trucks carrying the same type of hazmat need to take different routes and links. Second, in case of multiple-hazmat transportation, it is recommended to use different routes and links for the shipment of different hazmat types. This may increase travel time but can result in safer shipment. Third, if the degree of connectivity in a transportation network is high, the shipment company may have multiple solutions. Fourth, the hazmat flows on critical links (whose removal would make the network disconnected) must be distributed or scheduled over different periods to have safer shipment

Sensitivity analysis of the variable demand probit stochastic user equilibrium with multiple user classes

This paper presents a formulation of the multiple user class, variable demand, probit stochastic user equilibrium model. Sufficient conditions are stated for differentiability of the equilibrium flows of this model. This justifies the derivation of sensitivity expressions for the equilibrium flows, which are presented in a format that can be implemented in commercially available software. A numerical example verifies the sensitivity expressions, and that this formulation is applicable to large networks

Second best toll and capacity optimisation in network: solution algorithm and policy implications

This paper looks at the first and second-best jointly optimal toll and road capacity investment problems from both policy and technical oriented perspectives. On the technical side, the paper investigates the applicability of the constraint cutting algorithm for solving the second-best problem under elastic demand which is formulated as a bilevel programming problem. The approach is shown to perform well despite several problems encountered by our previous work in Shepherd and Sumalee (2004). The paper then applies the algorithm to a small sized network to investigate the policy implications of the first and second-best cases. This policy analysis demonstrates that the joint first best structure is to invest in the most direct routes while reducing capacities elsewhere. Whilst unrealistic this acts as a useful benchmark. The results also show that certain second best policies can achieve a high proportion of the first best benefits while in general generating a revenue surplus. We also show that unless costs of capacity are known to be low then second best tolls will be affected and so should be analysed in conjunction with investments in the network

Optimal road pricing scheme design

There are two main approaches to designing road pricing schemes. The first is judgmental in nature and focuses on the acceptability and practicality of the scheme. The second is based on theory concentrating on the optimality and performance of the scheme. This research aimed to integrate these two approaches into a single framework and to develop a tool to aid the decision maker in designing a practical and optimal road pricing scheme. A review of the practical design criteria and a survey with six local authorities in the U. K. were conducted to clarify the concept of the judgmental design. A simple charging scheme like a charging cordon is believed to be the most practical charging regime due to its simple structure. The decision on the boundary and structure of the cordon is based largely on public acceptability and possible adverse impacts. Road pricing is used to serve several objectives including congestion reduction, revenue generation, and increase in efficiency of the transport system. The framework for the theoretical optimal toll design problem adopted was a Stackelberg game where the travellers' behaviour were assumed to follow the concept of Wardrop's user equilibrium. This problem can also be formed as a Mathematical Program with Equilibrium Constraint (MPEC). After reviewing various methods for solving the MPEC problem, three possible methods (the merit function method, improved cutting plane algorithm, and Genetics Algorithm (GA) based algorithm) were developed and tested with the optimal toll problem. The GA based algorithm was found to be the most appropriate for the development of the design algorithm with practical constraints. Three different features of the judgmental design were included into the optimisation algorithm: the closed cordon formation, constraints on the outcomes of the scheme, and the allowance for multiple objectives. An algorithm was developed to find the optimal cordon with an optimal uniform toll. It is also capable of designing a scheme with multiple cordons. The algorithms for solving the constrained optimal cordon design problem and the multiobjective cordon design problem were also developed. The algorithm developed for the multiobjective problem allows the application of the posterior and progressive preference articulation approach by generating the set of non-dominated solutions. The algorithms were tested with a network of Edinburgh. The results revealed several policy implications. Adopting a judgmental cordon with a simple uniform toll may be less effective. A variable optimised toll around the judgmental cordon can generate around 70% more benefit than the optimal uniform toll. The optimised location of a cordon generated about 80% higher benefit compared to the best judgmental cordon. Additional constraints such as a maximum of total travel time decreased the level of the benefit of the scheme by 90%. Different objectives may require different designs for the charging cordon scheme. The welfare maximisation cordon should focus on those trips contributing most to the social welfare function which are mainly in the congested areas with an appropriate toll level. The revenue maximisation cordon should impose a higher number of crossing points and minimise possible diversion routes to avoid the tolls which should be high. The equity cordon should cover a wider area of the network with low toll level to ensure a good distribution of the cost and benefit to all origin-destination pairs. The algorithms developed can offer support to the decision maker in developing a charging cordon scheme by formalising the process of charging cordon design. This will increase the transferability of the technique and the transparency of the decision process

Travel time reliability-based optimization problem for CAVs dedicated lanes

This paper proposed an optimization problem that determines the deployment pattern of dedicated lanes to connected autonomous vehicles (CAVs) considering the stochastic traffic demand and the stochastic traffic capacity. The difference between CAVs and regular human-piloted vehicles (RHVs) is driving behavior. The driving behavior of CAVs is expected to be more standardized than that of RHVs. Therefore, we assume that when the penetration ratio of CAVs increases in the lane flow, the mean lane capacity will increase, and the lane capacity variance will decrease. The mean and the variance of lane travel time decrease when the penetration ratio increases. Following this assumption, the difference in the stochastic properties between CAVs and RHVs is considered in a traffic assignment model. The traffic assignment model is formulated as a variational inequality problem. The network design problem with equilibrium constraints was solved by a simulated annealing algorithm in a test network

Evaluation and enhancement of transport network reliability: Network equilibrium based approach

Department of Civil and Environmental Engineerin