An Investigation Into Tradable Credit Scheme: Accounting For Heterogeneous Users' Travel Choices

Nowadays, traffic congestion has been a serious obstacle to city development.Besides, traffic-generated carbon emissions contribute to a large part in overall greenhouseemissions, which harm the sustainable development of human societies.Tradable credit scheme, a quantity-and-price-combined based policy instrument, is designed to curb traffic congestions and emissions. Compared to congestion or road pricing policy, tradable credit scheme is more acceptable to public in terms of its income neutrality, progressivity, self-financing and etc. Accounting for users'heterogeneity, this research investigates the effect of tradable credit scheme on users'travel choices in single O-D (Origin-Destination) and multipleO-Ds, then explores the system optimal tradable credit design in managing mobility and emission and investigate how to set tiered gasoline pricing accouting for carbon cost. Specifically speaking, the research first gives a literature review on congestion pricing and tradable credit scheme. The literature studies on modeling of tradable credit scheme are elaborated and research gaps are highlighted. And research trails on the system optimal equilibrium are tracked, which lay a basis for the follow-ups. Second, this research focuses on the mixed household and individual travel behaviors under single bottleneck model and investigates how to establish a system optimal tradable credit scheme in managing bottleneck congestion. And then the research extends the single bottleneck model to multi-O-D network and accounts for simultaneous route and departure time choices under tradable credit scheme and on this basis, a bi-level model of road manager and road users is formulated to derive the system optimal credit design in managing congestions and emissions. Based on the market clearing condition of tradable credit scheme, the research proposes the tiered gasoline pricing on the equilibrium credit price and analyses the welfare effect of different user groups under the new pricing mechanism based on the mileage data of 4s shop.Main research details are as follows.First, this research focuses on the effect of tradable credit scheme on mixed users'departure time choices, cost and bottleneck congestion condition under single bottleneck model. It breaks the traditional single bottleneck model which accounts for single household users or individual users and incorporates the mixed travel behaviors of household and individual users altogether in this model. A tradable credit scheme is established to regulate the mixed behaviors and curb bottleneck congestion. This part applies linear complementarity model to build the dynamic user equilibrium and provides the proof of solution existence and other properties. And then PATH solver is used to conduct numerical examples. Results show that in small school-work schedule difference, tradable credit scheme can effectively stimulate behavioral changes and reduce system travel time thus0 alleviating congestion. However, total system travel time increases in large school-work schedule difference, which makes the scheme ineffective. Besides, system travel time keep the same under different initial allocation schemes while household and individual users get Pareto-improvement to different extent.Based on the above, the research further investigates the optimal tradable credit scheme in managing congestion under single bottleneck model. It is proved that total system travel time equals zero, which means that bottleneck congestion is totally eliminated in system optimum. Under this condition, household and individual users depart alternatively, which guarantees zero queue time. Then primal-dual property of linear programming is applied to derive system optimal tradable credit scheme. It is observed that the scheme (K,kt) cannot guarantee the market clearing of credit market. Additional credits should be issued to the credit market to achieve the equilibrium state, i.e. (K, kt,?).Third, this research extends beyond the single bottleneck model to incorporate heterogeneous users' travel behavior in multi-ODs network. It investigates the effect of tradable credit scheme on simultaneous route and departure time choices accounting for travel time cost and emission cost. A mathematical programming with equilibrium conditions is formulated and turned into an equivalent variational inequality problem. And projection algorithm is applied to solve the problem.Numerical examples of three reasonable size networks show that users with lower value of travel time are prone to be more sensitive to tradable credit scheme, while users with high value of travel time are prone to maintain their original travel habits to save travel time. These lay a foundation for the bi-level formulation in next part.Based on the simultaneous dynamic route and path user equilibrium, this part establishes a bi-level model in which road manager in the upper level aims to establish a credit charging scheme to achieve mobility meanwhile alleviate environmental impacts and users in the lower level minimize the travel cost to attain user equilibrium. We propose a projection based pattern search algorithm to solve the bi-level problem. It is observed that in the minimum travel time case, users with high value of travel time and early/late arrival penalty wouldn't choose the path or departure time with lowest credit consumption cost. And in the minimum emission case, all users will choose the path or departure time with the least credit consumption,thus reducing system emissions effectively. Besides, minimum emission travel pattern does not always generate minimum travel time. Similarly, minimum travel time travel pattern does not always generate minimum emissions. An obvious tradeoff between travel time and emissions can be observed under tradable credit design. Road manager can devise an adjustable credit charge mechanism by setting a time-varying weightor between travel time and emissions to achieve both mobility and sustainability in transportation network.Finally, this research proposes a tiered gasoline pricing mechanism based on the equilibrium credit price in tradable credit scheme. Based on mileage data in 4s shops in China, we can derive the first tiered price is 3.89 &/gallon, the second tiered price is 6.44$/gallon and the threshold between the first and second tier is 223.57 gallon.This mechanism is susceptible to the changes in the original gasoline price and emission reduction goal. When the original gasoline price runs high, the authority should raise the first tiered price and lower the second tiered price. When the emission reduction goal becomes stringent, the authority should lower the first tiered price and raise the second tiered price. Moreover. results from the welfare analysis show that users in low income group can get welfare improvement while uses in high income suffer loss, which indicates the progressivity of this pricing mechanism. This part has a significant implication on energy reformation in China.