Trial and error method for optimal tradable credit schemes: The network case

Abstract

Recent studies on the new congestion reduction method-tradable credit scheme rely on the full information of speed-flow relationship, demand function, and generalized cost. As analytical travel demand, functions are difficult to establish in practice. This paper develops a trial and error method for selecting optimal credit schemes for general networks in the absence of demand functions. After each trial of tradable credit scheme, the credit charging scheme and total amount of credits to be distributed are updated by both observed link flows at traffic equilibrium and revealed credit price at market equilibrium. The updating strategy is based on the method of successive averages and its convergence is established theoretically. Our numerical experiments demonstrate that the method of successive averages based trial and error method for tradable credit schemes has a lower convergence speed in comparison with its counterpart for congestion pricing and could be enhanced by exploring more efficient methods that make full use of credit price information.We note that such a tradable credit scheme will cause inconvenience to non-local residents who want to enter or go through the city, because they need to purchase credits from the local credit trading market, and buy or rent in-car equipment for credit payment before entering the city. However, such inconvenience for non-local residents exists not solely under tradable credit schemes. In Singapore where congestion pricing is implemented, the non-local residents also have to purchase in-car equipment for road pricing from convenience stores near the city edge before entering the city. With fast development of technology, we believe such inconvenience is minor. Furthermore, if desired, the social planner could let non-local users pay traditional congestion charge instead when entering a city or region. Indeed, differentiated treatment of local and non-local traffic is underway in Beijing for its traffic rationing scheme (similarly in Shanghai). It is also politically justifiable because it is the local taxpayers' money that has been used for road construction and maintenance. 686 X. WANG ET AL.As proved by Yang and Wang [1], the UE link flowv and demandd under any credit scheme (K,κ) are unique, and the ME credit pricep is unique as long as there exists at least one O-D pair w ∈ W 688 X. WANG ET AL.

Tradable Credit Schemes in Managing Network Mobility: Brief Review and New Developments

“…Later, Wang et al (2013) further extended the trial-and-error procedure for implementation of tradable credit schemes in general networks. The procedure updates tradable credit schemes from observed link flows and credit prices, based on the successive average method.…”

Investigating the Impacts of Transaction Cost under a Tradable Credit Scheme with Heterogenous Users

“…In the context of TCS, Wang and Yang [40] proposed a trial-and-error implementation of the tradable credit schemes for a single road. Later, the authors extended it to a general network case [41]. Different from the two existing works, which focus on solving equilibrium travel demand and optimal credit charge pattern, respectively, we propose a trial-and-error method for solving the equilibrium credit price in this paper.…”

Investigating a tradable credit scheme with the system optimum theory

“…''u = 1-16'' is the O-D pair in the network (Figure 1). The standard US Highway Bureau impedance function is employed as the link impedance function, 18,36 namely t i (F i ) = t 0 i ½1 + 0:15(F i =c i ) 4 . The relevant parameters of each link are shown in Table 1.…”