  A wide range of price-based congestion management schemes were proposed in
the literature ranging from marginal cost road pricing to trip based multimodal
pricing. The underlying models were formulated under different theoretical
assumptions and with varying, and sometimes conflicting objectives. This paper
presents a unifying framework under which different approaches can be compared
based on their respective assumptions. The unifying modelling framework is
referred to as trip pricing model, which extends path-differentiated pricing to
multimodal paths, i.e., trips on whatever mode or combinations of modes, and
generalizes road pricing schemes (which are shown to be a special case). By
setting both positive (tolls) and negative (incentives) prices, revenue-neutral
schemes are also shown to be special cases, with no a-priori assumption on
which paths/modes to toll/incentivize. For model comparison, the pricing design
problem is formulated in a multi-objective optimization framework, which
combines traffic efficiency, environmental sustainability, users' acceptance,
social and spatial equity, as pricing objectives. The trip pricing scheme is
compared with traditional road pricing schemes, and with their revenue-neutral
variants. First-best and second-best pricing schemes, designed in single- and
multi-objective optimization frameworks, are compared on the Nguyen-Dupuis
network. Results suggest a vast potential for multi-objective trip congestion
pricing over single-objective road pricing. In addition, the application of
both positive and negative prices is shown to significantly increase the
expected acceptance of pricing schemes and to preserve efficiency and
sustainability objectives. The results should promote the design of more
effective pricing policies, i.e., set of pricing rules easier to communicate,
based on now available technologies of passengers' tracking and pricing.
