This paper examines the distinctions and similarities between passenger and freight transportation planning models. It outlines the structural differences between the two systems — including decision-making autonomy, infrastructure requirements, and supply network complexity — and explains how these differences shape model design. The paper discusses how passenger models focus on individual travelers and homogenous groups, while freight models must capture complex multi-actor interactions and origin-destination pair outputs. It also identifies shared characteristics, noting that both systems use the same physical network, which allows modified passenger models to inform freight model development. Key modeling software and output metrics for both system types are highlighted throughout.
Transportation is a fundamental component of modern society, capable of yielding massive economic and social benefits while also producing extremely costly negative externalities. Proper policies need to be put in place to minimize those externalities while taking full advantage of the benefits. Such policies can only be devised through the use of appropriate and well-considered transportation models.
Freight and passenger transport systems usually move through separate nodes, which implies that their structures are quite different from each other — and so are the designs of their respective models. The differences are most pronounced at the respective terminals, which often involve different locations and different facilities. The rationale behind the operational differences between freight and passenger transportation systems is that whereas "each passenger is an independent decision-making unit, each load of freight must be managed from its origin to its destination."
Other significant differences between freight and passenger transportation systems that ought to be taken into account when developing transportation models include the following:
First, freight is 100% passive in nature and typically requires specific loading and unloading infrastructure. Second, most freight vehicles are designed specifically for the shipment of a particular type of goods. Third, freight transport ranges from the shipment of single parcels to that of bulk items weighing thousands of tonnes. Fourth, unlike passenger transport — where decision-making is largely independent — a freight transport itinerary is influenced by several actors, including the driver, freight-forwarder, carrier, consignor, and consignee. Fifth, in the freight transport market, transport shipment and service frequency costs often remain undefined until a prospective "sender makes an inquiry" (Friedrich, Haupt & Nokel, 2003, p. 2). Sixth, whereas a passenger transportation network consists of nodes and links only, a freight supply network typically also consists of terminal nodes — such as warehouses, shunting yards, logistic centers, and freight hubs — "with specific characteristics concerning capacity and transfer delay time" (Friedrich et al., 2003, p. 2).
As noted above, transportation models are used to develop and analyze policy options. Passenger transportation models are regularly applied in both regional and international studies and often distinguish between public passenger transport systems (rail, tram, bus) and private passenger transport systems (bikes, passenger cars) (Friedrich, Haupt & Nokel, 2003). They mainly focus on individuals and model them as homogeneous agents or groups. In passenger transport modeling, a developer can choose from a range of commercial software packages that allow for traffic assignments, demand calculations, and network editing (Friedrich et al., 2003).
For passenger models, output is given in terms of points of transfer (nodes), links (routes), and users' travel times and costs (Friedrich et al., 2003). Net changes, on the other hand, "are measured in terms of vehicle miles of travel, passenger miles of travel, vehicle hours of travel, and passenger hours of travel (VMT, PMT, VHT, and PHT respectively)" (CTRE, 2007). More background on these metrics is available through the Bureau of Transportation Statistics, which publishes national data on travel behavior and system performance.
"Freight model complexity, outputs, and software tools"
"Common network basis enabling model adaptation"
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