There are four major types of challenges that affect transport systems:
- Capacity. A basic constraint concerns appropriate capacity, both along a transport route and at a terminal. The capacity of a transport system is often restricted by its circulation bottlenecks.
- Transfer. Transfer points are crucial as they permit the interface between different transport systems, a role commonly served by hubs or gateways. For instance, a port is commonly the interface between maritime and inland systems of circulation while an airport can act as a hub connecting different air networks such as regional and international.
- Reliability. A multidimensional problem that concerns the expectation that a movement will occur within a specific time and cost range. While a route could be shorter, it may not be as reliable as a longer route. Congestion is a common factor impairing the reliability of a transport system since it can impose inconsistent time delays and additional costs.
- Integration. Involves exploiting the benefits of each transport mode so that flows become more reliable or less costly. Integration is sought by intermodal transportation, but also by airline companies connecting different parts of the world.