The construction, maintenance, and operation of transportation infrastructures are subject to five major types of constraints.
- Physical and environmental. Conventional physical constraints, such as topography and hydrography, have enduring impacts on transport infrastructure. They impose absolute and relative barriers that have shaped the development of transportation infrastructure for centuries. Any physical constraints impose higher construction and maintenance costs that can only be justified by higher economic and social opportunities the infrastructure may confer. Transportation network density and connectivity are usually at their highest in areas having low physical constraints, underlining the standard geographical influence on mobility and productivity. Climate constraints and weather disruptions are also constraining transportation infrastructure by increasing their construction and maintenance costs as well as impairing operations.
- Demand. Transport infrastructures are designed to meet a specific demand level by offering a defined capacity and level of service. For instance, a road segment can handle a specific number of vehicles per hour, or a port has the capacity to transship a defined quantity of cargo per work shift. Variations in the demand, often linked with seasonality, can create bottlenecks as parts of the network are not able to support additional volumes. Peak periods of traffic activity are often above the design capacity of the supporting infrastructure, creating delays. This also concerns accidents creating disruptions that have a higher probability to occur at high-traffic locations within the transport network.
- Financing. Transportation infrastructures are capital intensive, and securing financing can constrain their development or even their maintenance. Allocating scarce resources for transportation infrastructure requires careful consideration of the expected economic and social benefits. If these benefits are uncertain, infrastructure development could be impaired, which is particularly the case for peripheral areas. For some infrastructure, such as rail, airports, and port terminals, the private sector is willing to commit capital since the return on investment can be estimated. For other infrastructures, namely roads, the public sector can invest using a taxation base but with limited expectations of direct recovery of invested funds as the infrastructure is provided on the ground of public service. The joint availability of private and public funding can be a constraint in the development of transport infrastructure.
- Construction and maintenance. The construction and maintenance of transport infrastructure are intensive in construction, maintenance, and repair activities. These activities create disruptions in existing operations by reducing the available capacity (e.g. lane closure) and reducing operational speed. They require the organization of labor, equipment, and material resources that may not be readily available on-site and would require to be brought in, which comes at a cost. This is particularly the case in remote areas or developing economies where labor, equipment, and materials cannot be sourced locally.
- Regulations. Regulations impose restrictions on how transport infrastructure can be developed, owned, and operated, namely through compliance. Compliance with environmental regulations has become an important constraint in infrastructure development, adding costs and delays. Pressures from advocacy groups that increasingly see transport infrastructure negatively also impose additional costs, delays, and even the abandonment of transport infrastructure projects. The promoter of a transport infrastructure project may therefore face a multiplicity of regulations and advocacy groups.