The road infrastructure of a particular region is the total sum of the streets, roads, and highways in place. It also encompasses the signage, interchanges, bridges, and rights of way associated with the roads. Complete inventories of these public assets are frequently required by local jurisdictions. The status of road infrastructure is often evaluated according to road condition, safety, and capacity. Funding decisions for road repair, replacement, or expansion are made based on the status of roads' infrastructure and future needs as modeled by traffic planners.
To quantify road condition, safety, and capacity, useful data must be put in a format accessible to those who gather the data and those who use it. The rigorous and consistent documentation of road infrastructure is one of the keys to maintaining the system in an efficient manner. A well-designed database may present raw data and be manipulated to run simulations of traffic patterns based on detailed data.
The detailed level of data at the segment level contrasts with typical high-level planning conducted by traffic engineers. A particular curve may be responsible for limiting the overall capacity of a highway, yet that fact may not be visible without some segment-by-segment analysis. Likewise, a road may be labeled as having an above-average accident rate, when the problem lies in poor signage.
Counties, states, and nations allocate significant resources to provide a road infrastructure capable of carrying on the commerce of businesses and the transportation needs of citizens. In the United States, road infrastructure is maintained through departmental budgets and by collection of tolls and special taxes applied to gasoline sales. While considered an asset, roads actually represent an ongoing maintenance and service burden once built.
As a funding mechanism for road infrastructure, a public-private partnership (PPP) is more common in Europe and Australia than in the United States. Surveys of PPPs around the world by the United States Department of Transportation have concluded the PPP model is viable. In PPPs, the financing and building of road infrastructure are undertaken by private companies. In the majority of cases, the life-cycle maintenance and improvement responsibilities are assumed as well. Government agencies take more of a client role, paying fees in return for transportation services.
