Structures constructed over obstructions to highways or waterways, such as canals or rivers, in order to provide continuous and convenient passages for purposes of trans- portation.

A bridge includes the necessary abutments and approaches that make it accessible. A public bridge that spans obstructions to a public highway is built on land owned by the state government for public use, while a private bridge is built on private property for the use of particular individuals who own it.

The construction of public bridges is a function of the state government by virtue of statute and is limited only by contractual or constitutional provisions. A state may exercise its power directly or delegate it to governmental agencies, such as a state highway commission. Cities and municipalities may erect bridges within their borders if authorized to do so by the state legislature. If a bridge is to be built within the borders of a state, the state has control of the project; but if the bridge connects two states, both states share involvement in the venture but must yield to the power of the federal government to supervise matters that have an effect on interstate commerce.

The state determines the location of a bridge subject to public safety and convenience considerations. It may grant a franchise — special privilege — to erect the bridge to a private bridge company that is chartered to build and maintain bridges. Such a corporation is considered a business affected with a public interest. A state agency may be organized to receive a franchise to construct a bridge.

The money needed to finance the construction of a bridge is usually raised by appropriations designed for the project — the sale of bonds pursuant to statute, special assessments, or taxation. The legislature decides whether construction expenses will be borne by the entire state or apportioned among its various subdivisions. It may create special taxing districts to finance the project as long as the district receives a proportional benefit from the bridge. State taxes cannot be used to defray the expense of purely local bridge obligations.

A reasonable toll may be charged for using the bridge when authorized by statute. The revenue collected can be used for governmental purposes as well as for the operating and maintenance expenses of the bridge.

The duty to maintain and repair bridges rests with the government agency or private company charged with their operation and maintenance. Statutes frequently require warning signs on guardrails and bridge approaches to caution drivers against known dangers. Civil or criminal liability may be imposed for damages resulting from the failure to maintain a bridge properly. No liability exists, however, for any damages incurred by an adjoining landowner from negligence or other wrongful conduct in the construction or maintenance of a bridge by a municipality or government agency unless provided by statute. A private company may be liable, however, if the law in the jurisdiction so provides.