The Virginia Department of Transportation, also known as VDOT, is responsible for building, maintaining and operating roads, bridges and tunnels in Virginia. The department is administered by the commonwealth of Virginia. It provides funding for airports, seaports, rail and public transportation systems. The Virginia Department of Transportation has one of the largest state-maintained highway systems in the United States. The department also operates a center that offers tips for driving safely through construction sites. In addition, it maintains several biking and walking trails. The Virginia Department of Transportation conducts projects and studies for determining the need and impact of proposed highway projects statewide.