Road tunnels are underground passages designed for vehicles to travel through mountains, under rivers, or beneath urban areas. They help reduce traffic congestion on surface roads and provide a direct route for drivers. Tunnels are typically constructed using advanced engineering techniques to ensure safety and durability. These structures can vary in size and length, depending on their purpose and location. Some famous examples include the Channel Tunnel connecting England and France and the Lincoln Tunnel in New York City. Road tunnels often feature ventilation systems and lighting to enhance safety and visibility for drivers.