A toll tunnel is a tunnel which people must pay a toll to pass through. The toll is typically used to fund the tunnel's maintenance, or to repay loans such as bonds which may have been issued to finance the construction of the tunnel. Toll tunnels are closely related to toll bridges, toll roads, and other thoroughfares for which tolls are instituted.
The amount of the toll for a given tunnel may vary. Many toll tunnels do not charge tolls for vehicles used in public transit, such as buses. They may charge higher tolls for vehicles with more than two axles or for large trucks, and may offer a discount or free pass to carpoolers. Depending on the design of the toll, people may pay a toll both ways, or, to save time on the return trip, a toll may only be required one way.
People can pay at a toll tunnel in several different ways. Many regions have automated systems which will deduct money from an account when a transponder passes by a device mounted at the entrance of the tunnel. It may also be possible to pay with cash, coin, or credit or debit card at a tollbooth. Automated payment booths may allow people to toss in the correct change for the toll, and some toll tunnels accept tokens and other methods of payment.
In some cases, a tunnel is established as a toll tunnel from the start, with transit authorities determining the amount of the toll. Tolls may be raised periodically as the costs associated with the tunnel increase. In other instances, tunnels may start out free, and a toll may be added later to address changing circumstances or conditions. Conversely, a toll tunnel can also turn into a free tunnel once satisfactory funds have been collected, as for example when tolls are used to repay a bond.
Typically, signs on the approach to the tunnel inform motorists that a toll must be paid to pass through, and alert motorists to the amount of the toll. Signage will also clearly indicate the last exit before the tunnel, offering people a chance to get off the road before paying the toll.
People who attempt to pass through a toll tunnel without paying the toll are usually subject to a fine. Some tolls have forgiveness programs for people who approach from the pay side and realize that they don't have money only after they cannot exit the roadway. In these cases, if the person agrees to sign up for an automated toll collection system, the fine for violating the toll may be waived.