a viaduct was built in 1997 along the original freeway between Xizhi and the Wugu District of New Taipei to serve as a bypass for traffic not exiting and entering the freeway within Taipei. The construction of a freeway connecting the Taipei metropolitan area and Yilan County began in 1991 and was completed in June 2006. It includes a tunnel (Hsuehshan Tunnel), which is the ninth-longest road tunnel in the world. An extension from Yilan County to Hualien County is planned. However, its construction is being delayed by environmental concerns. On January 2, 2014, the toll system was converted to a distance-based one. Tolls are no longer collected at toll booths but automatically by electronic toll collection (ETC). Features Length, exits, and entrances Every one tenth of a kilometer is marked on the freeway with Arabic numerals to indicate freeway mileage, which indicates the number of kilometers away from the northern end or western end of the freeway. Exit numbers are based on the freeway mileage. With the notable exception of exit-only signs, which are only expressed in Chinese (but with a right arrow indicating an exit-only lane), exit notification and system route reminder signs in the freeway system are almost identical to their US counterparts. There are four types of exit notification signs. The first notification sign appears two kilometers before the exit, providing the destination name and an Exit 2 km notice. The second sign appears one kilometer before the exit, providing the destination name and a Right Lane notice. The Right Lane notice warns the exiting driver to start switching to the right lane in preparation to exit and does not necessarily indicate that the right lane is an exit-only lane. The third sign appears a few hundred meters before the exit, providing the destination name and a right tilted arrow. The fourth sign is located at the exit and says Exit with a tilted right arrow. Exit notification signs were slightly altered in December 2005. The green exit mileage label on top of the exit notification sign has been replaced with a yellow exit mileage label accompanied with the Chinese code name of the interchange. The Chinese code name of the interchange does not necessarily reflect the destinations listed on the exit signs and may represent the general location of the freeway interchange. Long rectangular-dash dividers usually separate normal lanes. Short rectangular-dash dividers usually indicates a