Tremont Street subway, including Boylston station, was designated a National Historic Landmark. Of the two original stations, Boylston retained more of its original appearance, having undergone only minimal changes in over a century of continuous operation. The sub-passage between the platforms was closed around 1968, and permanently sealed off in 1981. In 1974, local students installed nine colorful panels in the station as part of the MBTA's arts program. The northbound outer track was removed in 1983. A planned renovation in 1986 was deferred by the station's historic status, though the disused outer tracks were fenced off. The MBTA again planned a renovation of the station – including elevators for accessibility – in 1990, but not did construct the project. In mid-2006, the MBTA installed brighter lighting at Boylston station, as well as modern electronic faregates and fare vending machines for the CharlieCard system. Plans for the South Boston Piers Transitway (later part of the Silver Line) were approved in 1993, calling for a bus rapid transit level at Boylston under the Green Line level. This portion was deferred in 1999, to become Phase III of the project. Silver Line service on the surface, running on Tremont Street, began stopping at Boylston in December 2001. After substantial increases in projected cost, Phase III was cancelled in 2010. In 2019, the MBTA indicated that Boylston was a "Tier II" accessibility priority pending the results of conceptual design. Incidents and accidents A few months before the station opened, there was a gas explosion at the corner of Tremont and Boylston Streets on March 4, 1897. Illuminating gas had been escaping from an underground main for two months into the cavity between the station's roof and the street above, before a horse-drawn trolley caused a spark which ignited the gas. Witnesses reported that a fireball engulfed the trolley, and burned several people and horses instantaneously. Six people were killed, and at least sixty were seriously injured. The station was spared any serious damage, as much of the force of the blast had radiated upward. On June 6, 1906, there was another explosion at Boylston station. The origin of the explosion was deemed to be the short-circuiting of the overhead lines in the station, which began to burn and catch fire. Because of the electrical nature of the fire, spraying water to stop the flames failed, and fire-fighters who attempted to do so were