damage is found. The largest to date was the 1989 Loma Prieta earthquake. During the 1989 earthquake, a train passing through the Tube was ordered to stop, although the operator reported no apparent motion. After inspection, the tube was found to be safe, and was reopened just six hours later, with regular service resuming system-wide twelve hours after the quake. Many area highways were damaged by the event, and with the Bay Bridge closed for a month due to a section of the upper deck falling onto the lower deck on a truss section of the east span, the Transbay Tube was the only passable direct way between San Francisco and Oakland. Pedestrians In October 2012 and August 2013, pedestrians entered the Tube through the station, prompting shutdowns and delays in transbay service. In late December 2016, a man entered the Tube through the portal at Embarcadero station and remained in it for more than an hour; while transit police were searching for him, trains continued to move through the Tube at slow speeds in manual mode. Equipment failure Service has been disrupted on multiple occasions after trains become stuck in the Transbay Tube, which is partially attributed to aging equipment. In addition to the 1979 fire, while moving through the Tube, a train split and was automatically stopped after a coupler failed in March 2010. Two maintenance vehicles collided within the Tube in September 2014, damaging a section of track and forcing BART traffic to rely on a single track. In January 2015, a train was forced to stop in the Tube after the brake inadvertently engaged on a car. A train in December 2016 was forced to switch to manual mode and proceed at reduced speed after stopping in the Tube, and another faulty brake forced a train to stop in the Tube in April 2017. Noise According to a 2010 survey by the San Francisco Chronicle, the Transbay Tube is the noisiest part of the BART system, with sound pressure levels inside the train reaching 100 decibels (comparable to a jackhammer). The noise, which according to BART "has been compared to banshees, screech owls, or Doctor Who's TARDIS run amok" is exacerbated by the concrete enclosure and the fact that tracks are curved when the tunnel crosses beneath the San Francisco–Oakland Bay Bridge, causing a high-pitched screeching sound. In 2015, after replacing and grinding down (smoothing) of