40th aniversary celebration
featured image: http://www.sftransitriders.org
The Transbay Tube is an underwater rail tunnel which carries Bay Area Rapid Transit‘s four transbay lines under San Francisco Bay between the cities of San Francisco and Oakland in California. The tube is 3.6 miles (5.8 km) long; including the approaches from the nearest stations (one of which is underground), it totals 6 miles (10 km) in length. It has a maximum depth of 135 feet (41 m) below sea level.
The tube was constructed on land, transported to the site, then submerged and fastened to the bottom (mostly by packing the sides with sand and gravel). This immersed tube technique is in contrast to bored tunneling, where rock is removed to leave a passage.
The Tube was the final segment to open in the original BART plan. All BART lines except the Richmond–Warm Springs line operate through the Transbay Tube, making it one of the busiest sections of the system in terms of passenger and train traffic. During peak commute times, over 28,000 passengers per hour travel through the tunnel with headways as low as 2.5 minutes. BART trains reach their highest speeds in the Tube, almost 80 miles per hour (130 km/h), more than double the average 36 miles per hour (58 km/h) speed in the remainder of the system.
“BART System Pt 1”