To cut construction costs , the authority used an abandoned canal bed to build part of the system . Thus the underground section is only 2 – 3 meters beneath the street surface , and was the world 's shallowest metro . Years later , train frequency reduced and trains were commonly delayed . The rolling stocks themselves where dilapidated , with most seat covers torn off , and lights becoming dim . To change to a more modern and cleaner system in East Asia , a massive reconstruction , modernization and expansion plan was laid out in 2000 . In preparation , the system was closed on 1 September 2001 , with renovation totally started on 21 November after being delayed due to the terrorist attacks of 11 September . After introducing new rolling stocks , adding half-height platform screen doors and extending the line to , the line was completed at the end of 2005 and was re-opened on 12 June 2006
terrorist attacks of 11 September
September 11 attacks
Line 1 (Tianjin Metro)