Line 1 of the Beijing Subway () is the oldest and one of the busiest lines of Beijing's mass transit rail network. Line 1 runs underneath Chang'an Avenue, the city's grand east–west thoroughfare, right through the heart of Beijing with stops on either side of Tiananmen Square. Line 1's color is red. Through operation with the Batong line started on August 29, 2021. Ridership As the oldest line of the Beijing Subway, Line 1 was also the most heavily used from the time the subway opened in 1971 until January 2013, when the near-completion of the Line 10 loop caused ridership on that line to surge past Line 1. Recent traffic relief efforts have been completed in recent years. The opening of the first phase of the parallel Line 6, caused an 8.46% decrease in daily demand and a 10-20% reduction in peak flow during rush hour. In addition Beijing BRT line 2 parallels the eastern section of Line 1. In the meantime between 2014 and 2015, Line 1 again upgraded its signals to a communications-based train control system allowing trains to run at headways as low as 1 minutes 45 seconds. However, during peak hours, sections of the line were reported in 2013 to still operate above 100% capacity. Hours of operation The first east-bound trains departs from Gucheng at 4:58am and Pingguoyuan at 5:10am. The first west-bound train departs Sihui at 4:56am and Sihui East at 5:05am. The last east-bound train leaves Pingguoyuan at 10:55pm. The last west-bound train leaves Sihui East at 11:15pm. Route Line 1's western terminus is , located in Shijingshan District. The line heads southeast to its second stop at Gucheng and from there runs straight east, following Chang'an Avenue all the way to its eastern terminus, in Chaoyang District, just beyond the 4th Ring Road. The line passes through Xidan, Wangfujing and Dongdan, among other important commercial centers of Xicheng and Dongcheng Districts, as well as the Beijing CBD near the China World Trade Center. The line is in length with 23 stations in operation. All stations except for and are underground. Stations Station list for Line 1 and Batong line of Beijing Subway, after the through operation started on August 29, 2021. History The first section of subway in Beijing officially started trial operation on January 15, 1971. It was long and ran between Beijing railway station to , which today is