(CNN)Here's some information about Washington, DC's subway system, generally called the "Metro." The Washington Metropolitan Area Transit Authority operates Metrorail, the third largest heavy rail system in the United States, and oversees the country's sixth largest bus system.
Washington, DC Metro System Fast Facts
Ridership on the rail system in 2018 totaled approximately 174 million trips; for the bus system, the total was 121 million trips and 2.3 million trips on MetroAccess, the paratransit service.
The rail and bus system serves a population of four million passengers.
The routes include trips from Washington, DC to Maryland (Montgomery and Prince George's counties) and Virginia (Arlington, Fairfax, and Loudoun counties, and the towns of Alexandria, Fairfax and Falls Church).
The Metrorail includes six train lines and covers 118 miles.
Metrobus had 10,687 bus stops, as of 2018.
As of 2017, average weekday ridership for Metrorail was 626,000.
The system is patrolled by the Metro Transit Police Department.
The Metro's operations control center has hotlines to every police and fire department in the regions serviced.
Emergency call boxes are located on station platforms that connect to the operations control center. The boxes have a button to shut down third-rail power during emergencies.
Outdoor Metrorail tracks are blocked by fencing that alerts central control to disturbances, breaks and any tilting.
February 20, 1967 - The Washington Metropolitan Area Transit Authority is created.
December 9, 1969 - Construction on the Metrorail begins.
1973 - Four bus systems are acquired.
March 27, 1976 - The first portion of the Metrorail system opens to the public.
January 13, 1982 - A subway train derails during afternoon rush hour near the Federal Triangle on the Orange line. Three people are killed and 25 injured.
January 13, 2001 - The final portion of Metrorail is completed.
2004 - Three new subway stations open, two on the Blue line and one on the Red line.
January 20, 2009 - The Metro sets a record with 1,544,721 rail and bus trips on the day of President Barack Obama's inauguration.
June 22, 2009 - Two subway cars collide on the Red Line in Washington, DC during afternoon rush hour. Nine people are killed and more than 70 are injured.
July 26, 2014 - The Silver Line opens, adding an additional 11.7 miles to Washington, DC's Metro.
January 12, 2015 - One person is killed and more than 80 others are hospitalized after a train station at L'Enfant Plaza fills with smoke. The smoke condition was caused by an "electrical arcing accident" on the third rail, according to the National Transportation Safety Board. The incident prompts the Federal Transit Administration to begin work on a report identifying Metrorail safety issues.
June 17, 2015 - The FTA releases its report, which identifies numerous hazards throughout the Metrorail system. The problems include an understaffed control center, employees using personal cellphones while on duty and a poor radio communications network.
March 14, 2016 - An electrical fire in a Metro tunnel causes major delays on the Orange, Silver and Blue lines.
March 16-17, 2016 - The entire Metrorail system is shut down for safety inspections. The closure lasts from midnight on March 16 until 5 a.m. on March 17.
May 3, 2016 - The National Transportation and Safety Board releases its report on the fatal Metrorail accident in January, outlining safety issues and infrastructure problems in the Metrorail system.
2016-2017 - WMATA conducts a series of 16 "safety surges" during a program called SafeTrack. Each safety surge involves fast-tracked repairs and maintenance to address NTSB and FTA safety recommendations for the Metrorail system.
January 21, 2017 - According to a tweet from WMATA, 1,001,616 rail trips are taken on the day of the Women's March in Washington. That sets a record for Saturday ridership on Metrorail.