Shanghai Metro Collision

Ambulances wait outside a station of the Subway Line 10 after subway collision in Shanghai, east China, Tuesday, Sept. 27, 2011. A subway train in China's commercial center of Shanghai has smashed into the back of another train, injuring dozens of people. (AP Photo/Xinhua, Fan Jun)

Rescuers carry the injured after two subway trains collided in Shanghai, east China, Tuesday, Sept. 27, 2011. A subway train in China's commercial center of Shanghai has smashed into the back of another train, injuring dozens of people. (AP Photo/Xinhua, Fan Jun)

In this photo provided by China's Xinhua News Agency, rescuers carry the injured after two subway trains collided in Shanghai, east China, Tuesday, Sept. 27, 2011. A subway train in China's commercial center of Shanghai has smashed into the back of another train, injuring dozens of people. (AP Photo/Xinhua, Niu Yixin)

Passengers walk out from a subway tunnel after leaving a train involved in a collision in Shanghai on Tuesday Sept. 27, 2011. A Shanghai subway train rear ended another Tuesday, injuring more than 40 people in the latest trouble for the rapidly expanded transportation system in China's commercial center. (AP Photo)

A rescue worker carries an injured passenger out of the subway tunnel from a train involved in a collision in Shanghai on Tuesday Sept. 27, 2011. A Shanghai subway train rear ended another Tuesday, injuring more than 40 people in the latest trouble for the rapidly expanded transportation system in China's commercial center. (AP Photo)

Rescue workers carry an injured passenger in the subway tunnel from a train involved in a collision in Shanghai on Tuesday Sept. 27, 2011. A Shanghai subway train rear ended another Tuesday, injuring more than 40 people in the latest trouble for the rapidly expanded transportation system in China's commercial center. (AP Photo)

Rescue workers carry an injured passenger outside the entrance to a subway station where two trains crashed in Shanghai on Tuesday Sept. 27, 2011. A Shanghai subway train rear ended another Tuesday, injuring more than 40 people in the latest trouble for the rapidly expanded transportation system in China's commercial center. (AP Photo)

Rescue workers carry an injured passenger outside the entrance to a subway station where two trains crashed in Shanghai on Tuesday Sept. 27, 2011. A Shanghai subway train rear ended another Tuesday, injuring more than 40 people in the latest trouble for the rapidly expanded transportation system in China's commercial center. (AP Photo)

A rescue worker tend to passengers injured after a subway train accident in Shanghai on Tuesday Sept. 27, 2011. A Shanghai subway train rear ended another Tuesday, injuring more than 40 people in the latest trouble for the rapidly expanded transportation system in China's commercial center. (AP Photo)

Rescue workers walk out from the emergency exit of a train involved in a collision in Shanghai, China, on Tuesday Sept. 27, 2011. A Shanghai subway train rear ended another Tuesday, injuring more than 40 people in the latest trouble for the rapidly expanded transportation system in China's commercial center. (AP Photo)