On packed subways and crowded highways, billions of people participate in a short-distance population shift twice a day: the rhythmic ritual of the daily commute to and from work.
In the photo above, commuters cling to an overcrowded passenger train in Soweto, South Africa, on Sept. 8, 2014.
More than 300 million people use the United States' transport systems every day, and in 2012 a whopping 76 percent of them got to work by driving alone, a U.S. Department of Transportation report out last week noted. That can make for a lot of gridlock.
In the photo above, cars approach San Francisco on the Bay Bridge on Sept. 3.
Highways clogged with bumper-to-bumper cars may be the go-to image of rush-hour traffic. But peer deeper and you'll find others.
Train commuters, like these in Beijing on Sept. 22, frequently experience crowded cars during their commute.
In Amsterdam, bike commuters get off a free ferry on Sept. 8. Thirty-eight percent of Amsterdam's commuters travel by bicycle.
Commuters in Bangkok get off a motorized boat during rush hour on a pier at the Saen Saeb canal in Bangkok, Thailand, on Sept. 15.
Thousands of motor scooters wait at a stoplight during the morning commute in Taipei, Taiwan, on Sept. 4. There are 15.09 million motorcycles in Taiwan, or 67.6 for every 100 people.
North Korean commuters ride on a subway in Pyongyang, North Korea, on Sept 1. Foreign visitors are usually only allowed to take one to two stops on Pyongyang's north-south Chollima subway line.
Irma Ortiz applies makeup while waiting in line at the Western Hemisphere's busiest border crossing in Tijuana, Mexico, on Sept. 10. An average of 50,000 cars and 25,000 pedestrians cross daily through the San Ysidro Port of Entry - many waiting for hours on their way to jobs, schools and shopping malls in the U.S.
Bolivia's cable-car between La Paz and El Alto is the largest of its kind in the world. Here, their cabins break through the fog on Sept. 18. The system was completed earlier this year.
A man closes his eyes as he stands with other commuters in a crowded metro car during rush hour in Rio de Janeiro on Sept. 17.
A boy sells coconuts during rush hour in the middle of heavy traffic near an intersection in New Delhi, India, on Sept. 10.
A woman smells a bouquet while walking on the Wilshire Boulevard overpass as traffic moves along the 110 Freeway during evening rush hour in Los Angeles on Sept. 9.