You never see them, but they're with you every time you fly. They record where you are going, how fast you're traveling and whether everything on your airplane is functioning normally. Their ability to withstand (抵挡) almost any disaster makes them seem like something out of a comic book. They're known as the black box.

When planes fall from the sky, as a Yemeni airliner did on its way to Comoros Islands in the India Ocean June 30, 2009, the black box is the best bet for identifying what went wrong. So when a French submarine detected the device's homing signal five days later, the discovery marked a huge step toward determining the cause of a tragedy in which 152 passengers were killed.

In 1958, Australian scientist David Warren developed a flight-memory recorder that would track basic information like altitude and direction. That was the first mode for a black box, which became a requirement on all U.S. commercial flights by 1960. Early model, often failed to withstand crashes, however, so in 1965 the device was completely redesigned and moved to the rear of the plane — the area least subject to impact — from its original position in the landing wells (起落架舱). The same year, the Federal Aviation Authority required that the boxes, which were never actually black, be painted orange or yellow to be visible.

Modern airplanes have two black boxes: a voice recorder, which tracks pilots' conversations, and a flight-data recorder, which monitors fuel levels, engine noises and other operating functions that help investigators reconstruct the aircraft’s final moments. Placed in an insulated（隔绝的）case and surrounded by a quarter-inch-thick panels of stainless steel, the boxes can withstand massive force and temperatures up to 2,000℉. When submerged (潜入水中), they’re also able to emit signals from depths of 20,000 ft.

Experts believe the boxes from Air France Flight 447, which crashed near Brazil on June 1, 2009, are in water nearly that deep, but statistics say they’re still likely to turn up. In the approximately 20 deep-sea crashes over the past 30 years, only one plane’s black boxes were never recovered.

You never see them, but they're with you every time you fly. They record where you are going, how fast you're traveling and whether everything on your airplane is functioning normally. Their ability to withstand almost any disaster makes them seem like something out of a comic book. They're known as the black box.

When planes fall from the sky, as a Yemeni airliner did on its way to Comoros Islands in the India Ocean June 30, 2009, the black box is the best bet for identifying what went wrong. So when a French submarine detected the device's homing signal five days later, the discovery marked a huge step toward determining the cause of a tragedy in which 152 passengers were killed.

In 1958, Australian scientist David Warren developed a flight-memory recorder that would track basic information like altitude and direction. That was the first mode for a black box, which became a requirement on all U.S. commercial flights by 1960. Early model, often failed to withstand crashes, however, so in 1965 the device was completely redesigned and moved to the rear of the plane — the area least subject to impact — from its original position in the landing wells. The same year, the Federal Aviation Authority required that the boxes, which were never actually black, be painted orange or yellow to be visible. Modern airplanes have two black boxes: a voice recorder, which tracks pilots' conversations, and a flight-data recorder, which monitors fuel levels, engine noises and other operating functions that help investigators reconstruct the aircraft’s final moments. Experts believe the boxes from Air France Flight 447, which crashed near Brazil on June 1, 2009, are in water nearly that deep, but statistics say they’re still likely to turn up. In the approximately 20 deep-sea crashes over the past 30 years, only one plane’s black boxes were never recovered.

Public transportation is beneficial for many reasons: it helps reduce traffic and air pollution, and supports more efficient land use means. Moreover, public transportation is cheaper than driving: It’s reported that a household can save around $9,823 a year by taking public transportation and living with one less car.

If you need another reason to consider using public transportation more often, consider this: taking public transit instead of driving your own vehicle reduces your chance of being in a traffic accident by more than 90%. According to the National Safety Council, there were 40,327 motor vehicle deaths in 2016. The majority of these deaths (23,714) were occupants in cars and light trucks. Only 249 passenger deaths in 2016 were the result of train accidents, and there were only 40 deaths of bus occupants in 2016.

Unfortunately, ridership on public transit is declining across the United States. One possibility may be the popularity of ride­sharing services like Uber and Lyft, although studies on that differ: some say ride­sharing services increase public transit usage, while others say they reduce it.

Even as ridership in the rest of the country decreases, the Orange County Transportation Authority’s OC Bus 360° system has seen a 19.6% increase since September 2017. They achieved this by adding services to the northern part of the county, where ridership was higher, and cutting some lesser­used routes in other parts. In those areas, they are instead trying OC Flex, an on­demand shuttle service offering unlimited rides for a few dollars per day.

To encourage people to take public transportation, the government has its part to do. Meanwhile, you can also take part. Try using public transportation to get to work or school once a week. Take some time to learn more about the bus routes and other public transportation choices in your area, and find ways to use it. You’ll be doing your part to reduce pollution, and decreasing your risk of being injured in an accident.