Roads are everywhere. We use them every day but hardly think about them.
They are so much a part of daily life that the English language is full of phrases about roads.
When we say that a project "hits a bump in the road," we mean a problem has occurred,
and a person who takes "the road less traveled" has chosen an unusual way of life.
Roads developed along with human civilization, so we have to go a long way back to find a time before roads.
During the Ice Age seventy thousand years ago, humans lived in caves and hunted wild animals with weapons made of sticks and stones.
The ground was covered with snow, and hunters easily lost their way in the thick forests.
They would mark their tracks with branches so that they could find their way home.
That is how the first paths were created.
Around 10,000 BC, the earth's climate began to warm up.
Tribes of people started to live in villages, where they grew crops and kept tame animals.
They also learned how to make tools out of bronze and iron.
They needed roads to travel to each other's villages,
so they cleared paths through forests and across plains and built simple dirt roads with their tools.
They used primitive carts to carry heavy loads on these first roads.
Dirt roads, however, twisted and turned and did not last long.
Also they were not convenient in bad weather.
Rain would turn the dirt to mud, making it impossible for people or animals to pull their carts.
Roads could remain unusable for days after a heavy rain.
Over time the footsteps and wheels from all the traffic would create deep grooves in the roads.
These narrow ruts made walking and pulling carts even more difficult.
But despite all these problems, it was a long time before anyone improved on dirt roads.
The first modern roads were built at the height of the Roman Empire in the first century AD.
The Roman Empire was very powerful. It ruled over three continents and had a very large army.
In order to move their soldiers around the vast empire, the Roman emperors needed well-built roads.
Fortunately the Romans were great engineers.
The roads they built ran perfectly straight for hundreds of kilometers.
The Romans built their roads from stones instead of dirt, and laid gravel and cement over the stones to give the roads a hard, smooth surface.
They even carefully shaped their roads so that the center was a little higher than the edges.
That way, rainwater would not collect in pools but would run off to the sides.
Roman roads were the first to have a drainage system to keep them from flooding.
Another famous saying is that "all roads lead to Rome," and during the time of the Roman Empire, this was certainly true.
But it remained true for long after and, in some ways, it is still true today.
The Roman roads were so convenient that everyone used them, not just the soldiers.
People traveled from town to town, traded goods, and sent messages using the Roman roads.
Villages and towns located along the roads grew larger, while towns farther away became smaller.
The Romans built their roads so well that many of them lasted until the nineteenth century!
More than a thousand years after the last Roman emperor died, people were still using the straight, durable roads that once connected the Roman Empire.
In fact, many of Europe's modern highways follow those same routes today.
By the time of the Industrial Revolution in the late eighteenth century, new road technologies were needed.
Goods manufactured in factories had to be transported to and from great, crowded cities like London and Paris.
The train was invented, and people began to travel much more than before.
An engineer from Scotland named John McAdam revolutionized the way roads were built.
His method, called the macadam, is still used today.
He crushed stone into three specific sizes and built his roads in layers,
using the largest stones for the bottom layer and the smallest stones for the top layer.
By wetting the road and then compacting it with a heavy roller, the stones locked together to create a firm surface.
Macadam roads were more durable, less expensive, and easier to build, but they were very dusty.
With the invention of the automobile, a smoother, cleaner surface was needed.
Today paved roads are covered in asphalt.
Asphalt was first used in France in 1824 on the Champs-Elysees boulevard in Paris.
Asphalt was not popular at first because it was rough, but a few years later, a man called Edward de Smedt perfected it.
In 1872 he produced a higher-grade asphalt, and the first street to be paved using his asphalt was Fifth Avenue in New York.
By the turn of the twentieth century, cars, bicycles, and motorbikes were everywhere.
After World War II cities were getting overcrowded, and people began to experience the first traffic jams.
The first highways were built in the 1960s.
Highways are designed for safe, fast travel.
They have no traffic lights, no stop signs, and no parking.
Today highways are the most popular method of ground travel.
Even though advances in road-building have greatly improved travel, many cities are now polluted and overcrowded with traffic.
And traffic jams are not just bad for drivers, they are also bad for the environment.
Cars and trucks contribute to unhealthy smog and global warming.
While new electric and hybrid cars are much less polluting, many cities have decided to make parts of their downtown off limits to cars.
The historic downtown of Copenhagen in Denmark is Europe's oldest and largest car-free zone.
People walk its streets just like people did on the first roads thousands of years ago.
Roads have been part of human civilization since hunters first marked their footsteps in the snow.
So whether we travel by foot, by car, or in some new vehicle of the future, wherever we go, there will always be roads.