How are the roads built?

There are almost 1.5 billion cars in the world, around 1.4 billion drivers in the world, and 70 million car trips each day. Chances are you are also using some sort of transport daily. Yet few people think about what the process of building roads for all these vehicles looks like. So, let's have a look into it.

Laying down a road may seem like a simple task: there are two points, and you just need to connect them. But in reality, things are much more complicated. Roads have to go through forests, deserts and mountains, above rivers and lakes, and to be able to resist the weight of trucks, heavy rain or any other harsh weather conditions.

Planning

Planning is the first step. In order to build a safe road, engineers need to pay attention to its geometry and materials used. Road geometry involves cross section, alignment and profile.
The cross-section is what you would see if the road was cut across. Under the surface (usually made of asphalt) are layers of different materials, that improve the road's stability and drainage. Upon a closer look at the surface itself, it should be visible that it is not perfectly flat, but curved, to get rid of the water more quickly. In turns, the surface is bent at an angle, not only because of water, but also to help drivers by creating inward centripetal force. This force prevents them from slipping off the wet or icy road.

Road cross section. Credits: https://commons.wikimedia.org/wiki/File:Green_St._cross_section.jpg

For a good horizontal alignment, road turns must have a long enough radius to enable drivers to steer without going off the road while maintaining speed.
Road profile is of great importance for heavier vehicles, as too steep road can make it hard for them to climb. For smaller vehicles, bigger problem is visibility. On too steep road, drivers can not see part of the road hidden behind the top, and their reaction time might be to slow to avoid the collision with other objects.
Another part of planning is solving problems associated with natural obstacles, such as soil, mountains, rivers and lakes. Engineers decide whether tunnels or bridges are needed, and if they are, how long, wide or strong they need to be. Geologists analyse the soil and choose appropriate materials and measures for the construction.
When planning is completed and approved by the authorities, construction starts.

Construction

Construction starts with earthwork. Large machines create a solid foundation for the road to make sure it can last longer. After the foundation, the road is paved using the most suitable material considering multiple conditions, including the amount of traffic as one of the most important. When safety banks and signs are added, construction is finished.

Road construction.

Now you know. The process of building a safe and efficient road is much more complicated than most people think but as the number of cars grows, it continues to improve and increase in complexity.