Trade, transport and computers

Seif wants to visit his cousin, who lives 10 kilometres away. The family car is at the garage. Walking would take about two hours, which is too long. A bicycle is cheap and good for short trips in nice weather, but 10 kilometres is far on a hot day. A car is fast and goes from door to door, but it uses fuel and makes the air dirtier. A truck carries heavy cargo but is not made for passengers. A train carries many people far, but only between stations. An aeroplane is for very long trips and costs a lot. To choose, we think about the factors: the distance, the cost, the time, the weather, how many people or how much cargo, and the effect on the environment. Engineers design transport systems in a similar way. They start with a need and a goal. Then they think about five parts: 1 location (where will it go: land, water or air?), 2 users (who and how many?), 3 resources needed, 4 results (what will it do?) and 5 feedback (how do we check that it works well?). They also try to protect the environment.