Complete the following sentences in a suitable way

1. One of the best means to avoid traffic congestion and prevent traffic accidents in large cities is ……………………………………………………………….

2. The underground railway network solves the problems of public transport as well as …………………………………………………………………………...

3. The Underground is the most reliable means of travel because …….……..........

4. The Underground has no alternative in many European countries because …………………………………………………………………………………...

5. Building the metro through a busy city has been a challenge, because of the need to minimize disruption to road traffic and ……………………………….

6. In transport, we must expect the unexpected because it always happens. The major objective is to improve safety because ……………………………….......