With reference to Indian transport systems, consider the following statements :

1. The Indian railway system is the largest in the world.

2. National Highways cater to 45 percent of the total transport demand.

3. Among the states, Kerala has the highest density of surface road.

4. National Highway No. 7 is the longest in the country.

Which of these statements are correct?

I.A.S. (Pre) 2002