A light rail transit agency operates trains over a 25-km long single-track line. During the peak period, it operates five trains at 15-min headway. Train travels at an average speed of 50 km/hr. Each train has a cycle as shown below:
Travel from A to B: 30 min
Layover at B: 5 min
Travel from B to A: 30 min
Layover at A: 10 min
Total Cycle: 75 min
Using the Time-Space diagram, find how many double-tracked sections are needed to allow trains traveling in opposite directions to pass one another without delay?