The correct answer for this question is option 3: 180 days in advance ticket booking facility for passengers. This means that this particular initiative was not included as a thrust area in the Railway Budget 2015-16.

Let`s analyze the other options provided to better understand why they are not the correct answer:

Option 1: Online booking of disposable bed rolls - This initiative was included as a thrust area in the Railway Budget 2015-16. This means that the railway authorities aimed to provide the facility of online booking for disposable bed rolls to passengers.

Option 2: Defence Travel System to eliminate Warrants - This initiative was also included as a thrust area in the Railway Budget 2015-16. The railway authorities aimed to implement a Defence Travel System that would eliminate the use of warrants for travel purposes.

Option 4: Bio-toilets - This initiative was included as a thrust area in the Railway Budget 2015-16. The railway authorities aimed to install bio-toilets in trains as a part of their efforts towards a cleaner and greener environment.

Therefore, the explanation confirms that option 3 is the correct answer as it was not included as a thrust area in the Railway Budget 2015-16.