Ritical Infrastructures -Railroad transportation ( Heavy Rail)

One of the major security issues facing us is how to safeguard railroad transportation and rail transportation hubs (switching yards, operations centers and the like) as well as rail-borne hazardous materials shipments against terrorist attacks. Review what has been done, evaluate whether the efforts to date have significantly reduced the challenge of terrorist attacks on rail transportation in the United States, and discuss what more could and should be done to make rail traffic more secure (be sure to consider the cost and feasibility of any recommendations).

Added on 22.03.2015 13:30
The type of railway is specifically the Heavy Rail system. Besides the three questions in the instructor notes already provided I need to address the following specific types of attacks on Heavy Rail systems: cyber (this could include the CAD/Scada system) active shooter, derailment( due to an IED), and CBRN. This paper is to specifically address US rail system but the historic attacks in London and Japan can be used as reference points as to how we have increased security or implemented processes that will mitigate or deter terrorist activity on the heavy rail system.
This paper is part of a group project so it will be combined with three other sections of trains to include cargo/freight, amtrac and lightrail, and hazardous materials.

Added on 22.03.2015 13:33
BTW I took a guess at the number of references as there was not specific guidance provided except that most should be scholarly references. I have found that DHS and TSA have a big part in the security of the US rail system and therefore may be a significant source of information.