have they taken any measures to prevent terrorism in there?
Yes -  a Ferrara Fire Apparatus Hazardous Materials Response Truck went into service
New York City Subway
On July 22, 2005, in response to bombings in London, the New York City Transit Police introduced a new policy of randomly searching passengers' bags as they approached turnstiles. The NYPD claimed that no form of racial profiling would be conducted when these searches actually took place. The NYPD has come under fire from some groups that claim purely random searches without any form of threat assessment would be ineffectual. Donna Lieberman, Executive Director of the NYCLU, stated, "This NYPD bag search policy is unprecedented, unlawful and ineffective. It is essential that police be aggressive in maintaining security in public transportation. But our very real concerns about terrorism do not justify the NYPD subjecting millions of innocent people to suspicionless searches in a way that does not identify any person seeking to engage in terrorist activity and is unlikely to have any meaningful deterrent effect on terrorist activity." The searches were upheld by the United States Court 
where is nostrand avenue station (ind fulton street line) located? Bedford–Stuyvesant, Brooklyn, New York City what does the mentioned street line signify? It is a rapid transit line of the IND Division of the New York City Subway. were there any accidents happened at the subway? Yes - 64 major train accidents since 1918;  The 1995 Williamsburg Bridge crash; and  derailments have also taken place
wiki:19918545
New York City Subway [SEP] Terrorism prevention
On July 22, 2005, in response to bombings in London, the New York City Transit Police introduced a new policy of randomly searching passengers' bags as they approached turnstiles. The NYPD claimed that no form of racial profiling would be conducted when these searches actually took place. The NYPD has come under fire from some groups that claim purely random searches without any form of threat assessment would be ineffectual. Donna Lieberman, Executive Director of the NYCLU, stated, "This NYPD bag search policy is unprecedented, unlawful and ineffective. It is essential that police be aggressive in maintaining security in public transportation.