>> we feel that had such a system been installed in this section of track, this accident would not have occurred. >> congress mandated that the system be installed throughout the nation's railroad system by the end of 2015 after a commuter train in 2008 collided with a freight train just outside of los angeles killing 25 people. and only a fraction of the nation's rail lines have it. but trains here in los angeles do. we accelerate the train in a simulator to over 90 miles an hour. it doesn't just slow you down, it stops you. >> if the engineer was incapacitated slowing it down doesn't do any good. you have to stop. >> this train has positive train control but most in the country do not. the deadline to install the system nationwide is at the end of this year but the industry says that deadline is impossible to meet. matt gutman, abc news, los angeles. >> arson investigators in washington, d.c. having a mystery on their hands. firefighters called to a blaze at a multi million dollar home. they found four bodies, three