The head-on collision between a MARC commuter train and Amtrak's
Capitol Limited at Georgetown Jct., MD (near Silver Spring) in February 1996 has been mentioned in several posts to this thread.
Here's a link to the NTSB's investigation report on the incident (it's a 155-page .pdf document): [
www.ntsb.gov]
There are some similarities between this collision and the Metrolink vs. UP collision at Chatsworth, so it's worth reading if one's interested.
The report includes photos, charts and graphs.
When reading the report, note that the signals are what's known as "Color Position Signals." Signal diagrams and a photo of such a signal are included in the report. I point this out because on occasion a reference to the MARC engineer's visual acuteness has been mentioned. With this type of block signal, color-blindness isn't a factor.