Context is important and near misses and failed safety incidents predating June 22, 2009, became ominous portents when viewed in retrospect. http://www.maryland-law.com/blog/fort-totten-metro-crash-opens-public-disclosures-of-problems.cfm
The bottom-line, Metro was not nearly as safe as it had seemed. Soon heads began to roll. http://www.maryland-law.com/blog/metro-crash-train-operator-fired.cfm
Train operators were fired or suspended from operating trains. http://www.maryland-law.com/blog/metro-near-miss-from-our-blogs-to-their-ears.cfm
Safety officials were fired and now Metro General Manager, John Catoe, has resigned. http://www.washingtonpost.com/wp-dyn/content/article/2010/01/14/AR2010011402917.html
Will his resignation make any difference? That answer is maybe yes and maybe no.
Yes, if his departure allows Metro to get a fresh start and become transparent as to past mistakes and problems which to this point have been swept under the rug or denied.
No, if his departure simply results in an attitude of "phew that nit-wit is gone business as usual."