Roger,
The ICC assumed responsibility for railroad accident investigations after passage of the Accident Reports Act of May 6, 1910. The file copies of these reports are part of the ICC records held by the National Archives (Record Group 134). They are part of the part of the recrods in the Bureau of Safety, Railroad Accident Investigation Reports, 1911-1963.
Summaries, and some single final reports, were published by the Government Printing Office as part of the series of publications of the ICC. These may be found in large libraries, for example, research universities,in their Federal Government Documents collection. I have found that not all accidents are covered in this series of accident summaries. For example, the boiler explosion of D&RGW 451 just east of Shavano Tank on Marshall Pass occurred on September 2, 1923. This was a fatal accident, but there is no mention in the published ICC Accident Summary for that quarter of 1923. Possibly the original report is on file as part of Record Group 134 in the National Archives. I have not personally checked this specific case.
Good luck with your research. As Rick and others have noted, plan on spending some time and lots of money on photocopies when you visit the National Archives facility where these records are held.
Charlie Mutschler
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