This paper, planned for a special issue of Osiris, explores how spectacular failures in complex systems transformed the category of “accidents” in the middle decades of the nineteenth century. The vast expansion of Victorian rail networks in the 1840s and 1850s helped create a society of strangers that defined both modern Britain and modernity itself. But that expansion also created deep anxieties about the dangers of large-scale systems, their tendency to multiply horrific accidents, and even to make those accidents inevitable. Whereas accidents had previously been freak occurrences, by the 1860s, railway systems were seen as the material sites where impossible conjunctions of imperfect materials, flawed humans, and failing machines routinely came together to threaten a newly nervous public. The paper examines the attempts to develop a systematic knowledge of technological accidents and their shifting nature, from freak occurrence to looming inevitability. It highlights the role of the anxious traveling public in that transformation — a public these accidents helped create. It explores the suite of modern remedies — timetables, management practices, system maps — designed to bring accidents under control. And it focuses on the rise of a way of thinking about technological failures that tied anxieties about unreliable humans to fears of untrustworthy machines. In doing so, the paper aims to remind us how “making things work” has always been bound up with fraught questions over why and how things fail. Victorian observers furnished one particularly powerful and enduring way of thinking about accidents, responsibility, and social order in an age of distributed causality.