Final answer:
The student's fear of train travel after a widely covered accident is an instance of the availability heuristic, where the ease of recalling an event skews perception of its frequency.
Step-by-step explanation:
The student's experience of becoming afraid to take a train due to a recent train wreck covered in the news is an example of the availability heuristic. This cognitive bias occurs when individuals estimate the likelihood of an event based on how easily they can recall similar instances. In this case, the constant media coverage made the train wreck highly memorable, leading the student to overestimate the frequency and likelihood of train accidents.