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The crumple zone point in the article misses the mark. The reason why crumple zones don't exist on American railways is due to incompetent and centuries-out-of

The crumple zone point in the article misses the mark. The reason why crumple zones don't exist on American railways is due to incompetent and centuries-out-of-date Federal Railroad Administration regulation. FRA insists on railcars being able to withstand 800,000 lb of pressure without deformation, the so called "buff strength" requirement. This works OK for low speed gondolas and goods vans making up the bulk of the US freight network, but doesn't work at higher speeds or when there are passengers. If you want to see conventional, FRA-approved "buff strength" safety tested against "crash energy management" -- a broader concept including crumple zones -- watch this video [1]. The differences are striking. But to reiterate: don't blame crash safety on lacking technology. Blame it on bad regulation. [1] https://www.youtube.com/watch?v=NUpUJrk4QBE https://www.youtube.com/watch?v=NUpUJrk4QBE

NamTaf 9y ago
It's a little more nuanced than that. Old cars are essentially a flat base with a structure stuck on top. This forgoes crumple zones, yes, but it also results in a situation where one car body climbs over the other, as observed, causing the structure to shear in two. Anti-climb bars are a key technology in stopping this and were introduced after a number of large accidents where two passenger cars essentially became a pair of scissors and slid into one another. It also means that the cars stay roughly in line, ensuring that the reinfroced parts of the structure stay bearing on one another and transfer the load into the body rather than into the weak cabin area. If you think about it, the structure is very strong when pressed end-on, but as soon as one climbs it's essentially crushing from above/below and the structure is far weaker that way. Outdated regulation plays a part, particularly around the assumptions of where loads come from. As you mentioned, the buff crushing load assumes a longitudinal action only. Moreover, there has historically been minimal roll-over strength in cabins to protect pasengers. Change is disappointingly slow, however, and with asset lives of 50+ years due to the tough financial challenges facing particularly passenger rail, it takes a long time for new regulation to come into practice.

NamTaf 9y ago

It's a little more nuanced than that. Old cars are essentially a flat base with a structure stuck on top. This forgoes crumple zones, yes, but it also results in a situation where one car body climbs over the other, as observed, causing the structure to shear in two. Anti-climb bars are a key technology in stopping this and were introduced after a number of large accidents where two passenger cars essentially became a pair of scissors and slid into one another. It also means that the cars stay roughly in line, ensuring that the reinfroced parts of the structure stay bearing on one another and transfer the load into the body rather than into the weak cabin area. If you think about it, the structure is very strong when pressed end-on, but as soon as one climbs it's essentially crushing from above/below and the structure is far weaker that way. Outdated regulation plays a part, particularly around the assumptions of where loads come from. As you mentioned, the buff crushing load assumes a longitudinal action only. Moreover, there has historically been minimal roll-over strength in cabins to protect pasengers. Change is disappointingly slow, however, and with asset lives of 50+ years due to the tough financial challenges facing particularly passenger rail, it takes a long time for new regulation to come into practice.