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> The weight limit was 26 tons, not 2 tons. 85% of PATransit busses are from the 1996 acquisition (Cummins ISL, ISB, IS9; Voith 864; Allison D) those busses we

> The weight limit was 26 tons, not 2 tons. 85% of PATransit busses are from the 1996 acquisition (Cummins ISL, ISB, IS9; Voith 864; Allison D) those busses weigh either 24 or 25 tons. Their other busses (except the 28x airport flyer) are heavier. Other than the flyers, SEPTA's lightest bus is 24 tons. Some of them, like the XE40 or the X12, are significantly heavier. About 1/5 of PATransit's fleet is over-weight for this bridge without a single person on board. 26 tons is so little of a load that nobody should ever have been sending a bus over it. The 2 tons is for the human load, above and beyond the weight of the vehicle. The vehicle already accounts for 24 of the 26 tons, bare minimum by definition. If it was an XE40, it was two tons over load without even a driver. That is to say, "there's more weight here than just the human beings. You should also consider the bus itself." I did spell this out, but it was in a different comment tree. I thought I had here too. Sorry; I could have been clearer. Someone in a different thread pointed out that it was a three axle bus. I've been making this case based on two-axle busses being too heavy. PATransit's lightest three-axle bus is MAN SG 220 GAWR, just shy of 30 tons curb weight, which is nearly 4 tons over limit. Look, if you're from Pittsburgh, the last thing you want to do is stand up for PennDOT. But looking at the numbers, to me, this really looks like "too big bus," not "bridge go boom" Not all infrastructure failures are the fault of the infrastructure. Many, maybe even most, but not all. It's important to differentiate.

steveklabnik 5y ago
I'm curious about this, where did you get the info about the fleet? Wikipedia suggests that the fleet is almost entirely Gillig, but has no citations. I couldn't find it on the Port Authority's site either. > Look, if you're from Pittsburgh, the last thing you want to do is stand up for PennDOT. Agreed, but "runs bus service every ~30 minutes where a single bus would make the entire bridge overweight" would be an entirely new level of "I can't believe it."
- JohnHaugeland 5y ago
  > Agreed, but "runs bus service every ~30 minutes where a single bus would make the entire bridge overweight" would be an entirely new level of "I can't believe it." structural damage is incremental. situations where the trigger is dramatically smaller than peak load are quite common. consider the florida condominum: it collapsed in fair weather, despite that under rain load it would have hundreds of tons more support carry. you've seen many videos on youtube where a sinkhole opened up under a small car on a large road which carries freight. this is one of the things you're taught very early in the relevant schooling. you've tried to pull my card in fairly aggressive ways several times in this thread. it's making me somewhat uncomfortable.
  - steveklabnik 5y ago
    I am sorry to make you feel uncomfortable. I am trying to make sense of something that happened to something very near and dear to me. Not trying to do anything to you. I asked the question about the fleet not to "pull your card" but because I am interested and spent a bunch of time trying to find this information and could not, and am interested in how you came across it. You started off with "look up the weight of a bus" and I that's exactly what I tried to do, and what I found is not the same as what you're saying, so I asked for where you got your data to see if I found bad data or you did. (And yes, absolutely structural damage is incremental, but that's not material to the claim that this bus weighs over 26 tons.)
    - JohnHaugeland 5y ago
      [flagged]
saalweachter 5y ago
You sound like someone who knows about this, and I'm just someone Googling [how much bus weigh], so I'm hesitant to keep posting on this topic, but I'm still really curious where you're getting these weights from. All of my Googling keeps turning up weights in the 15-20 ton range for fully loaded busses, with city busses more towards the low end of that range, so I'm curious why these busses would be almost twice as heavy. EDIT: Ah-ha, looking at the picture shows it was an articulated bus, and Googling [how much does an articulated bus weigh] gives weights in the range you listed. So yeah, you're right and that bus should not have been going over that bridge.

steveklabnik 5y ago

I'm curious about this, where did you get the info about the fleet? Wikipedia suggests that the fleet is almost entirely Gillig, but has no citations. I couldn't find it on the Port Authority's site either. > Look, if you're from Pittsburgh, the last thing you want to do is stand up for PennDOT. Agreed, but "runs bus service every ~30 minutes where a single bus would make the entire bridge overweight" would be an entirely new level of "I can't believe it."

JohnHaugeland 5y ago
> Agreed, but "runs bus service every ~30 minutes where a single bus would make the entire bridge overweight" would be an entirely new level of "I can't believe it." structural damage is incremental. situations where the trigger is dramatically smaller than peak load are quite common. consider the florida condominum: it collapsed in fair weather, despite that under rain load it would have hundreds of tons more support carry. you've seen many videos on youtube where a sinkhole opened up under a small car on a large road which carries freight. this is one of the things you're taught very early in the relevant schooling. you've tried to pull my card in fairly aggressive ways several times in this thread. it's making me somewhat uncomfortable.
- steveklabnik 5y ago
  I am sorry to make you feel uncomfortable. I am trying to make sense of something that happened to something very near and dear to me. Not trying to do anything to you. I asked the question about the fleet not to "pull your card" but because I am interested and spent a bunch of time trying to find this information and could not, and am interested in how you came across it. You started off with "look up the weight of a bus" and I that's exactly what I tried to do, and what I found is not the same as what you're saying, so I asked for where you got your data to see if I found bad data or you did. (And yes, absolutely structural damage is incremental, but that's not material to the claim that this bus weighs over 26 tons.)
  - JohnHaugeland 5y ago
    [flagged]

saalweachter 5y ago

You sound like someone who knows about this, and I'm just someone Googling [how much bus weigh], so I'm hesitant to keep posting on this topic, but I'm still really curious where you're getting these weights from. All of my Googling keeps turning up weights in the 15-20 ton range for fully loaded busses, with city busses more towards the low end of that range, so I'm curious why these busses would be almost twice as heavy. EDIT: Ah-ha, looking at the picture shows it was an articulated bus, and Googling [how much does an articulated bus weigh] gives weights in the range you listed. So yeah, you're right and that bus should not have been going over that bridge.