Watching the video NutLoose posted raises a few questions.
Why did the truck bomb (if that's what it was) detonate where it did? A better spot would seem to be at the apex of the road at the steel arch structure. As well as taking out the road section there would be an additional damage to the supporting cables. Plus possible damage to the rail bridge girders.
Also why detonate in the outside lane? Far better to move over one lane, closer to the rail tracks. More chance of causing damage to the opposite carriageway across the barrier.
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Alternatively, if it's a false flag attack then why detonate alongside a fuel train? Why take out an incline section if a flat roadway section might prove easier to repair