Okay, last one, I promise (unless I find a better video
). This is the original dashcam, but starting a little earlier. After watching this video in 720p, here are my thoughts:
1) This interchange has a lot of stuff going on in a short distance. The entering traffic has two lanes merging down to one, then an off/on ramp for the fuel center, then the Ivanovskoy exit, all in less than 500m / a quarter mile.
2) The silver van/bus (first seen at the 15 second mark) should have already been in his rightmost lane for the Ivanovskoy exit, but was two lanes over. He crossed two lanes, then slammed on the brakes in an effort to merge into traffic coming from the fuel center.
3) The gas truck driver may have been distracted by the driver of the dashcam car crossing into his lane because of some debris in the road (19 second mark), and did not react fast enough to the silver van moving into his lane and braking.
4) Just after the impact (~33 second mark), you can see one or more cylinders venting a white cloud of gas as they bounce off the road - then there is an explosion. I would say loose gas cylinders rupturing or breaking their valves, then an electrical spark or sparks from steel cylinders striking the pavement, is what caused the rapid fire.