Following the tragic accident on the Samruddhi Expressway, where an AC sleeper coach bus overturned and caught fire killing 26 passengers, a detailed fire investigation report shed light on the cause of the devastating blaze. Connecting the dots from the evidence collected at the fire scene, the report submitted a theory that the front axle got dissociated from the bus due to the impact and collided with the diesel tank. The collision crumpled the tank causing the diesel inside to splash on to the surrounding area. The tank had approximately 350 litres of diesel at the time of the accident. The sudden compression of the diesel fuel within the tank resulted in an increased pressure. This led to the rupture of the tank at its opposite end, causing diesel to spill and spread rapidly. The diesel came in contact with hot exhaust, which ignited the fire.

 

The forensic investigation conducted by Mumbai-based Forensic Fire and Cyber Investigators has provided crucial insights into the sequence of events leading up to the incident and dispelled initial theories and speculations. According to the report, the driver was driving the Bus in the first lane at a speed of about 70-80 kmph when it reached Channel Number 332 near Sindkhedraja at about 1.32 am on July 1. While driving in the first lane, which is supposed to be used only for overtaking, the driver lost control over the vehicle and the front driver’s side wheel hit the sign board pillar which was placed just about 1.5 to 2 feet from the permitted path of drive in the first lane at Channel 332. The sign board got uprooted, along with its heavy RCC foundation, due to the impact. Subsequently, the same front wheel again rammed into the RCC Safety Wall which was about 10 feet from the MS Pillar. Both the rear wheels on the driver’s side also rammed into the RCC Safety Wall. The impact was so severe that the Rims (Discs) of the front and both rear wheels got damaged and bent. This had a huge impact on both the axles of the bus, the report stated. The report further suggested that the outer tyre of the rear wheels burst due to the severe impact and detached from the wheel, leaving the inner wheel exposed. Consequently, the inner wheel also got damaged and the vehicle was on the Rims of the RHS on the rear side.

 

  

Although the front axle was dissociated from the bus due to the force, it being underneath the body of the heavy bus did not drift away from the bus at that moment and still remained a part of the bus, so the bus kept rolling on the road on the two front wheels/ tyres without making any scratch on the road.The moment the bus overturned, the front axle, along with both the wheels, got physically separated from the bus, the report claimed. And during its natural movement, it struck the diesel tank on its path of coming to the ground, thus destroying the MS strips for the safety support of this diesel tank and crumpling it from the front side. Thus the diesel in the tank got splashed. There was about 350 litre diesel in the tank at the time of the accident. Diesel being non compressible fluid, due to sudden crumpling, the diesel inside of the tank got compressed and the pressure inside thus got increased. Due to this raised pressure, the other end of the diesel tank gave way and diesel started splashing and got poured from both the sides, the report suggested.

 

Splashing of diesel continued for a while as there was about 350 litres of diesel inside. During this time, because of overturning of the vehicle, the exhaust of the bus which is usually horizontal became vertical to the ground. Hence, the splashed diesel took some time to come in contact with the hot exhaust of the bus. And the moment the splashed diesel came in contact with the hot exhaust, fire was initiated. Diesel was already splashed everywhere in the surrounding area and once it caught fire, it took no time to spread thus killing the innocent passengers trapped inside of the bus, the report said.