Death from a driverless vehicle

Introduction

Non-traffic (NT) motor vehicle crashes are those which do not occur on the public highway^1–4 and are mostly single-vehicle crashes on private roads, two-vehicle crashes in car parks or collisions with pedestrians on driveways.^1–3 NT crashes cause an estimated 262 fatalities and 115,000 injuries annually in the United States. ⁵ In Australia, such crashes have resulted in 12,837 people being hospitalised due to serious injuries in 2003–2004, ⁶ and 13,639 people being hospitalised during 2006–2007. ⁷ However, statistics from developing countries are hard to find as these cases are not properly documented. Major causes of NT fatalities are carbon monoxide from a vehicle’s engine, reversing, weather-induced excessive heat inside the vehicle and powered windows.^8,9 Also recorded are incidents caused by a vehicle falling on a person.^2,3 Every year in the United States, thousands of children are injured by motor vehicles in driveways or parking areas. ⁸ Toddlers and young children are at an increased risk of being struck by slow moving vehicles especially when reversing because children are short and may not be seen in a rear view mirror. ¹

Case report

The deceased was dead on arrival at the hospital. It was reported that he had been found lying unconscious by the road side with a lorry nearby. At autopsy (conducted at the first author's institute in India), the following external injuries were noted. An abrasion of size 10 × 7 cm was present over the postero-lateral aspect of the right elbow. A contusion with overlying patchy abrasions was present over the front and right flank of the lower abdomen, front of the thighs, right hip and lateral part of the right thigh with a total length of 48 cm. The scrotum was swollen and measured 17 × 12 cm in size. On incision, an estimated 300 ml of blood oozed out of the scrotum. Two superficially lacerated wounds of sizes 5 × 3 cm and 3 × 1 cm were present over the posterior aspect of the scrotum. A grazed abrasion of size 23 × 15 cm was present over the antero-medial aspect of the left thigh. On internal examination, an estimated 2 l of fluid blood and clotted blood was present in the peritoneal cavity. The anterior wall of the urinary bladder was contused and ruptured. The superior and inferior pubic rami of both the sides were fractured with contusion of the pelvic muscles. The stomach contained an estimated 200 ml of green-coloured fluid and emitted a peculiar smell. The rest of the examination was unremarkable except for pallor of the viscera. Chemical analysis revealed 267 mg% of ethyl alcohol in the stomach and its contents, whereas the liver and kidneys contained 230 mg%. Blood contained 138 mg% (w/v) of ethyl alcohol. The cause of death was haemorrhage resulting from multiple injuries.

Discussion

The history provided by the investigating officers was that the deceased was lying unconscious and moribund by the road side near a stationary lorry. The autopsy findings indicated hard and blunt force impact with an element of grazing and run over but there was no evidence of a hit-and-run traffic accident which was ruled out and the injury pattern did not suggest suicide. There were no eyewitnesses but the circumstantial evidence made death by homicide unlikely.

An attempt was made to reconstruct the probable sequence of events to assist the investigators. The deceased was found the previous evening roughly 15 feet from the road side. At autopsy, his blood alcohol concentration was 138 mg%. It was most likely that he had consumed alcohol at lunch time. He died at 3 am the next day, some 12 h later. Alcohol follows zero-order kinetics of metabolism. The rate of metabolism of alcohol by the liver is on average about 9–15 ml/h, reducing its concentration in the blood by about 12–15 mg/h. ¹⁰ Therefore, it was calculated that alcohol concentration at the time of the incident would have been 282–318 mg% which would have resulted in incoordination of thought, speech and action. ¹⁰

The three basic stages of alcohol intoxication are (1) excitement (blood alcohol concentration of 50–150 mg%), (2) incoordination (blood alcohol concentration of 150–300 mg%) and (3) narcosis (blood alcohol concentration of >300 mg%).¹⁰ The deceased was the lorry’s driver. In India, it is commonplace for drivers to rest in the shade under the lorry or by its side. So, it is likely the deceased driver did this but when parking his lorry he failed to or was unable to apply the parking brake properly. It is likely he was lying transversely and supine underneath the lorry when it rolled over him and indeed the contusion of 48 cm on his body roughly corresponds with the width of the two rear tyres. The lorry would have run over the body from the right side, turned him around causing the pelvic fracture and rupture of the bladder before coming to a halt due to the friction produced by the ground and bushes. Injury to the lower urinary tract occurs when there is a disruption of the pelvic ring. A total of 85% of urinary bladder ruptures are associated with pelvic fracture. ¹¹

Newton’s first law of motion states that a body cannot accelerate if no force acts on it. In other words, a body continues to be in a state of rest unless propelled by an external force. ¹² The force which is keeping the body (the lorry) static is the frictional force that exists between the tyres of the lorry and the ground (the static frictional force). ¹³ But what caused the lorry to move and run over the deceased? When vehicles move at high velocity, the air displaced by their motion acquires enough force to set other stationary objects or vehicles into motion once their static frictional force is overcome. The parking brake was not on and the lorry was on a natural downward slope allowing it to roll. The fingerprints of the deceased taken from the steering wheel, ignition key and the parking brake confirmed he was the last driver.

One study on NT pedestrian injuries found that 17% of cases were caused by driverless vehicles that had moved after they had been improperly parked. ¹ But they have not defined ‘improper parking’. A four-year survey reported that roll-away vehicles (unattended with no driver in control) were responsible for killing 15% of the non-occupants of NT crashes. ² Another similar three-year survey reported a higher rate of incidence of 19%. ³

In conclusion, the deceased, while drunk, failed to apply the lorry’s parking brake and lay to rest underneath it. The displaced air of other vehicles speeding along the highway created a force which was just sufficient to overcome the static frictional force and set the lorry in motion. After running over the deceased, the lorry rolled a little way downhill coming to a natural halt. Patchy abrasions of different sizes on the body roughly corresponded to the size of the stones on the ground further confirming the nature of death.

In this case, heavy consumption of alcohol indirectly caused the driver’s death and is responsible for countless deaths on the roads. It would be helpful if there were restrictions on the sale of alcohol by roadside hotels and restaurants with signboards along the highway that have warnings of speed limits and dangers of drunken driving. The police need to be in a position to monitor and enforce these regulations. Perhaps local volunteers can assist the police in black spots with speed breakers at regular intervals.