I was looking for the answer to this question. It brought me here, but the closest question was [closed]. The most that I am aware of was when driver Pierre Levegh's race car killed 83 spectators at Le Mans: June 11th, 1955. Was wondering if this was the most or if there might be more. There were 84 deaths in all, including the driver. Technically it could be considered a 2-car accident, as his car launched off of another car. Maybe question should be 2-car accident?
The deadliest road accident not caused by an explosion that I could find took place in Sotouboua, Togo in 1965, where two trucks crashed into a crowd of dancers, killing 125 people. While this is widely reported on many "Deadliest Road Accident" lists (such as this one) the only contemporary source that I could find for it is the 1965 edition of Africa Diary (an Indian publication), which quotes:
(Standard Tanzania, Dar es Salaam) TOGO Trucks Kill 100 At Village Carnival. Two trucks that careened through a carnival crowd in the Togolese village of Sotouboua killed more than 100 persons and injured 100 others, the police reported on Dec. 6. The dead included an American Peace Corps worker, identified as James Driscoll of Buffalo, N.Y. [...]
Update: actually, searching Google Newspaper Archive for "James Driscoll" Sotouboua returns more reports.
As gleaned from my research, it seems that the road accident with the highest death toll in history was the Salang Tunnel fire, having occurred on November 3rd, 1982. Here is the link for the Wikipedia article: https://en.wikipedia.org/wiki/Salang_tunnel_fire. If the Soviet bulletin is to be believed (giving the one who posed the initial question the deference in this instance), than the undesirable title of deadliest road accident ever is ceded to the Los Alfaques disaster; link here: https://en.wikipedia.org/wiki/Los_Alfaques_Disaster
Consider the ruthless profiteer John D. Rockefeller's epigram: "I always tried to turn every disaster into an opportunity." I suppose in an infecund way you did :)
Single real road accident of a vehicle(truck) which caused highest deaths was near nagbavji in desuri ki nal Rajsthan in India on 8 sept 2007.This truck was carrying 150 pilgrimage to Ramdevji temple.In this accident truck plunged into 84 feet deep george.84 people died onthe spot.64 injured. In other high casualties of road accidents it is due to fire or othe no traffic reasons.. but in this case all casualties were purly due to road accident not due to subsequent other reasons. so it is the most death toll accident.
According to the National Safety Council, the worst single auto accident in U.S. history occurred on July 31, 1954 when 11 people died in a single car crash on Pine Mountain, eight miles south of Whitesburg, KY. There were 12 people in the vehicle, only one survived. The victims included three adults, a teenage girl and seven small children. Thomas Brown had purchased the 13 year old car, a 1941 Buick, the day before the accident. The car's brakes failed at the top of Pine Mountain and crashed into a cliff, overturned and caught fire. Hexie Maxie, the only survivor of the crash, was severely burned over most of his body and spent months in the hospital. He spent years grieving the loss of his family. Maxie died in 1982..
There is also the 1955 Le Mans disaster. 83 spectators were killed and 180 injured when the Mercedes 300 SLR of Pierre Levegh flew out of control near the pits, and major parts of the Mercedes like the engine and rear axle, sliced into a large crowd that had gathered near the pits.
A good deal of the fatalities resulted from poor crowd control... allowing spectators near the track where an out of control car could hit them.