It shows how speed, weather and impairments affect stopping distances and result in crashes and pedestrian deaths.
By logging on to here motorists can see how long it takes to stop when a child dashes out from behind a van to retrieve a ball bouncing in the road.
The speed of the car in the simulator can be set at 5mph intervals between 20mph and 45mph to check their stopping distance in normal conditions. But they can also see how using a mobile phone, alcohol or wet weather makes things more dangerous.
Details are given of their thinking distance, braking distance and overall stopping distance and the pedestrian's likely fate. A replay button shows an aerial view of the scene with the thinking and braking distances marked on the road to highlight how far the car travels and the point where the car hits the child.
The simulator has been produced with support from the Department for Transport to help drivers improve their road safety knowledge.
Duncan Vernon, RoSPA road safety project officer, said: "We hope that after using the simulator motorists will have a much clearer idea of how speeding, drink and mobile phones put all road users in danger.
"They can compare how using a mobile phone or being over the drink-drive limit affects their ability to stop.
"Speeding or driving too fast for the conditions causes thousands of serious accidents each year. Drinking and driving remains a major problem in this country and it has been shown that using a mobile phone - whether hand-held or hands-free - makes you four times more likely to crash.
"Spending a few minutes trying out the simulator should demonstrate to motorists if they need to slow down, and why driving while using a mobile phone or after drinking could well end in tragedy."