Final answer:
The minimum safe following distance in ideal conditions is typically measured by the "3-second rule." In terms of distance, at a speed of 60 km/hr, it would equal approximately 50 meters or roughly 14 car lengths, considering the average car length is 3.5 meters.
Step-by-step explanation:
The minimum safe following distance behind a passenger car in ideal conditions is often quantified by the "3-second rule." This rule states that a driver should stay at least three seconds behind any vehicle that is directly in front of the driver's vehicle. It allows for a safe distance for the driver to react and come to a stop if necessary.
However, the actual distance in meters will vary depending on the car's speed. For example, at 60 km/hr (approximately 16.67 meters per second), a 3-second following distance would be about 50 meters. It is important to note that different driving conditions, such as wet or icy roads, will require greater following distances to ensure safety.
The average length of a car is around 3.5 meters, and it is suggested that in order to cross roads safely in urban areas with a speed limit of 60 km/hr, a pedestrian needs to be able to walk at least 4 meters (considering the car's width of 2 meters plus an additional safety margin) before the car reaches them.
Therefore, in terms of car lengths, the safe following distance in ideal conditions would be roughly 14 car lengths (given that the walking distance required is slightly less than the stopping distance at this speed).