What is the formula represented as 1.47V*t + V²/[ 30[[a/32.2] ±G] used for?

The formula 1.47V*t + V²/[30[[a/32.2] ±G] is used for determining stopping sight distance (SSD), which is a critical parameter for highway design and safety. Stopping sight distance is the total distance a vehicle travels from the moment the driver perceives a need to stop until the vehicle comes to a complete stop.

In this formula, V represents the speed of the vehicle, t is the perception-reaction time, a is the acceleration due to braking, and G is the grade of the road. The first term (1.47V*t) accounts for the distance traveled during the perception-reaction phase, while the second term (V²/[30[[a/32.2] ±G]) accounts for the distance required to come to a complete stop under the influence of braking and road grade.

Given the significance of SSD in ensuring that drivers have adequate visibility and reaction time to stop safely before an obstacle, this formula is essential in roadway design, where safety and efficiency are paramount. Properly calculating SSD helps engineers design roads that reduce the likelihood of accidents and enhance overall traffic safety.