What is the recommended driver eye height for roadway design?

The recommended driver eye height for roadway design is 3.5 feet. This standard is based on the average driver characteristics and reflects a typical seated eye height. Using this measurement is crucial for ensuring that horizontal and vertical alignments of roadways, as well as sight distance considerations, are designed to enhance safety and visibility for the majority of drivers.

Designing roadways with a driver eye height of 3.5 feet helps to make accurate predictions about how drivers will interact with the road environment, including their visibility of signs, other vehicles, and any potential hazards. This standard height facilitates effective designs for sight distances, which are essential for safe stopping and navigating road curves.

In terms of practical application, using a height significantly lower than 3.5 feet may lead to overestimating visibility and potentially compromising safety, while choosing a height much higher could restrict sight distance calculations, leading to unsafe designs. Hence, adopting 3.5 feet allows for a balanced and realistic approach in roadway design, meeting the needs of a majority of the driving population.