BACKGROUND: In September 2018, the American Association of State Highway and Transportation Officials (AASHTO) published the 7th edition of A Policy on Geometric Design of Highways and Streets (also known as the 2018 Green Book). The 2018 Green Book provides guidance for determining geometric design criteria of roadways, including guidance on acceleration/deceleration and stopping sight distance criteria. Acceleration/deceleration is influenced by many factors (e.g., grade, vehicle type, and maneuver type). Stopping sight distance is influenced by many factors (e.g., perception reaction time, object height, and driver’s eye height). In addition, the recent changes in vehicle fleet, vehicle technology, and driver population impact the design criteria. Research is needed to identify the limitations of the 2018 Green Book guidelines for acceleration/deceleration and stopping sight distance criteria, develop improved guidelines, and recommend changes to the 2018 Green Book for consideration and adoption by AASHTO. Improved guidance could result in reduced environmental impacts, savings in construction costs, and reductions in construction time.
OBJECTIVE: The objective of this research is to update the guidelines for acceleration/deceleration and stopping sight distance criteria contained in the 2018 Green Book.
Status: Research is complete; has been published as NCHRP Research Report 1081, available at https://nap.nationalacademies.org/login.php?action=guest&record_id=27490
The appendices are available at
https://onlinepubs.trb.org/onlinepubs/nchrp/15-75/15-75_Appendices_to_Final_Report.pdf
