According to AASHTO guidelines, which tables are referenced for determining when a left turn (bay) lane is warranted?

• A. Tables 9-22, 9-23
• B. Tables 9-24, 9-26
• C. Tables 9-24, 9-25, 9-26
• D. Tables 9-20, 9-21

Answer: (C)

The correct answer identifies Tables 9-24, 9-25, and 9-26 as the reference points in the AASHTO guidelines for determining when a left turn lane is warranted. These tables provide critical information regarding the various conditions under which a left turn lane should be considered necessary based on traffic volume, types of turning movements, and other influencing factors such as accident history and the nature of adjacent land use.

Table 9-24 specifically outlines the minimum volumes for left-turn movements that warrant the installation of a left turn lane. This table helps transportation engineers assess traffic patterns and decide whether a dedicated lane is necessary for safe turning.

Table 9-25 focuses on the warranting criteria that include considerations such as the left turn volume in relation to opposing traffic.

Table 9-26 discusses additional factors like the operational characteristics of left turns at intersections and the benefits of dedicated lanes in reducing the conflict between turning and through traffic.

Together, these tables form a comprehensive guideline ensuring that left turn lanes are only provided when the traffic conditions justify their need, thereby enhancing safety and efficiency at intersections.