According to AASHTO, what is the recommended K factor percentage for urban areas?

• A. 12 to 18%
• B. 8 to 12%
• C. 5 to 10%
• D. 15 to 20%

Answer: (B)

The recommended K factor percentage for urban areas, according to AASHTO (American Association of State Highway and Transportation Officials), provides guidance for estimating the percentage of daily traffic that occurs during the peak hour. In urban settings, where traffic patterns tend to be more affected by local activities, land use, and travel behavior, the K factor typically falls within the range of 8 to 12%. This range reflects the tendency for urban areas to have a relatively higher percentage of peak-hour traffic as compared to more rural or less densely populated areas.

The K factor is critical for traffic engineering and transportation planning as it helps in designing roadways to accommodate peak-hour traffic volumes effectively. Understanding this percentage allows engineers to make informed decisions regarding lane capacity, signal timing, and overall traffic management strategies in urban environments.

Higher or lower ranges, such as those offered in the other choices, do not align with the urban traffic studies and principles established by AASHTO, which suggests that estimating K factors outside the 8 to 12% range for urban areas may lead to inaccuracies in traffic analyses and transportation planning efforts.