While there are plenty more places with traffic issues in the DMV (D.C., Maryland, Virginia), the National Capital Region Transportation Planning Board has released its top ten bottleneck analysis in its report for the calendar year of 2021 (seen below). According to the report, bottlenecks are typically defined by a traffic queue upstream of the bottleneck, a beginning point for a queue, free flow traffic conditions downstream of the bottleneck that have returned to nominal or design conditions, a predictable recurring cause, and traffic volumes that exceed the capability of the confluence to process traffic.
The PDA Suite Bottleneck Tool offers several bottleneck ranking factors using tool-specific methodology:
• Base Impact (queue length and duration)–judged to be most consistent with TPB’s prior (consultant) aerial photography-based analyses; emphasizes major roadways
• Congestion (queue length and speed drop)–inclusion of speed drop may increase emphasis on smaller roadways
• Total Delay (speed drop weighted by traffic volume)–the database’s traffic volumes seem inconsistently derived, and are often a temporal mismatch (e.g., using 2019 volumes to weight 2010 conditions)
• Based on staff sensitivity tests, ranking by“base impact” produces results that are logical and the most consistent with other TPB work