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ATL APPLICATION EXAMPLE DESCRIPTION The study intersection for this example is located at the crossroads of a principal arterial and a minor arterial in a suburban setting. Exhibit 6-2 identifies the key characteristics of the two roadways. Characteristics Major-Street Roadway Minor-Street Roadway Exhibit 6-2 Sample Application Roadway Classification Principal Arterial Minor Arterial Characteristics Avg. Annual Daily Traffic 25,000 15,000 Posted Speed 45 mph 35 mph Lane Configuration 1 shared through/right lane 1 shared through/right lane 1 through-only lane 1 left-turn lane 1 left-turn lane The local highway agency has received a significant number of complaints from citizens about back-ups on the eastbound approach at the intersection and future volume forecasts show additional traffic growth on the approach will only continue to degrade its operational performance. Options for adjusting the signal timing are very limited due to the high volume of traffic on the principal arterial and the intersection's location on a coordinated arterial. The local highway agency is evaluating options for relieving the congestion on the eastbound approach. The minimum acceptable level of service for the design year is LOS E with a requirement that the volume-to-capacity ratio for all lane groups be less than 1.0 for the peak-hour period. An arterial capacity analysis shows there is sufficient downstream capacity on the minor arterial to accommodate up to a 50 percent increase in through volume. However, because of right-of-way and funding constraints, the local highway agency has ruled out certain capacity-enhancing solutions such as adding a second CTL, converting to an alternative intersection configuration, or constructing dual left-turn lanes on the approach. The volume-based data shown throughout this example represent the forecast demand on the eastbound approach, and not necessarily the volume measured through the intersection. This distinction is important as the final alternative selected should provide enough capacity to accommodate the full demand on the approach and not just the volume currently able to pass through the intersection. The term "volume-to-capacity ratio" will continue to be used, as it is the industry standard term for the performance measure of the volume or demand to the capacity of a movement, approach, or intersection. The local highway agency is evaluating several improvement alternatives for the minor arterial eastbound approach: Alternative 0: Base case (do nothing) Alternative 1: Add an exclusive right-turn lane Alternative 2: Add a shared ATL Alternative 3: Add an ATL and an exclusive right-turn lane The practitioner must be aware that these improvement alternatives are not the only alternatives that could be applied to address the congestion issue; Page 57