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The downstream ATL length should enable vehicles from a stopped position to reach the desired prevailing speed before reaching the beginning of taper. It should also ensure that adequate gaps exist in the adjacent CTL, particularly at high speeds, to enable safe merge maneuvers before vehicles reach the beginning of taper. Supplemental signs should be applied in advance of the intersection and on mast arms or span wires to indicate that the ATL is intended for use as a through lane and not inadvertently assumed to be a right-turn-only lane. Pavement marking arrows should be considered for application in advance of the downstream merge to provide additional notification to the driver. USER CONSIDERATIONS This section presents considerations for the four primary modes (pedestrians, bicyclists, transit, and auto) and highlights their unique considerations related to the analysis and design of ATLs. Pedestrians Similar to when a CTL is added, when an ATL is added, the distance pedestrians must travel to cross one or more intersection legs is increased. This increased distance produces the following effects: Increased pedestrian exposure to traffic. By increasing crossing distance, ATLs may place pedestrians at higher risk. According to the AASHTO Highway Safety Manual, the greater number of lanes at a signalized intersection, the higher is the likelihood of a vehicle pedestrian crash (4). Reduced pedestrian level of service on side-street approaches. ATLs increase the total crossing distance for pedestrians, resulting in reduced pedestrian comfort and a lower level of service (LOS) for crossing pedestrians, per the Signalized Intersections LOS methodology for pedestrians included in the HCM 2010 (2). Increased minimum pedestrian crossing time. Assuming a typical 12- foot lane and a walk time of 3.5 feet per second, the addition of an ATL will increase the minimum walk time by approximately 3.5 seconds. When pedestrian walk times govern the minimum time a green light is provided to a side-street approach, this effect will increase the proportion of green time provided to the side street approach and reduce the proportion of green time allocated to the main-street approach. To the extent that the increased minimum green contributes to overall pedestrian delay, this will negatively impact pedestrian LOS. Bicyclists Unless a bicycle lane is provided, cyclists should be assumed to use the ATL rather than other through lanes. Many bicyclists may feel uncomfortable in an ATL's merge section due to the "struggle" for available space. If a bicycle lane is available, its location relative to the general traffic lanes may create additional conflict points within a signalized intersection that contains ATLs. Page 11

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For bicyclists on side-street approaches, ATLs increase total crossing distance. This increase will negatively affect bicycle LOS for side-street approaches, according to the Signalized Intersection LOS methodology included in the HCM 2010 (2). Exhibit 2-2 shows potential bicycle treatments with and without exclusive right-turn lanes at signalized intersections. Exhibit 2-2 Bicycle Treatment Examples Transit Bus stops could be located within an ATL on either the near side or the far side of the intersection, depending on transit agency policy, local land uses, and signal timing. Depending on the roadway classification and/or traffic volume, bus stops are sometimes also located within the near-side right-turn lane or in a bus pullout bay on the far side of the intersection. Exhibit 2-3 illustrates potential bus stop locations based on the final configuration of an intersection. Page 12

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Exhibit 2-3 Potential Bus Stop Locations Merging with general traffic can often be difficult for bus operators. In some jurisdictions, it is the law to yield to buses. The Transit Capacity and Quality of Service Manual (TCQSM) provides a method for estimating delay as a result of buses merging into traffic (5). Depending on the guidelines and preferences of the transit agency, and the agency owning the roadway, a right-turn lane may be used as a bus pullout, or a bus pullout could be provided beyond the intersection. Far-side stops often allow buses to take better advantage of the signal progression provided along the roadway, but other considerations such as facilitating transfers to bus routes on cross streets and proximity to transit passenger generators may dictate the use of a near-side stop. If no pullout area is provided, then buses would stop in the outside lane (e.g., the ATL). Motorists typically avoid the outside/auxiliary lane when buses are present, so a high frequency of buses along the street would tend to discourage ATL use. Other observations from the research indicate: For relatively short cycle lengths, near-side bus stops had a limited impact on the intersection operations. Far-side stops within the downstream ATL caused motorist upstream to reposition themselves. Where buses stopped in right-turn lanes (upstream) or bus pullout areas (downstream), they were able to find acceptable gaps to merge back into the traffic stream. Auto Motorists typically seek to minimize delay while traveling through intersections, which means they are likely to consider using the ATL when there is risk of not clearing the intersection in the green phase from the CTL and/or when they can wait in a shorter queue. Page 13

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Certain messages need to be conveyed throughout the ATL to make motorists aware of the ATL and to encourage its use: Prior to the intersection, the driver needs to be made aware of the ATL lane being added. At the intersection, the driver needs to know that the ATL serves through traffic and not just turning movements. After departing the intersection, the driver needs to be made aware of the impending mandatory merge condition. A noted concern from many motorists and highway agency staff members is the use, or misuse, of ATLs by aggressive drivers. Aggressive drivers may choose to use the less-utilized ATL to by-pass vehicles in the CTL. Certain agencies, such as the Maryland State Highway Administration and Connecticut Department of Transportation (6), have experimented with signs indicating an alternating merge area to both encourage use of the ATL by removing the priority of the CTL over the ATL and to encourage courteous behavior. Exhibit 2-4 illustrates some lane-merging signs. Exhibit 2-4 Alternate Merge Sign Examples Page 14