Guidelines for Implementing Managed Lanes (2016) / Chapter Skim
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3 Introduction to Managed Lanes Overview Subject Context Managed lanes in the context of these guidelines are designated (also defined as preferential) lanes and roadway facilities located on or adjacent to controlled-access urban/suburban metropolitan highways that are actively operated and managed to preserve operational performance over comparable general traffic lanes.
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4thus improving the roadway's ability to move more people in fewer vehicles. The following definition for HOV lanes is from NCHRP Report 414: HOV Systems Manual (3)
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5 the American Association of State Highway and Transportation Officials (AASHTO)
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6may be created to expand the range of managed lane facility types and applications. Locally Recognized Terms Some local and state agencies have used other terms from time to time to substitute for the generally recognized types of facilities described previously.
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7 Attributes Critical to the Success of Managed Lanes There are implicit conditions that should exist for managed lanes to be considered viable. These include the following: • Recurring congestion (level of service [LOS]
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8The Federal Role Federal policy and funding legislation have played an important role in the managed lane evolution up through the most recent priced managed lane projects that have opened. Selected events that appear to have the most significant impact on this evolution include the following: • Federal Clean Air Act, as amended, that set the stage for air quality monitoring, mitigation plans for areas meeting nonattainment, and use of Congestion Mitigation and Air Quality (CMAQ)
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9 ing HOV lanes through variable pricing (e.g., allowing solo vehicles to pay a toll while allowing HOVs to travel free or at a discount)
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10 • Need to manage at least some roadway capacity in perpetuity. • Need to increase access controls.
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11 rience over the past 40 years suggests that reaching this determination involves simultaneous attention to both design and operation needs and is iterative successively through some, and perhaps many, stages of concept screening, refinement, and project development. This process will be addressed in more detail in Chapter 2 (planning)
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12 most widely applied concept. The popularity of this concept is due to the symmetrical layout of urban freeways with a center barrier, center-oriented bridge columns, and sign gantry columns; the availability of median shoulders, which are often converted to travel lanes; and a direction split in travel demand that is often balanced.
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13 and the other direction in the afternoon. Permanent concrete barriers separate these lanes to prevent oncoming traffic conflicts.
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14 Queue Bypass A short, dedicated lane may be implemented around a pointspecific traffic bottleneck. This bottleneck may be operational or geometric in nature.
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15 ity regulatory signage. After the advent of electronic toll collection, pricing became a demonstrated and adopted strategy that continues to gain interest and practice.
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16 Access Control Some practitioners may consider the first managed lanes to have been express lanes incorporated into controlledaccess urban roadways in the late 1950s and early 1960s. Such projects as the I-70 Daniel Boone Expressway in St.
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17 ing to prioritize operation for users. This type of tolling offers an opportunity to manage a preferential lane or roadway in real time as capacity allows.
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18 to complement the respective HOV or express lane operation. Tools employed include dynamic advisory speed limits (e.g., in Minnesota; see Figure 27)
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19 prior to opening; costs that were difficult to predict for longterm dedicated operation, enforcement, and maintenance; and regular performance monitoring to address changing traffic and demand conditions. Planning decisions were often the result of opportunities based on either funding or policy, or resulted from a program to rehabilitate or rebuild a corridor.
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20 facility. Common types of crashes within a facility include the following: • Rear-end crashes due to congestion.
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21 similar frequency of crashes as the continuous-access lanes; however, the crashes were concentrated at the access points. Driver Expectancy Driver expectancy reflects the driver's readiness to respond to situations, events, and information in predictable and successful ways (26)
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22 The guide consists of six chapters that generally frame the topic areas applied to project implementation. To properly address the close synergies between design, traffic control devices, operation, and implementation, the reader is encouraged to explore these topic areas in tandem because each is heavily influenced by the others in the iterations required to reach consensus on a best approach for a particular project.
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