Access Management in the Vicinity of Interchanges, Volume 1: Practitioner’s Guide (2022) / Chapter Skim
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Pages 17-35
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17 Corridor Characteristics The variety of interchange functional forms described in Chapter 2 substantially influences the crossroad operational and safety performance. In addition to the type of interchange, a variety of corridor characteristics also influences crossroad performance.
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18 Access Management in the Vicinity of Interchanges for on- and off-ramps that are spaced at distances that do not match the spacing of the signalized intersections in the corridor complicates attempts to achieve good progression. Traditional diamonds and PARCLOs typically have spacing that does not match nearby signalized intersection spacing.
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Corridor Characteristics 19 Cycle Length (seconds) 1/4-Mile Spacing Speed (mph)
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20 Access Management in the Vicinity of Interchanges Where the spacing between signalized intersections is not uniform, some coordination and progression can still be achieved. Reasonable alternatives include the following: • Time the signals to provide maximum progression in the direction of the largest demand during the peak period.
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Corridor Characteristics 21 New Mexico DOT has similar warrants structured differently based on hourly RTV, speed, and minimum hourly volume in the adjacent through lane (3)
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22 Access Management in the Vicinity of Interchanges treatment is justified on two-lane rural roads. This is based on cost-benefit analysis for unsignalized intersections with only a left-turn lane peak-hour volume of five vehicles and 150 vehicles per hour per lane (vphpl)
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Corridor Characteristics 23 the intersection still has legal pedestrian crosswalks, and signal timing must still be provided for pedestrians. Longer cycle times result from the longer phase times to accommodate pedestrians.
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24 Access Management in the Vicinity of Interchanges intended use more effectively. In addition, lane turn arrows placed in the lane clearly convey to the drivers how the lanes are to be used.
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Corridor Characteristics 25 whether the road is public or private and the type of land uses served. It is also beneficial to define if there is inter-parcel circulation, street service to the back of parcels, and reasonable alternative access to the properties.
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26 Access Management in the Vicinity of Interchanges Green Book recommends a median width of 20 ft or more (10)
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Corridor Characteristics 27 The primary determinants for the number of lanes are the expected traffic demand for each lane and the number of vehicles targeting the same destination (such as the right-turn at the downstream intersection)
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28 Access Management in the Vicinity of Interchanges The peak conditions have lower speeds, shorter maneuver times, and longer queues. The off-peak period has higher speeds, longer maneuver times, and shorter queues.
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Corridor Characteristics 29 • Traffic volume, • Number of lanes including turn lanes, • Median type and configuration, • Safe access and circulation schematics and/or aerial photographs, and • Provisions for bicycle, pedestrian, and transit users. 3.6 Access Point Characteristics In many cases, access can be provided safely and efficiently; however, the unique characteristics of each access point should be considered to better understand potential limitations.
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30 Access Management in the Vicinity of Interchanges • Queue storage, and • Section of roadway with no access upstream from the beginning of the point at which perceptionreaction is initiated. Where access within the upstream corner clearance distance cannot be avoided, a non- traversable median can be used to restrict driveway movements to right-in, right-out activities only.
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Corridor Characteristics 31 • Right-in, right-out only access. • Left-in, right-in, right-out only access.
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32 Access Management in the Vicinity of Interchanges • Increased intersection capacity and reduced intersection delay due to reducing pedestrian signal phases at the nearby intersection. Optimally, the signalized, mid-block pedestrian crossing should incorporate a raised median that provides pedestrian refuge.
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Corridor Characteristics 33 segments; however, property abutting the crossroad close to an interchange is often developed into commercial uses on parcels with small frontages. The result is a high ingress and egress volume on a short roadway segment adjacent to the interchange.
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34 Access Management in the Vicinity of Interchanges 3.9 Land-Use Implications 3.9.1 Key Land-Use Considerations An interchange with a major crossroad creates a "magnet" for development. In rural areas and the suburban fringe, highway-oriented businesses such as restaurants, service stations, motels, and truck stops are common.
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Corridor Characteristics 35 • Current land development policies and standards or guidelines, • Driveway volumes entering and exiting values for peak hours and 24 hours by vehicle type, • Pedestrian volumes parallel to and crossing the roadway by location and time of day, • In addition, the following information/documents need to be developed and adjusted: – Interagency agreement identifying the responsibilities of the state DOT and each local agency, and – A comprehensive plan for development and/or redevelopment of the interchange area. 3.10 References 1.
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