Principles and Guidance for Presenting Active Traffic Management Information to Drivers (2021) / Chapter Skim
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3 Chapter 2: State of the Practice A variety of ATM systems has been deployed in the United States and internationally. This section first presents guidance from the Manual of Uniform Traffic Control Devices (MUTCD)
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4 Use of these symbols are generally consistent on ATM lane use signage in the United States, although some locations use text instead of a yellow X to indicate a lane is closed ahead, as shown in Figure 2. To minimize driver confusion, some locations also display text to accompany symbols.
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5 advisory speed sign that might be placed at a curve, for example. Figure 2 and Figure 3 show variations in how advisory speeds are displayed to drivers on dynamic signs.
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6 • Larger dynamic message signs (DMS) are often on the gantries to display an additional text message, however, the size and position of DMS on the gantry vary, as well as the spacing.
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7 Table 1. Overhead dynamic lane control signage deployments and accompanying strategies in the United States.
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8 Colorado. Features of the Colorado DOT lane use control systems on I-25 south and US 36 in the Denver area include: • Gantries on corridors in Denver have a mix of providing zero, one, or two medium-sized DMS on the side(s)
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9 Figure 6. Lane use control signage on the I-295 Delaware Memorial Bridge (Google Maps)
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10 Minnesota. Features of the Minnesota DOT lane use control systems on I-35W and I-94 in the Minneapolis-St.
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11 • When the shoulder is closed, a red X is displayed over that lane, as seen in Figure 11, except at on-ramps where a diagonal yellow arrow is displayed under the text "merge." • Gantries do not include other static signage, as seen in Figure 11 and Figure 12. • Additional gantries with a single lane control sign are provided at intermediate distances as necessary to help support dynamic shoulder operations.
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12 • Gantries on corridors in Seattle have a mix of providing one or two medium-sized DMS on the side(s) of the gantry at a slightly lower level than the signs over the lane, as shown in Figure 13, based on the number of lanes on the highway; one large DMS on the right side of the gantry, as shown in Figure 14; or no supplemental DMS in some locations.
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13 Dynamic Lane Control and Dynamic Lane Reversal Lane control deployments exist in many locations to serve both arterial and freeway applications of lane reversal. However, most of these deployments operate on a static time-of-day basis, rather than dynamic, real-time congestion conditions.
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14 Figure 17. Lane reversal deployment on I-595 HOT Lanes in Miami (Google Maps)
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15 Table 2. Current and planned dynamic shoulder lane deployments in the United States.
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16 was initially installed with in-pavement lighting at the beginning of the segment, as seen in Figure 21; however, this was subsequently removed due to recurring maintenance issues. Dynamic shoulder lane usage will be suspended on this segment following a highway widening project that will begin in 2018.
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17 lane control signs, and managed lane signage. Additional gantries with a single lane control sign supplement the larger gantries to specifically support dynamic shoulder lane operations where needed, as shown in Figure 23.
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18 Figure 25. Dynamic shoulder lane on I-495 North in Northern Virginia (Google Maps)
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19 One additional item to note is the variations in how states provide information to drivers via supplemental DMS or dynamic elements on the dynamic speed limit signs to provide explanation for the reduced speed. For example, as depicted below in Table 5, an Oregon deployment on I-84 and a Washington deployment on I-90 at Snoqualmie Pass display a speed limit sign graphic on the left side of a full-size DMS and can provides text on the right side, e.g., "low visibility." Similarly, dynamic speed limit signs in Tennessee on I-75 includes a dynamic element that displays "fog." Supplemental medium- or full-sized DMS located in advance of or on the same gantry as dynamic speed limit signs can also provide explanation to drivers to justify and encourage travel at reduced speeds.
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20 Table 3. Current, planned, and discontinued dynamic speed limit deployments in the United States.
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21 State and Route(s) Type Purpose Sign Location Sign Type W ith S ig ns F or O th er A TM S tr at eg ies System Location and Other Details R eg ul at or y A dv iso ry C on ge st io n W ea th er W or k Zo ne O th er R oa ds id e O ve rh ea d Fu lly D yn am ic D yn am ic D ig its OH: US 33, I-270 x x x x Includes flashing beacon.
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22 State and Route(s) Type Purpose Sign Location Sign Type W ith S ig ns F or O th er A TM S tr at eg ies System Location and Other Details R eg ul at or y A dv iso ry C on ge st io n W ea th er W or k Zo ne O th er R oa ds id e O ve rh ea d Fu lly D yn am ic D yn am ic D ig its NV: I-15, I-515, US 95, US 93 x x x x x Under construction: In Las Vegas.
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23 Table 4. Urban and congestion dynamic speed limit deployments in the United States.
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24 NJ: I-78 New Jersey Turnpike (FHWA) OR: SR 217 –left (Oregon DOT)
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25 Table 5. Weather dynamic speed limit deployments in the United States.
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26 Table 6. Select dynamic speed limit deployments in work zones.
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27 Dynamic Junction Control Deployments In addition to the related practice presented above that is used in Seattle to caution drivers in the outside lane of heavy traffic at a downstream off-ramp and use of merge symbols on dynamic shoulder lane control signs at on-ramps when the shoulder is closed, there are two other examples of dynamic junction control that are presented here. California.
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28 Dynamic Merge Control Deployments A number of states have used dynamic merge control in work zone applications. In situations where one or more lanes is closed on a multi-lane roadway due to work zone activity, there are mobility and safety considerations for encouraging drivers to merge early or late, depending on the circumstances.
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29 drivers will see the message even if there is a large truck obstructing the view; in this case, the Illinois DOT requires the sign displays to be synchronized, but since this is difficult to control the signs are staggered 500 feet apart so they are not directly side by side, which could confuse drivers trying to read both signs. As an example of messages displayed, Illinois DOT typically uses the system-provided recommendations, posting one of three messages on the signs based on real-time speeds downstream: • An advisory message if there is no congestion, e.g., left lane closed ahead, use caution; • A caution message when speeds drop below a certain threshold, e.g., slow traffic ahead; • A warning message when speeds are under 25 mph, e.g., slow traffic ahead, be prepared to stop.
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30 Figure 29. Typical, temporary dynamic queue warning system deployed for a work zone on I-35 in central Texas (Texas A&M Transportation Institute)
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31 Figure 30. Static sign in advance of dynamic speed limits on SR 520 in Seattle (Google Maps)
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32 Figure 34. Static sign to explain dynamic shoulder lane symbols on I-495 in Northern Virginia (Google Maps)
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33 As with deployments in the United States, many variations exist among international deployments in how information is presented to drivers. • ATM signs may be separate or in conjunction with other static signage; • Australia presents a static sign to clarify a default speed limit when ATM signs are blank; • Some countries like Australia and New Zealand have flashing beacons adjacent to dynamic speed limit signs; • Some countries like the Netherlands use rotating drums with static images to convey information; • Some countries, including the Netherlands, Spain, and the United Kingdom use automated enforcement with dynamic speed limits to increase compliance, and may include static signs to convey the presence of speed cameras to drivers; • The United Kingdom has deployed pictogram displays on DMS to convey information about lane closures, instead of a sign over each lane, as seen in Figure 36.7 This practice is being considered as an alternative to signs over every lane in future Minnesota deployments.
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34 true example of in-vehicle ATM messaging, it is worth noting as a first step for states that are beginning to consider in-vehicle messaging that is possible with new technologies and a precursor to the connected vehicle environment. As research progresses and the reliability of these types of dynamic notifications is confirmed, enhancements may allow these types of notifications to become more advanced toward true in-vehicle ATM messaging.
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35 Figure 37. In-vehicle display for INCZONE dynamic merge control and dynamic speed limit applications during closed field test demonstration in Maryland (Battelle)
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