Principles and Guidance for Presenting Active Traffic Management Information to Drivers (2021)

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33 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. On the SR 110 Arroyo Seco Parkway at I-5, dynamic junction control was deployed in 2010 to control access in order to allow a second exiting lane on the connector ramp shoulder during the afternoon peak period, 3-7 PM Monday through Friday. In-pavement lighting was initially installed to show a solid white stripe across the lane when closed but was discontinued use after 2-3 years due to persistent maintenance issues and difficult access for maintenance staff. Overhead signs are fully dynamic, although not full color, and continue operations, as shown in Figure 28. A new project is underway to help manage lane movements with only digital overhead signage and improve compliance. Figure 28. Dynamic junction control on the SR 110 Arroyo Seco Parkway in Los Angeles (FHWA). Minnesota. The I-94 corridor in Minneapolis, where overhead lane use control signage is spaced every half-mile, includes one gantry with an extra-large, full-color DMS instead of individual lane control signs. This DMS is capable of displaying lane control symbols when needed, but instead is often used for dynamic junction control, displaying a guide sign about a downstream exit that designates the outside lane as exit only based on real-time congestion conditions, as shown in Figure 29. Figure 29. Dynamic junction control on I-94 in Minneapolis displaying guide signs for an exit with and without an exit only lane designation (Google Maps).

34 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. A dynamic merge control system for a work zone application may consist of one or more portable DMS in series and placed on one or both sides of the roadway, as seen in Figure 30. As an example, the Florida DOT has used portable DMS for dynamic merge control in work zones and displayed “DO NOT PASS, MERGE HERE” when an early merge was desired, and “STAY IN LANE, MERGE AHEAD” when a late merge was desired. 1 A Minnesota DOT dynamic merge control deployment spaced several portable DMS at one-mile intervals to display “STOPPED TRAFFIC AHEAD, USE BOTH LANES” to encourage a late merge. Minnesota DOT also has used a static sign with flashing beacons to encourage a late merge based on real-time conditions, as seen in Figure 31. Figure 30. Example of a dynamic merge control application encouraging a late merge; top photos show the two-phase message displayed on the first portable DMS and bottom photos show the two-phase message on the portable DMS located at the merge point (International Road Dynamics).2 1 http://www.fdot.gov/research/Completed_Proj/Summary_CN/FDOT_BD548-24_rpt.pdf 2 International Road Dynamics (2005). Dynamic Lane Merge Systems. MdSHA.

35 Figure 31. Dynamic merge control to encourage a late merge at a work zone in Minnesota (Minnesota DOT). Dynamic Queue Warning Deployments As described above in the Multipurpose Overhead Lane Use Control Sign Deployments section, dynamic queue warning is often deployed in conjunction with other ATM strategies in urban areas. However, many states also deploy temporary queue warning systems as a work zone mitigation strategy for improving safety. These systems often use fully dynamic, portable DMS to display messages to drivers depending on current speeds downstream, as depicted in Figure 32. These signs may be spaced at multiple locations upstream from the work zone, depending on expected queue length. Portable DMS may be placed on each side of the road on a multi-lane roadway so 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 cautionary message when speeds drop below a certain threshold, e.g., slow traffic ahead; or • A warning message when speeds are under 25 mph, e.g., slow traffic ahead, be prepared to stop. As an alternative, the Illinois DOT has also used static signs with flashing beacons as a queue warning system, e.g., “Slower traffic ahead when flashing.” Table 7 presents a list of dynamic queue warning systems that have been temporarily deployed in various states. It is likely that additional, similar temporary systems have been deployed in these and other states that are not documented.

36 Table 7. Temporary dynamic queue warning system deployments in the United States. State Dynamic Queue Warning System Descriptions IA As part of the Traffic Critical Projects Program, Iowa DOT routinely uses portable DMS for queue warning systems and speed management in both urban and rural work zones around the state. IL Illinois DOT has deployed numerous queue warning systems on rural freeways for major construction projects, and several Districts have on-call ITS contracts for the provision of queue warning systems on smaller, short-duration construction projects. MI Queue warning systems have been deployed for work zones in Jackson and Ann Arbor on I-94 and south of Detroit on I-275 and I-75 for a third project. MN Minnesota is testing a dynamic zipper merge including some queue warnings using portable dynamic message sign in a work zone on US 52. Additionally, a couple recent projects on I-35 utilized a dynamic queue warning system with static signs and flashers. SD To manage high special event traffic volumes during the Sturgis Motorcycle Rally, an advanced queue detection system has been used to help warn motorists of stopped traffic on I-90. TX A queue warning system was deployed on I-35 to reduce the risk of crashes on a project in central Texas. The system included a portable work zone queue detection and warning system combined with portable rumble strips. WA Work zone projects at Snoqualmie Pass on I-90 sometimes use a shadow vehicle with a mounted dynamic message sign as a queue warning system to provide motorists with advanced warning of slowed or stopped traffic. Figure 32. Typical, temporary dynamic queue warning system deployed for a work zone on I-35 in central Texas (Texas A&M Transportation Institute). Static Signage in Advance of ATM Deployments Because ATM deployments are relatively new to drivers in many parts of the United States, deploying agencies frequently take extra steps to facilitate driver understanding of the displays and symbols being used. In some cases, this may be a legal requirement that is mandated by the legislature, for example, as a condition for enforcement purposes or deploying a new strategy such as dynamic speed limits or a dynamic shoulder lane that is a change from current practices. Still, an often cited challenge and source of driver feedback to agencies is conveying the meaning of what the dynamic sign is displaying. For example, driver feedback in Seattle included confusion over whether the dynamic speed limit display was a feedback sign intended to convey an individual’s speed or the speed of traffic ahead, when it is intended as a regulatory

37 speed limit; there was also driver confusion when the dynamic speed limit displayed was higher than congestion levels during stopped traffic. Agencies commonly conduct a public information campaign with local media before beginning a new type of ATM strategy in a region. Another approach is to add text, if possible, above or below the symbols displayed on lane control signage, such as “merge” or “closed” to convey the meaning of the symbols. Many ATM deployments post static signage in advance of the deployment to advise drivers. For a regulatory dynamic speed limit, some states may legally require a sign that alerts drivers that they are entering a dynamic speed zone for enforcement purposes. In other cases, a static sign may be placed in advance of a dynamic speed zone simply for informational purposes. A common example is a sign with text “variable speed zone ahead,” as used in Seattle, as seen in Figure 33, and one option for Utah DOT when using dynamic speed limits in work zones. Alternative examples are shown in Figure 34 in advance of a temporary dynamic speed limit for a work zone on the I-495 Capital Beltway in Virgnia, in Figure 35 for dynamic speed limits that have since been removed from I-270 in Missouri. These static signs may be accompanied by other features to grab driver attention, such as flags, as seen in Figure 33 for Seattle, or a flashing beacon that activates when there is a reduced speed limit, as seen in Figure 36 for US 27 in Florida. Figure 33. Static sign in advance of dynamic speed limits on SR 520 in Seattle (Google). Figure 34. Static sign in advance of temporary dynamic speed limits in a work zone on I-495 in Virginia (Virginia DOT).

38 Figure 35. Static sign in advance of dynamic speed limits on I-270 in St. Louis (AAroads.com) Figure 36. Static sign in advance of dynamic speed limits on US 27 in Fort Lauderdale (AAroads.com) Dynamic shoulder lanes or lane control signage may also include static signage to advise drivers about the meaning of the symbols. The static signage used on the former dynamic shoulder lane deployment on I-66 in Northern Virginia was placed over the lane control sign on certain gantries to explain the symbols, and complemented by other roadside signs to present the hours of operation, as depicted in Figure 37. After lane control signs were placed over every lane on I- 66, the static roadside signs were updated, as seen in Figure 38. A similar overhead sign is used in advance of the dynamic shoulder on I-495 in Virginia, depicted in Figure 39, as well as a similar roadside sign used on I-85 in Georgia, shown in Figure 40. Figure 37. Static sign to explain former dynamic shoulder lane symbols and hours on I-66 in Northern Virginia (FHWA). Figure 38. Static sign to explain lane control symbols currently in use on I-66 in Northern Virginia (Virginia DOT).