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WSDOT Design Manual, Chapter Shared-Use Paths - DocsLib.Wsdot design manual
The purpose of the Highway-Rail Crossing Handbook, 3rd Edition is an information resource developed to provide a unified reference document on prevalent and best practices as well as adopted standards relative to highway-rail grade crossings. Follow Us:. About the Author. The enforcement area should be located on the right side for queue bypasses and downstream from the stop bar so that the officer can be an effective deterrent.
The overall length of the enforcement area may be adjusted to fit the specific conditions on the ramp. Freeway-to-Freeway Metering Freeway-to-freeway metering consists of metering a ramp that connects one freeway to another. It is critical in this high-speed environment that adequate sight distance and sufficient advance warning be provided to motorists, as they will likely not be expecting to stop. Figure shows an example of freeway-to-freeway metering in Portland, Oregon.
Another example of this application is in San Diego, California, where its first use was in Since then, three more installations have been constructed. One application was implemented in to relieve congestion and queuing through the interchange. All three lanes on the ramp are metered two general-purpose lanes plus an HOV lane. Caltrans believes that this is due to the high level of service provided on the freeway and, in particular, the high speeds that are maintained beyond the meters.
Travel time savings are estimated to be up to 20 minutes for certain home-to-work commute trips. Some suggested policies for the use of freeway-to-freeway ramp metering, as outlined by WSDOT, include: [ 16 ]. Ramp meter hardware consists of a ramp controller, signal heads, signal pole s , and detection devices.
Ramp Controller The controller assembly consists of a cabinet, controller, load switches, input files, loop amplifiers, and other devices similar to a traffic signal at an intersection. The ramp controller typically acts as a data station as well as a signal controller. The most common ramp controllers are type s or type s. The s are microprocessor-based devices that control the ramp meter signals using information from the loop detectors. The s provide similar functions to the type s and are more powerful VME-based Versa Module Eurocard controllers with bit microprocessors that provide additional functionality to the older s.
Figure shows the back-top view of a V unit with an additional 7a card installed and the top cover of chassis removed. Other necessary features include the ability to provide accessible power source and communication with the TMC. Communication can be provided via telephone lines, fiberoptics, microwave, or radio frequencies RF.
Figure : Type V Controller [ 17 ]. Signals For single-lane ramps, a Type I signal pole vertical pole only with two signal heads should be located on the left side of the ramp, adjacent to the stop line. For two-lane ramps, a Type I signal pole can be located on each side of the ramp or a mast arm-style signal pole with overhead signal heads can be used. For three-lane ramp meters, a mast arm signal pole should be used.
An FHWA official interpretation of this section of the manual dated September 30, recommends that for multi-lane metering where staggered or independent release is used, two signal heads per lane should be used. The yellow phase is the transition between green and red and at signal start-up. For operational efficiency, it works best to cycle from red to green during the operational cycle, with no yellow phase. However, practitioners should verify that a yellow phase is not required by local or state law.
A yellow phase should be used at start-up to alert motorists that the ramp meter will be activated and begin to meter traffic. Figure shows an example of where the signal heads should be mounted for a three-lane ramp where the HOV lane is metered. If the HOV is not metered, then only two signal heads should be used. Detectors Several detectors are required to operate ramp signals.
Detection has traditionally been implemented in the form of induction loops. However, other detection devices could be used if more suitable to the agency and the environment. For example, Atlanta installed video detection VIDS on freeway mainlines to avoid closures and hazards related to installing loops on an operating freeway. The detector locations are related to the detector functions. The functions include: demand, passage, ramp queue, mainline, exit ramp, and entrance ramp without metering.
Figure through Figure show typical ramp metering detector loop layouts used by Caltrans. Demand Detectors Demand detectors are installed in each metered ramp lane, just in advance of the stop bar. The demand detection zone provides coverage in the area just upstream of the stop bar, and operates as a typical traffic signal stop-bar detection zone. Figure shows a typical layout for passage and demand detectors on a single-lane ramp while Figure shows a typical layout for a two-lane ramp.
Passage Detectors Passage detectors are installed immediately downstream of the stop bar. The passage detection zone provides coverage downstream of the stop bar in each metered lane. Passage loops are used to count the number of vehicles that enter the freeway.
This information can be used to determine the duration of the green signal display. Figure shows a typical layout of passage and demand detectors for a three-lane configuration with a non-metered HOV lane. Ramp Queue Detectors Ramp queue detectors are installed near the intersection of the ramp with the adjacent surface street.
Intermediate queue detectors may be added to the ramp as well. These intermediate detectors help identify when the queues are beginning to fill the ramp capacity. Ramp queue detectors monitor excessive queues that cannot be contained within the queue storage area, and they provide input to maximize the metering discharge rate to clear excessive queues.
This helps prevent queues from spilling onto the local streets and disrupting arterial operations. Mainline Detectors Several mainline detection zones are required for ramp meter operations. In isolated operations, the mainline detection zone is located upstream of the entrance ramp gore point see Figure These detectors can also provide data for centralized ramp metering and incident detection algorithms.
Figure shows a typical layout for mainline detectors as used by Caltrans. Exit Ramp Detectors Exit ramp or off-ramp detector loops may be installed for traffic count information. For many system-wide, traffic-responsive meter algorithms, exit ramp detection is either highly desirable or required.
Figure shows a typical layout for exit ramp detectors as used by Caltrans. Entrance Ramp Detectors for Ramps without Meters For system-wide, traffic-responsive ramp meters, detection is important on entrance ramps that are not metered. Accurate corridor count data ensures that the proper metering rates are implemented at the metered ramps. Data from these detectors can also be used for a variety of other applications, including performance monitoring and planning. The potential for motorist confusion increases as the metering layout becomes more complex i.
In addition, not all motorists are familiar with ramp metering operations. Thus, the signing and pavement markings for ramp metering must be as clear as possible. Table provides a description of where each sign is typically located and its specific application. Placed on the arterial approximately 61 meters feet upstream of the ramp entrance point. The sign should generally be placed on the right side of the arterial.
This warning sign is accompanied by a yellow flashing beacon that is activated during metered periods to alert motorists of the upcoming controlled ramp. Positioned near the beginning of the dual-lane queue storage reservoir on the right side of the on-ramp or positioned on both sides of the ramp.
This regulatory sign is used to convert the single lane on-ramp into a dual-lane queue storage reservoir during ramp meter operations. Placed on both sides of the on-ramp at the signal stop bar. This sign is placed on the signal pole under the post-mounted configuration.
This regulatory sign identifies the signal stop bar location and is used to align drivers over the demand detectors placed upstream of the stop bar. This regulatory sign is used to inform motorists of the intended traffic control method under ramp metering operations.
This regulatory sign is used when converting a non-metered HOV bypass lane to a metered operation. Also may be used on new installations where potential for confusion exists. This warning sign is used to inform motorists that a traffic signal is ahead and to be prepared for the potential to stop.
Placed approximately This warning sign is used to inform motorists of the need to merge with another ramp lane prior to entering the freeway mainline. Warning motorists of the metered operation is important because motorists do not expect to stop on ramps. This is especially true for freeway-to-freeway metering applications.
Advance warning signs are recommended in advance of all metered ramps. There are different types of warning signs that can be used. These signs may be internally illuminated or accompanied by flashing beacons to draw attention. Figure shows an example of an extinguishable message sign for a freeway-to-freeway ramp metering application. High visibility is a crucial requirement for these signs because motorists do not expect to stop on the freeway. Caltrans recommends installing these signs at least 30 meters Caltrans recommends installing these signs at least to meters See Figure for a typical layout.
Pavement Markings Pavement markings usually consist of either paint, plastic, or raised pavement markers. Stop lines should be placed at a location that balances the acceleration and taper length needed downstream of the meter with the queue storage needed upstream of the meter.
It is not advised to provide staggered stop lines. Lane lines are needed to separate the metered lanes. There also may be HOV lane markings, which are discussed in the following subsection. When use of the shoulder is permitted during ramp metering, the shoulder should be marked with a stop bar. The standard HOV lane pavement marking is the elongated diamond symbol shown in Figure Solid white lines separating the HOV lane from the general-purpose lanes and dashed extension lines are applied to prevent turning vehicles from entering the HOV lane.
Signing that provides HOV information signs may also be installed. Figure shows a sample HOV sign. Figure shows another sample of an HOV sign that can be used to designate the preferential treatment. There are several design considerations to address when providing for ramp closures. Equipment, as well as signing and pavement markings, is required for ramp closures.
As discussed in Chapter 5, there are three general types or classifications of ramp closures: permanent, temporary, and time-of-day. This section discusses the design considerations for each of these types of closures, provides some sample ramp closure layouts, and explains the various types of devices that can be used for ramp closures. The decision to close a ramp permanently can be a very lengthy process. The many requirements include a detailed traffic analysis to show impacts associated with the closure; an extensive public outreach process to make sure that citizens are informed of the potential change and have an opportunity to provide input; and perhaps a temporary closure to observe and experience the actual impacts before a final decision is made.
Extensive traffic analysis was required, and an open house was held to present the findings to the public and obtain their comments and concerns. Since the impacts were not significant, the decision was made to permanently close the on-ramp. Temporary closures may be implemented due to construction activities, special events or weather-related events.
Mitigation needed for a temporary closure is usually not as extensive as for a permanent closure, but the public outreach effort may be just as extensive. Although the disruption may only be temporary, it still has the potential to have severe impacts for users of the ramp. Ramp closures that occur only at times of low traffic demand like night-time hours will have less impact on travelers and may have less severe impacts overall, so the outreach effort will not need to be as extensive as for closures that affect peak traffic hours.
Construction impacts in work zones are also a design consideration for temporary closures. An example of a temporary ramp closure is the 6th Street ramp of I in St.
Louis, Missouri, which was closed for a two-year period. Louis Cardinals baseball team. In addition to advance information for motorists who intend to use the ramp, information on the alternative route needs to be provided.
Alternative route information may be posted on Changeable Message Signs CMSs on arterial streets near the ramp entrances. An example of a special event temporary closure is the Tacoma Dome in Washington State, which has required ramp closures in the past.
During any major Dome event, Exit the exit nearest the Dome used to back up onto the freeway. Since these queues were quite extensive and the ramp lacked the capacity to store the vehicles, this exit was closed using barricades and DMS to warn motorists.
Information was also sent to the Dome patrons along with their tickets as a reminder of the freeway ramp closure. Closing the ramp during major special events was successful in eliminating queuing back to the mainline. Gates on the mainline direct traffic off the Interstate and gates at entrance ramps prohibit access. Like temporary closures, time-of-day closures also have the same design considerations with respect to traffic analysis, public outreach and trial closures, except that these types of closures are typically focused on the morning or afternoon peak periods.
These types of closures can be used to help to facilitate mainline flow or reduce the occurrence of accidents. The reason for this recurring peak period closure was the high crash rates on the freeway at this location.
The peak period closure was successful at improving safety in the area. The Wisconsin Department of Transportation WisDOT conducted a detailed accident analysis at this location because it has an extremely high crash rate in the range of ten times higher than all other locations in southeastern Wisconsin.
The analysis indicated that approximately 80 to 90 percent of the crashes were occurring during the afternoon peak period. The ramp was equipped with a gate that automatically closed during the times of closure and opened immediately after.
It should also be noted that this gate required extensive maintenance. The gate was often broken by traffic determined to use the ramp anyway and would again be broken within weeks of repair.
This ramp will be closed permanently with the reconstruction of the Marquette Interchange. There are various ways to provide a ramp closure, and the design or configuration depends on the type of closure and other factors. Figure shows an example of how the Hawaii DOT used traffic cones to temporarily close the Lunalilo Street on-ramp and the Vineyard Boulevard off-ramp along the westbound H-1 freeway.
More detailed information about this closure can be found in Chapter When construction occurs on or adjacent to a ramp, the construction may include single lane closures. There are a variety of design considerations in selecting the type of closure device, based on its application.
Manuals provide policy and guidance to staff, local agencies, contractors, and consultants to help us deliver an efficient and effective multimodal system. Project Delivery Memos are design and construction documents used to implement an immediate change in any stage of project, from design through advertisement and construction.
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