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32 Case Example #1: Washington State DOT WSDOT has included a âVery Short Duration Work Zoneâ section in its Work Zone Traffic Control Guidelines for Maintenance Operations (WSDOT 2018). VSDWZ activities listed in the document include â¢ Removing lost cargo or debris. â¢ Installing or removing a work zone device. â¢ Taking a survey shot. â¢ Providing motorist assistance. â¢ Performing quick maintenance or repairs intended as a partial or temporary response to an issue. When short duration plans are to be used, the proper work zone condition (A, B, or C) needs to be determined. This helps to establish a practical application level of traffic control devices to use. Work zone conditions are defined as follows: â¢ Condition AâRepresents the lowest level of exposure: â Low traffic speeds and volume. â Minimum levels of traffic control devices to place and remove. â¢ Condition BâRepresents a moderate level of exposure: â Low or high traffic speed with low to moderate volumes. â Moderated levels of traffic control devices for warning and protection, such as adding a spotter, placing cones, or adding portable change message signs (PCMSs) to Condition A devices. â¢ Condition CâRepresents the highest level of exposure: â High traffic speeds and volume. â All applicable traffic control and safety devices need to be considered (e.g., PCMSs, TMAs, and signs). Highway volumes can be identified by the following observations: â¢ Low volumeâ â Vehicles approach randomly. â Significant gaps in traffic flow. â Few vehicles visible at any given time. â Random platoons of vehicles. â Free-flow traffic at the posted speed limit. â Safe walking-pace conditions to cross a two-lane highway or intersection. â Rough estimate of traffic volume at less than five vehicles per lane per minute. C H A P T E R 4 Case Examples
Case Examples 33 â¢ Moderate volumeâ â Random gaps in traffic. â Vehicles generally present all the time. â Traffic constant but still flows freely. â Safe walking-pace conditions to cross a two-lane highway or intersection, but may require waiting for a gap in traffic. â Rough estimate of traffic volume at 12 vehicles per lane per minute. â¢ High volumeâ â Minimal gaps in traffic. â Constantly present vehicles. â Restricted or unstable traffic flow. â Reduced traffic speeds as volume starts to approach road capacity. â Safe walking conditions to cross a two-lane highway or intersection may not exist. â A rough estimate of 20 vehicles per lane per minute. The guidelines advise that live traffic areas (lanes and intersections) on high-speed and high-volume roadways may not be good candidates for short duration work zones. Shoulder or adjacent lane work may be acceptable based on a site assessment and as follows: No unprotected work in interior lanes of multilane roads and no island work areas are allowed. Lanes of multi- lane roads may only be accessed from the adjacent shoulder (see TCP 26 and TCP 27). Intersections may be accessed following the same manner, and consideration needs to be given to the work areaâs effect on the intersection signal operations. Flash mode or control measures per TCP 14 or TCP 15 may be required. A determination of a safe work location must be made. A basic determination can be made by observing traffic conditions (speed, volume, location, visibility, etc.) and assessing the following conditions: â¢ Is the work location out of the traffic path? â¢ Is there sufficient time for a worker to safely walk (not run) to and return from the work location? â¢ Are there other hazards at the location that could affect worker safety? â¢ Is there an effective contingency or escape plan? â¢ Is there adequate sight distance from the work location to approaching traffic? Consideration could be given to a rolling slowdown operation for those VSD work operations in which traffic control measures would take more time to install than the actual work. Typically, rolling slowdowns are desirable for difficult-access work zones, such as center lanes, or when closing all lanes at once on multilane highways. Linking several short duration work operations under a stationary lane or shoulder closure with a full complement of signs and devices could also be considered. Advantages include reduc- ing exposure of workers to traffic, increasing efficiency in completing tasks concurrently, and reducing the impacts to traffic in the same area. In many cases, it is necessary and allowable for workers to walk on a roadway shoulder, cross traffic lanes, or momentarily step into a lane to access work locations or to perform work. These actions can only be accomplished if traffic conditions allow them to be done safely. WSDOT has five TAs for VSDWZs, which are shown in Figure 19 through Figure 23. Each TA denotes the work zone conditions under which it is allowed to be used. Figure 19 shows an application for work outside the traveled way for both two-lane and multilane situations. This plan depicts typical work zone scenarios that may occur at various locations outside of live lanes and other live traffic areas such as merge areas and ramp lanes. These non-traffic areas outside
34 Very Short Duration Work Zone Safety for Maintenance and Other Activities the traveled way are common locations to park a work vehicle to gain access to a location for VSD work such as inspection, survey shot, and field recon. Figure 20 shows a low-speed (40 mph or less) multilane application. This plan depicts typical work zone scenarios that may occur at various lane and shoulder locations along a low-speed multilane highway for work operations such as minor pothole repair or other VSD work that does not actually close or block the lane. As vehicles approach, it is incumbent on the worker to move back to the adjacent shoulder. More than two or three attempts to complete the work may indicate the need for a short duration or stationary work zone setup. Figure 21 shows a multilane freeway and highway application where the speeds are 45 mph or higher. This plan depicts two typical VSDWZ scenarios that may occur in live high-speed traffic lanes. Work operations may include minor pothole or debris removal that may be accomplished without presenting an unacceptable hazard to the worker or traffic. Figure 19. WSDOT TCP 25 typical very short duration work operation (outside traveled way; WSDOT 2018).
Case Examples 35 Approaching traffic is allowed to pass through the work location, and a spotter is used to alert the worker to move back to the shoulder as traffic approaches. Work that cannot allow traffic to pass through the work location could be performed as a short duration or stationary lane closure. Figure 22 shows a two-lane highway application. This plan depicts two typical VSDWZ scenarios that may occur in live traffic lanes on either a low- or high-speed roadway. Work operations may include minor pothole repair or debris removal that may be accomplished without presenting an unacceptable hazard to the worker or traffic. Approaching traffic is allowed to pass through the work location, and a spotter is used to alert the worker to move back to the shoulder as traffic approaches. Work that cannot allow traffic to pass through the work location could be performed as a short duration or stationary lane closure. Figure 20. WSDOT TCP 26 typical very short duration work operation (multilane application, low speed, 40 mph or lower; WSDOT 2018).
36 Very Short Duration Work Zone Safety for Maintenance and Other Activities Finally, Figure 23 shows an intersection application. This plan depicts typical work zone scenarios that may occur in intersections, such as verifying field data, taking a survey shot, inspecting for damage, and so forth. Case Example #2: Florida DOT FDOT uses statewide construction standards for performing maintenance work. One of the TAs with the lane closure exceptions, âStandard Index 613 Multilane, Work Within Travel Way, Median or Outside Lane,â is shown in Figure 24. Duration notes have recently been added to this standard index to allow for fewer TTC devices in stationary lane closures if certain conditions are met. The duration notes state the following: 1. Temporary white edgeline may be omitted for work operations less than 3 consecutive calendar days. 2. For work operations up to approximately 15 minutes, signs, channelizing devices, arrow board, and buffer space may be omitted if all of the following conditions are met: a. Speed limit is 45 mph or less. b. No sight obstructions to vehicles approaching the work area for a distance equal to the buffer space and the taper length combined. Figure 21. WSDOT TCP 27 typical very short duration in-lane work (multilane freeway and highway application, high speed, 45 mph or higher; WSDOT 2018).
Case Examples 37 c. Volume and complexity of the roadway has been considered. d. The closed lane is occupied by a class 5 or larger, medium duty truck(s) with a minimum gross weight vehicle rating (GWVR) of 16,001 lb with high-intensity, rotating, flashing, oscillating, or strobe lights mounted above the cab height and operating. 3. For work operations up to 60 minutes, arrow board and buffer space may be omitted if conditions a, b, and c in DURATION NOTE 2 are met, and vehicles in the work area have high-intensity, rotating, flashing, oscillating, or strobe lights operating. Similar duration notes exist on the FDOT âStandard Index 615 Multilane Work in Intersectionâ and âStandard Index 616 Multilane Work Near Intersection, Median or Outside Laneâ sheets (FDOT 2015). Case Example #3: Maine DOT Maine DOT has outlined a basic procedure for short duration work zones that last up to 30 minutes. Although the term âvery short durationâ is not used, the duration requirement for using this procedure is 30 minutes, which is much shorter than the hour allowed under the national MUTCD for short duration work. The procedure is shown below in its original form (see Exhibit 1). Figure 22. WSDOT TCP 28 typical very short duration lane closure (two-lane highway; WSDOT 2018).
38 Very Short Duration Work Zone Safety for Maintenance and Other Activities Figure 23. WSDOT TCP 29 typical very short duration work operation (intersection application; WSDOT 2018). Figure 24. FDOT Standard Index 613 TA (FDOT 2015).
Case Examples 39 I. Scope: This procedure has been established to set guidelines for temporary traffic control in work zones of short duration, as they apply to Maine DOT workers. The MUTCD (Section 6G-2) recognizes the need for safety in these operations. Maine DOT defines this work as approximately 30 minutes or less of exposure to employee(s) in one specific location. II. General Requirements: A. The MUTCD maintains that during short-duration work, it often takes longer to set up and remove the temporary traffic control zone than to perform the work. Workers face hazards in setting up and taking down the temporary traffic control zone. Also, since the work time is short, delays affecting road users are significantly increased when additional devices are installed and removed. Considering these factors, simplified control procedures may be warranted for short-duration work of approximately 30 minutes or less. A reduction in the number of devices may be offset by use of other more dominant devices such as rotating lights or strobe lights on work vehicles. Proper PPE must always be worn in accordance with existing policies. This procedure is intended to decrease the amount of time our workers are exposed to vehicular traffic and therefore improve overall safety, not to make the job easier or quicker at the expense of safety. B. Examples of Short-Duration Work could include but are not limited to: 1. Removal of a dead animal in the road that may involve simply shoveling up the animal to dispose of it properly or dragging it to the side of the road. 2. Removal of debris from the roadway. 3. Patching a pothole that requires immediate attention and is not part of a planned patching operation. 4. Cutting a small amount of vegetation that may be obstructing a sign or hanging over a guardrail. 5. Straightening a sign that does not require resetting. C. Minimum criteria to consider the use of the short duration method: 1. Whenever possible and available, vehicles should be parked completely in the shoulder and out of the travel way. 30 250 5 35 305 5 40 360 5 Â½ 45 425 5 Â½ 50 495 6 55 570 6 Â½ 60 645 6 Â½ 65 700 7 2. There must be adequate sight distance, as listed below, in both directions. Speed Limit (MPH) Safety Sight Distance (Feet) Approx. Stopping Time (Sec) 25 200 4 Â½ Exhibit 1. Short duration work zone procedure. (continued on next page)
40 Very Short Duration Work Zone Safety for Maintenance and Other Activities Case Example #4: Minnesota DOT The MnDOT field manual provides three layouts for mobile operations on two-lane, two-way roads. Layout 11 (shown in Figure 25) may be used for roads with traffic volume fewer than 1,500 average daily traffic (ADT), with good visibility, and during daytime conditions (or night- time if the posted speed limit is 40 mph or less), and if the operation moves more than distance D every 15 minutes. Calculated values for D and other dimensions shown in the layouts are given in Table 7. Layout 11 consists of a single work vehicle (with appropriate lighting) that can encroach into the lane where the work is being performed. The shadow vehicle and warning sign are not required. This layout could be used for pothole patching or debris removal. When the traffic volume is greater than 1,500 ADT and the work operation moves more than distance D every 15 minutes, Layout 12 (shown in Figure 26) can be used, provided that the work space is visible to motorists for a distance D upstream, the motorists can see beyond the work space, and traffic volumes allow passage. When these conditions are not met, Layout 13 (shown in Figure 27) can be used. This layout closely resembles the national MUTCD TA 10 (shown in Figure 28), except that the channelizing devices are omitted and replaced with a protection vehicle. The MnDOT field manual is unique in that it offers TTC strategies that fill the gap between mobile operations and a stationary lane closure, when certain conditions are met. 3. The job will take approximately 30 minutes or less. Should it become apparent that magnitude or scope of the work has changed such that it will significantly exceed the approximately 30-minute timeframe, then the work zone should be converted to a short-term stationary operation. If it is uncertain if the work will take approximately 30 minutes or less, use traffic control devices to set up a work zone as a short-term stationary operation. 4. If the work to be accomplished is within the traveled way and will require focused attention for a period of time greater than or equal to the time that it takes a vehicle to traverse the available sight distance, then a lookout (person other than the one doing the work) must keep an eye on traffic. The lookout cannot direct or âflagâ traffic, because flagging requires proper signing and paddles. 5. Traffic volume must be low enough to provide adequate gaps to perform the task. 6. This application requires good judgment since each temporary traffic control zone is different. Many variables, such as location of work, road type, geometrics, vertical and horizontal alignment, intersections, interchanges, traffic volumes, vehicle mix (buses, trucks, and cars), and speed of traffic affect the needs of each zone. The goal of every temporary traffic control zone is safety with minimum disruption to road users. 7. When used, the justification for using this procedure must be documented as an option on a JSA [job safety analysis] or Traffic Control Plan for that dayâs work. For example, if patrolling roads only one JSA is needed for the day, not for every instance where the short duration procedure is used. A JSA is not required in single or emergency cases where immediate action is required. III. Training All employees who perform operations that require traffic control will be trained on the contents of this procedure. Exhibit 1. (Continued).
Case Examples 41 Figure 25. MnDOT field manual Layout 11 lane closure (MnDOT 2018). Note: G represents the channelizing device spacing. Table 7. MnDOT TTC distance chart (MnDOT 2018).
42 Very Short Duration Work Zone Safety for Maintenance and Other Activities Figure 26. MnDOT field manual Layout 12 lane closure (MnDOT 2018).
Case Examples 43 Figure 27. MnDOT field manual Layout 13 lane closure (MnDOT 2018).
44 Very Short Duration Work Zone Safety for Maintenance and Other Activities Figure 28. MUTCD TA 10 lane closure (FHWA 2009).