Strategies for Work Zone Transportation Management Plans (2020) / Chapter Skim
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7 Work Zone Safety Management Strategies This section includes work zone strategies and supportive technologies that transportation agencies use to address traffic safety concerns in work zones. The following strategies are covered in this section: • Work zone posted speed limit reduction • Portable variable speed limit system • Temporary rumble strips • Sequential flashing warning lights • Automated flagger assistance devices • Work zone intrusion alarm • Moveable traffic barrier systems 2.1 Work Zone Posted Speed Limit Reduction 2.1.1 Description The 2009 MUTCD, Section 1A.13, defines posted speed limit (PSL)
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8 Strategies for Work Zone Transportation Management Plans 2.1.2 When to Use To assist in determining the need for work zone speed limit reduction, flowcharts were developed by the FHWA (Figure 2.1) and the New York State Department of Transportation (NYSDOT)
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Figure 2.1. Flowchart for setting work zone speed limits (Credit: FHWA)
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Figure 2.2. Work zone regulatory speed limit reduction flowchart (Credit: NYSDOT)
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Work Zone Safety Management Strategies 11 • Expressways and other multilane highways with 55 or 50 mph speed limit. Reduce to 45 mph only in situations that have a combination of extreme lane shifts, narrowed lanes, bidirectional traffic, or milled surfaces.
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12 Strategies for Work Zone Transportation Management Plans 70 mph. The scenarios involved (1)
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Work Zone Safety Management Strategies 13 The MUTCD guidance corresponds with conclusions of field research such as Migletz et al.
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14 Strategies for Work Zone Transportation Management Plans engineering judgment indicates the need for advance notice to comply with the PSL ahead. If used, REDUCED SPEED LIMIT AHEAD signs must be followed by a SPEED LIMIT sign (R2-1)
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Work Zone Safety Management Strategies 15 record or collect speeds from passing motorists. The digital signs are only programmed to post the speed limit in a construction work zone and flash lights intermittently.
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16 Strategies for Work Zone Transportation Management Plans MnDOT. Speed Limits in Work Zones Guidelines, Minnesota Department of Transportation, October 2014.
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Work Zone Safety Management Strategies 17 2.2.2 When to Use PVSLS may be considered for deployment when the following conditions are anticipated: • Work zone will cause 10 minutes or more of additional travel time. • Work zone queue is estimated to slow traffic at least 10 mph below the PSL.
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18 Strategies for Work Zone Transportation Management Plans The following project types are unsuitable for PVSLS deployment because of the complexities involved in implementation, placement, and monitoring of conditions: • Projects involving moving operations (striping, grinding rumble strips, etc.)
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Work Zone Safety Management Strategies 19 Several other field studies on both regulatory and advisory PVSLSs provided inconclusive results (Saito and Wilson 2011; Fudala and Fontaine 2010; Riffkin et al. 2008; Michigan Department of Transportation 2003)
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20 Strategies for Work Zone Transportation Management Plans • Semiautomated implementation. This process would use an algorithm that collects field data (speed, volume, and occupancy)
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Work Zone Safety Management Strategies 21 that summarized the PVSLS operational parameters and limits, user and system needs, stakeholder needs and responsibilities, operational scenarios, testing/validation, data collection, performance monitoring, and safeguards, as well as the system devices needed and where they are to be deployed within the work zone. At the time this guidebook was written, UDOT had completed 2 years of PVSLS system deployment testing in four construction work zones to evaluate the effectiveness of the system (refer to Section 2.2.4 for results)
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Figure 2.7. UDOT PVSLS standard drawing (Credit: UDOT)
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Work Zone Safety Management Strategies 23 2.2.10 Resources and References Edara, P., C
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24 Strategies for Work Zone Transportation Management Plans 2.3 Temporary Rumble Strips 2.3.1 Description The 2009 MUTCD, Section 6F.87, defines transverse rumble strips as "intermittent, narrow, transverse areas of rough-textured or slightly raised or depressed road surface that extend across the travel lanes to alert drivers to unusual vehicular traffic conditions. Through noise and vibration they attract the driver's attention to such features as unexpected changes in alignment and to conditions requiring a stop." "Temporary rumble strips" (TRSs)
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Work Zone Safety Management Strategies 25 visual obstructions, nighttime work zones, and more. The circumstances and the type of TRS used vary considerably, as discussed by the DOT examples to follow.
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26 Strategies for Work Zone Transportation Management Plans fatigued, or sleepy drivers. An increase in driver awareness can lead to positive behavior modification in speed reduction, braking, and increased compliance with warning signs and devices -- all of which are behaviors that can reduce crashes in work zones.
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Work Zone Safety Management Strategies 27 Washington State legislature, the Washington State Department of Transportation (WSDOT) developed a MOTORCYCLES USE EXTREME CAUTION warning sign (W21-1701 in the WSDOT Sign Fabrication Manual)
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28 Strategies for Work Zone Transportation Management Plans 2.3.9 Cost A single portable plastic rumble strip costs about $1,500. A minimum of three strips is required to form an array (or set)
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Work Zone Safety Management Strategies 29 The Missouri DOT's (MoDOT) practice is to use SEQ on rural work zones with a high percentage of truck traffic.
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30 Strategies for Work Zone Transportation Management Plans 2.4.6 Implementation Considerations SEQs must flash sequentially beginning with the first light and continuing until the final light and in sequence when placed on the drums that form the merging taper. SEQs should be visible on a clear night from a distance of 3,000 ft.
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Work Zone Safety Management Strategies 31 Figure 2.12. MoDOT SEQ guidance (Credit: MoDOT)
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32 Strategies for Work Zone Transportation Management Plans 2.4.10 Resources and References Finley, M
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Work Zone Safety Management Strategies 33 2.5.3 Benefits The primary benefit of AFADs is to enhance the safety of flaggers while also maintaining positive control of traffic approaching the work zone. 2.5.4 Expected Effectiveness State evaluations have generally found drivers understand the red/yellow lens version better than the stop/slow version.
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34 Strategies for Work Zone Transportation Management Plans the 2009 MUTCD and crashworthiness standards, advanced warning signs must alert traffic in both directions of an impending stop. When not in use, AFADs need to be removed from the clear zone and advanced warning signs covered.
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Work Zone Safety Management Strategies 35 Cottrell B
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36 Strategies for Work Zone Transportation Management Plans taper are high, and sight distance is limited. A study conducted for Alabama DOT (Marks et al.
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Work Zone Safety Management Strategies 37 – The study conducted by Gambatese, Lee, and Nnaji (2017) found similar results to the Novosel study.
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38 Strategies for Work Zone Transportation Management Plans 2.6.6 Implementation Considerations The following guidelines should be considered for using WZIAs (Gambatese, Lee, and Nnaji 2017) : • Sound level.
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Work Zone Safety Management Strategies 39 maximum distance of 225 feet between the first alarm unit and the nearest trip hose. Additional trip hoses upstream of the first trip hose are recommended to increase the coverage area in the work zone.
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40 Strategies for Work Zone Transportation Management Plans to be used in the presence of heavy vehicles and speeds exceeding 35 mph. For other speeds, the very high sensitivity lamp should be used.
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Work Zone Safety Management Strategies 41 2.6.8.2 Advanced Warning and Risk Evasion In addition to the intrusion alarm systems listed previously, Oldcastle Materials recently introduced Advanced Warning and Risk Evasion (AWARE) alert technology.
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42 Strategies for Work Zone Transportation Management Plans 2.6.10 Resources and References Brown, H., C
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Work Zone Safety Management Strategies 43 Some other work activities warranting moveable barriers are • Pothole filling, • Overnight slab replacement, • Light bulb changes on highways, • Joint seal replacements, • Work required on medians, • Bridge rehabilitation, • Culvert replacements, • Guardrail replacements, and • Pavement distress surveys. 2.7.3 Benefits Moveable barriers allow field crews to safely and quickly create a work space that is physically separated from moving traffic and then quickly remove the device from the roadway when the work activity is completed, restoring normal traffic flow.
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44 Strategies for Work Zone Transportation Management Plans 2.7.7.2 MBT-1 Similar to the Balsi Beam, the proprietary MBT-1 barrier consists of a 5-ft-tall smooth steel wall that protects the work zone from the side, combined with an attenuator at the rear (Figure 2.21)
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Work Zone Safety Management Strategies 45 Lohse, C., D
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