Strategies for Work Zone Transportation Management Plans (2020)

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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) as “a speed limit deter- mined by law or regulation and displayed on speed limit signs.” Speed limit reduction is the process of lowering the PSL for a particular segment of a roadway resulting from changes in geometry, land use, traffic volumes, and crashes or crash potential along the highway. Work zones and school zones are two examples of where reduced speed limits are used; however, normal PSL is resumed beyond the end of the work zone. Two types of reduced speed limits operate in work zones: 1. Restricted speed limits are regulatory speed limits3 used only when the work zone and workers are in operation, typically from 9:30 a.m. to 3:30 p.m. and from 9:00 p.m. to 5:00 a.m. During periods of no activity or when the traffic controls are removed from the roadway, the speed limit signs are covered or removed. This involves installing (or uncovering) signs at the beginning of a work shift and removing (or covering) signs at the end of the shift. 2. 24/7 construction speed limits are regulatory speed limits established for long-term projects when motorists must reduce speeds to safely navigate the work zone. These speed limits are intended for a 24-hour continuous posting so, unlike the restricted speed limits, they are not taken down at the end of the work shift. C H A P T E R 2 3 The 2009 MUTCD (Section 1A.13) defines a regulatory sign as “a sign that gives notice to road users of traffic laws or regulations.”

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) (Figure 2.2). The exact criteria used in setting work zone speed limits vary jurisdictionally. As examples of state policies and procedures, guidance on setting work zone speed limits from the Virginia DOT (VDOT), the Wisconsin DOT (WisDOT), and the Ministry of Transportation of Ontario is discussed. 2.1.2.1 Virginia VDOT provides the following warrants for reduced speed limits on short-term (<72 hours) work zones on an Interstate or other limited-access, multilane, divided highway with a PSL of 55 mph or greater.4 • A lane closure resulting in congestion expected to reduce vehicle operating speeds by at least 10 mph for most of the time the work zone is in place; or • Pavement surface conditions such as uneven, ridged, or broken pavement or potholes that destabilize vehicles for most of the work zone; or • Workers within 2 ft of a travel lane for most of the time the work zone is in place; or • Lane-width reductions resulting in travel lanes less than 11 ft wide for most of the work zone; or • Work activity that reduces the sight distance available to motorists below that required at the original PSL for the majority of the time the work zone is in place. VDOT’s recommended guidelines for increased fines are as follows: • Projects on limited-access highways with work duration of 60 days or more, • Projects on non–limited access highways with a PSL of 35 mph or greater that will have a work duration of 120 days or more, and • Projects (both limited and non–limited access highways) where safety will be improved based on the engineering judgment of the regional traffic engineer. 2.1.2.2 Wisconsin WisDOT uses the following criteria, along with engineering judgment, to develop an appro- priate work zone speed limit. The most restrictive work zone impact is used as the determining condition.5 • Interstates and expressways with 70 or 65 mph speed limit: – If tubular markers separate bidirectional traffic, then reduce to 55 mph. – If workers are present within 12 ft of live traffic without positive protection,6 then reduce to 55 mph. – If the work zone is less than or equal to 0.5 mi long, with lane shifts or narrowed travel lanes and positive protection, then post warning signs with an advisory speed plaque. – If the work zone is less than or equal to 0.5 mi long, with no lane shifts or narrowed travel lanes and positive protection, then do not lower the speed limit. – If work is taking place outside the clear zone, then do not lower the speed limit. – Reduce all other work zones to 60 mph (70 to 60 mph or 65 to 60 mph). 4 Traffic Engineering Division Memorandum Number TE-340.1: Speed Limit and Fine Signs in Work Zones, 2012. 5 Traffic Engineering, Operations and Safety Manual, Section 13-5-6: Temporary Traffic Control Zones, February 2018. 6 FHWA defines positive protection as a temporary precast concrete barrier that contains or redirects vehicles and separates workers from the active travel lanes.

Figure 2.1. Flowchart for setting work zone speed limits (Credit: FHWA).

Figure 2.2. Work zone regulatory speed limit reduction flowchart (Credit: NYSDOT).

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. Restore speed limit to normal posted speed when reduction criteria are not present. • Multilane highways with 45 mph speed limit. Reduce speed limit to 35 mph only in situa- tions that have a combination of extreme lane shifts, narrowed lanes, bidirectional traffic, or milled surfaces. • Two-lane rural highways with 55 mph speed limit. Reduce to 45 mph only in situations that have a combination of extreme lane shifts, narrowed lanes, or milled surfaces. The flagging operation in itself would not typically warrant a reduced speed limit because motorists are controlled by the flagging devices. • Two-lane rural roadways with speed limit of 45 mph of less. Do not reduce speed limit in typical cases, but consider a speed reduction of up to 10 mph in increments of 5 mph in situa- tions with a combination of extreme lane shifts, narrowed lanes, or milled or gravel surfaces. • Two-lane urban roadways with speed limit of 40 mph or less. Do not change the speed limit, but consider reducing it to 35 mph in situations that have a combination of extreme lane shifts, narrowed lanes, or milled or gravel surfaces. 2.1.2.3 Ontario The January 2014 edition of the Ontario Traffic Manual, Book 7 (MTO 2014), provides guidelines for determining when to reduce speed limits in work zones (Table 2.1). 2.1.3 Benefits Reducing speed limits in work zones provides the following benefits: • Encourages speed limit compliance, thereby reducing crash potential, and • Improves worker safety. 2.1.4 Expected Effectiveness Hou, Edara, and Sun (2011) evaluated three speed limit scenarios on three short-term Interstate work zones in Missouri; the speed-reduction scenarios had standard speed limits of Method Examples Restricted speed limits. Used only when workers present. Workers on a freeway within 10 ft of a traveled lane open to traffic where no barrier is used 24/7 construction speed limits. Used for continuous public and worker safety on long-duration construction with continuous hazards, or where uninterrupted flow cannot be designed at or above the normal regulatory posted speed (substandard geometrics). Used 24 hours a day. Lane width less than 12 ft (3.5 m) on freeways or less than 10 ft (3.0 m) on nonfreeways Shoulder width or offset to barriers less than 1½ ft (0.5 m) on one or both sides Sudden lane narrowing Substandard sightlines or stopping sight distance Multiple lane shifts, detours, or transitions designed at less than the normal PSL, or those with no illumination Substandard horizontal or vertical alignment Gravel surfaces (length greater than ¼ mi, or 500 m) Multiple lane shifts with confusing pavement markings Partial lane shifts onto a surface different from the main roadway NOTE: PSL = posted speed limit. SOURCE: MTO (2014). Table 2.1. Appropriate use of speed limit reductions in work zones from the Ontario Traffic Manual, Book 7.

12 Strategies for Work Zone Transportation Management Plans 70 mph. The scenarios involved (1) no reduction in the PSL, (2) a 10-mph reduction in the PSL, and (3) a 20-mph reduction in the PSL, respectively. The 85th percentile speeds and speed variance for the three scenarios were 81 mph and 10 mph, 62 mph and 8 mph, and 48 mph and 6 mph, respectively. The percentage of drivers who exceeded the PSL by more than 10 mph in each scenario was 15.4 percent, 4.8 percent, and 0.9 percent, respectively. The 20-mph speed limit reduction scenario proved most effective in lowering prevailing speeds and speed variance. The Colorado DOT (CDOT) evaluated seven speed limit reduction scenarios in increments of 5 mph (i.e., 75, 70, 65, 60, 55, 50, and 45 mph). With the normal 75-mph PSL from the high- way reduced to 65 mph, 85 percent of drivers complied with the lower limit (within 2 mph). This can be considered a successful speed limit that drivers respect—fewer than about 1 in 25 exceeded the limit by more than 5 mph. When the speed limit was reduced 15 mph or more, however, the number of drivers exceeding the PSL increased sharply from slightly less than 1 in 17 at a 15-mph reduction to nearly 1 in 3 at a 30-mph reduction. 2.1.5 Crash Modification Factor The CMF for a work zone speed limit reduction appears to show a minor effect on crash risk, as shown in Table 2.2. Chapter 13 of this document provides more information on developing WZCMFs. 2.1.6 Implementation Considerations Part 6 of the MUTCD discusses speed limit reduction for temporary traffic control (TTC) zones. Section 6C.01 of the 2009 MUTCD states, Reduced speed limits should be used only in the specific portion of the TTC zone where conditions or restrictive features are present. A TTC plan should be designed so that vehicles can travel through the TTC zone with a speed limit reduction of no more than 10 mph. Reduced speed zoning (lowering the regulatory speed limit) should be avoided as much as practical because drivers will reduce their speeds only if they clearly perceive a need to do so. Research has demonstrated that large reductions in the speed limit increase speed variance and the potential for crashes. Smaller reductions in the speed limit of up to 10 mph cause smaller changes in speed variance and lessen the potential for increased crashes. A reduction in the regulatory speed limit of only up to 10 mph from the normal speed limit has been shown to be more effective. Crash Type Crash Severity Facility Type Volume Range CMF Standard Error Lower posted speed by 5 mph All All Urban and rural freeways Not specified 1.17 Not specified Lower posted speed by 10 mph All All Urban and rural freeways Not specified 0.96 Not specified Lower posted speed by 15 to 20 mph All All Urban and rural freeways Not specified 0.94 Not specified NOTE: The CMFs were derived from past studies on non–work zone roads, so their potential applicability to a work zone situation is unclear. Use these values with caution for work zones, because reduced work zone speed limits are often connected to other changes in the roadway cross section. CMF = crash modification factor. Table 2.2. CMFs for work zone speed limit reductions.

Work Zone Safety Management Strategies 13 The MUTCD guidance corresponds with conclusions of field research such as Migletz et al. (1999) and NCHRP Research Results Digest 192 (Transportation Research Board 1996). In general, the original PSL and road type are important factors for DOTs to consider, as are the presence of workers, their proximity to traffic, project length, project duration, area type (i.e., urban versus rural), occurrence of night work, traffic mix (e.g., commuter, recreational, truck percentages), and geometric changes. Another important factor frequently considered is the type of separation between workers and traffic (e.g., drums versus concrete barrier). Some state DOTs regulate work zone speed limit reductions based on worker proximity to traveled way and the presence of positive protection. For example, Michigan DOT (MDOT) does not allow a speed limit reduction when work activities, workers, materials, and equipment are more than 15 ft from the edge of the traveled way. Similarly, CDOT does not recommend speed limit reduction when the distance to the work is more than 10 ft from the edge of the traveled way, or when the work area is protected by concrete barrier and lane widths are not reduced. 2.1.7 Design Features and Requirements Any speed limit reduction must be accompanied by the appropriate signs. Figure 2.3 shows the MUTCD-recommended regulatory signs and plaques for use with reduced work zone speed limits.7 2.1.7.1 Upstream of the Work Zone • The sign must consist of a black and white SPEED LIMIT sign (R2-1) with a black and orange WORK ZONE plaque (G20-5aP) installed above the SPEED LIMIT sign. • Use a REDUCED SPEED LIMIT AHEAD (W3-5 or W3-5a) sign to inform road users of a reduced speed zone where the speed limit is being reduced by more than 10 mph, or where Figure 2.3. Reduced speed limit regulatory signs and plaques (Credit: 2009 MUTCD). 7 The difference between a plaque and a sign is that a plaque cannot be used alone.

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) installed at the beginning of the zone where the speed limit applies. • If increased fines are imposed for traffic violations within the work zone, then – Install a BEGIN HIGHER FINES ZONE (R2-10) sign at the upstream end of a work zone where increased fines are imposed for traffic violations. Alternate legends such as BEGIN DOUBLE FINES ZONE may also be used for the R2-10 sign. – Mount a FINES HIGHER (R2-6P), FINES DOUBLE (R2-6aP), or $X FINE (R2-6bP) plaque below the speed limit. 2.1.7.2 Downstream of the Work Zone • Install END WORK ZONE SPEED LIMIT (R2-12) sign. • If increased fines are used, then install an END HIGHER FINES ZONE (R2-11) sign. Alternate legends such as END DOUBLE FINES ZONE may also be used for the R2-11 sign. Individual signs and plaques for work zone speed limits and higher fines may be combined into a single sign or displayed as an assembly of signs and plaques. 2.1.7.3 Ohio In September 2012, legislative changes to Ohio Revised Code 4511.98 (http://codes.ohio.gov/ orc/4511) enabled the Ohio DOT (ODOT) to establish electronic speed limits in construction zones. Electronic work zone variable speed zones are permitted on multilane highways with speed limits of 55 mph or greater when workers are present for 3 or more consecutive hours, within the closed lanes or within 10 ft of the edge of the traveled way, and without positive protection. The intent of the electronic speed limit signs is to lower the speed limits “based on the type of work being conducted, the time of day when the work will be done, and any other criteria deemed appropriate by the Director of Transportation.” The legislation allows the speed limit to be reduced 10 mph lower than the original non–work zone PSL. The reduction in the PSL is conveyed to motorists through the portable, trailer-mounted digital sign displaying the speed limit for the work area. There are also flashing lights and text, WORK ZONE or WORKERS PRESENT, to notify motorists they are driving through a construction zone (Figure 2.4). The digital signs do not use radar or any other technology to Figure 2.4. ODOT variable speed limit signs (Credit: ODOT).

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. 2.1.8 State of the Practice 2.1.8.1 Policy and Warrants for Work Zone Speed Reduction NCHRP Synthesis 482: Work Zone Speed Management (Shaw et al. 2015) reports that 64 percent of state DOTs have a formal policy or guideline for determining when to reduce speed limits in work zones. In most cases, these documents also establish an agency-specific administrative process for approving speed reductions. Section 2.1.2 provides examples of states’ policies and procedures on setting work zone speed limits. 2.1.8.2 State Laws to Enforce Work Zone Speed Limits According to the Governors Highway Safety Association,8 all U.S. states have laws that increase the penalties for speeding or committing other traffic violations while in a construction work zone. The enhanced penalty is often a doubling of the fine applicable had the same traffic violation been committed outside a construction zone. It may also be a fixed-dollar amount or a range. In many states, the enhanced penalty is applicable only when workers are present or if suitable signs are posted that notify drivers of increased fines. • 22 states require workers and signs to be present for the increased penalties to take effect (Alabama, Arizona, Arkansas, California, Connecticut, Florida, Kentucky, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, North Dakota, Oklahoma, Pennsylvania, South Dakota, Tennessee, Texas, Utah, and Virginia). • 19 states and the District of Columbia require only signs to be present for the increased penalties to take effect (District of Columbia, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Maine, Maryland, Massachusetts, Michigan, New Jersey, New Mexico, New York, North Carolina, Ohio, Rhode Island, South Carolina, Vermont, and West Virginia). 2.1.9 Cost The costs for each static sign vary from $250 to $500, depending on the size. If a DOT is using electronic signs, such as speed display trailers, then costs may range between $8,000 and $10,000 per unit. Data-collection functionality adds an additional $5,000 per unit. 2.1.10 Resources and References Bham, G., and M. A. Mohammadi. Evaluation of Work Zone Speed Limits: An Objective and Subjective Analysis of Work Zones in Missouri. MATC REPORT # 25-1121-0001-119. February 2011. Brewer, M. A., G. Pesti, and W. H. Schneider, IV. Improving Compliance with Work Zone Speed Limits: Effectiveness of Selected Devices. Transportation Research Record: Journal of the Transportation Research Board, No. 1948, 2006, pp. 67–76. Guidelines to Establish Speed Limits in Work Zones, Michigan Department of Transportation, Bureau of Highway Instructional Memorandum 2005-16, December 2005. Hou, Y., P. Edara, and C. Sun. Speed Limit Effectiveness in Short-Term Rural Interstate Work Zones. Presented at 90th Annual Meeting of the Transportation Research Board, Washington, D.C., 2011. Manual on Uniform Traffic Control Devices. FHWA, U.S. DOT, 2009. http://mutcd.fhwa.dot.gov/. [MUTCD] Migletz, J., J. L. Graham, I. B. Anderson, D. W. Harwood, and K. M. Bauer. Work Zone Speed Limit Procedure. Transportation Research Record: Journal of the Transportation Research Board, No. 1657, 1999, pp. 24–30. Ministry of Transportation of Ontario (MTO), ed. Ontario Traffic Manual, Book 7, Temporary Conditions, Queen’s Printer for Ontario, Ottawa, ON, Canada, 2014. 8 Please see the GHSA Work Zones web page at https://www.ghsa.org/state-laws/issues/work%20zones (accessed May 12, 2020).

16 Strategies for Work Zone Transportation Management Plans MnDOT. Speed Limits in Work Zones Guidelines, Minnesota Department of Transportation, October 2014. NYSDOT. Engineering Instruction (EI) 08-030. Work Zone Speed Limit Reductions. New York State Department of Transportation, Albany, New York, September 9, 2008. ODOT. Signs as to Increased Penalties in Construction Zones. Ohio Revised Code (ORC), Section 4511.98, Effective date September 10, 2012. http://codes.ohio.gov/orc/4511.98. Accessed March 10, 2019. Outcalt, W. Work Zone Speed Control, Colorado Department of Transportation—Research, CDOT-2009-3, January 2009. Shaw, J. W., M. V. Chitturi, W. Bremer, and D. A. Noyce. NCHRP Synthesis 482: Work Zone Speed Management. Transportation Research Board, Washington, D.C., 2015. Transportation Research Board. NCHRP Research Results Digest 192: Procedure for Determining Work Zone Limits, September 1996. WSDOT. Speed Limit Reductions in Work Zones, Washington State Department of Transportation, Secretary’s Executive Order Number: E 1060.02, May 11, 2018. 2.2 Portable Variable Speed Limit System 2.2.1 Description A variable speed limit (VSL) system is a type of smart work zone (SWZ) system that uses traffic detection, weather information, and road surface–condition technology to determine appropriate speeds at which drivers should be traveling, given current roadway and traffic conditions. Sensors along the roadway collect conditions such as traffic volume, operating speeds, lane occupancy, and weather information. These data are typically transmitted to a transportation management center (TMC) and analyzed automatically with an algorithm or reviewed by agency personnel who decide the speed limit. Depending on the objectives set for the system, speed limits can be regulatory or advisory. These regulatory or advisory speeds are usually displayed on overhead electronic message boards, portable electronic speed trailers, or portable changeable message signs (PCMSs). Note that regulatory VSLs are enforceable, whereas advisory VSLs are not. Two common purposes for deploying VSLs are for weather-related conditions and for inci- dent management. Recently, there has been a renewed interest in expanding VSL functionality to work zones. This section discusses the use of VSLs in work zones, here referred to as “portable variable speed limit systems” (PVSLS). Figure 2.5 shows an example of regulatory PVSLS and Figure 2.6 shows an advisory PVSLS. Figure 2.5. Regulatory PVSLS trailer at a Utah work zone (Credit: Street Smart Rental).

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. • Traffic speeds through the project vary widely because of oversaturated conditions during the peak period, and the timing and extent of congested travel will vary significantly day to day. • Frequent planned lane closures are expected, which will create queues that cause high speed differentials between queued and approaching traffic. • Lower speed limits would be temporarily beneficial for the work activities that will frequently occur. The types of construction projects and work zones considered as good candidates for PVSLS deployment have the following characteristics: • Work duration of at least 30 days. A PVSLS is not recommended in a short-term work zone because of higher setup costs and longer testing and calibration times. • Roadways with higher speeds (45 mph or greater). • Four-lane divided or undivided roads (two lanes in each direction), maintaining at least a single through lane in each direction during construction. • Work zone projects where providing positive protection is not feasible (roadway resurfacing, roadway slab replacement, bridge deck replacement, etc.). • Roadways with sufficient traffic volume to measure (directional average daily traffic volumes between 7,500 and 25,000), but not in an area known to be frequently congested. • Roadways that are flat and straight (simple geometries with minimal curves and elevation changes). Figure 2.6. Advisory PVSLS trailer at a Missouri work zone (Credit: University of Missouri).

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.). • Projects with just shoulder work (i.e., too small a traffic impact to worry about). • Projects that use flagger control, pilot vehicles, and temporary signals. • Projects where lane closures will require positive protection. • Work zones too close (minimum 1 mi) to a traffic signal or other access control to eliminate external influences on the system. 2.2.3 Benefits The goal of PVSLs is to gradually reduce speeds of vehicles approaching the lane closure in an attempt to • Delay (and possibly prevent) congestion from forming at the lane closure. • Reduce the speed differential between congested and uncongested traffic flow at the back of the queue, and thereby – Reduce the potential for rear-end crashes. – Reduce the crash potential associated with lane merges at lane tapers. – Improve motorist and worker safety. 2.2.4 Expected Effectiveness Reported results of regulatory PVSLS studies include the following: • With the assistance of an FHWA Accelerated Innovation Deployment demonstration grant, the Utah DOT (UDOT) initiated a PVSLS program in 2014 and evaluated the effectiveness of a PVSLS at four work zones in 2016 and 2017 (UDOT 2018). When the PVSLS was activated, compared with baseline, speeding was reduced by – 15.1 percent for vehicles exceeding PSL by more than 15 mph (13.3 percent to 28.4 percent), – 25 percent for vehicles exceeding PSL between 10 and 15 mph, and – 83.4 percent for vehicles exceeding PSL by less than 10 mph. • The Texas DOT (TxDOT) evaluated the effectiveness of PVSLS in 2014 and reported speed reductions ranging between 2.5 mph and 4.2 mph when the PVSLS was active. The study also showed an increase in vehicles per hour per lane (vphpl) between 188 and 350. • The Maryland State Highway Administration (MDSHA) found an 8 percent increase in throughput, a 34 percent reduction in travel time during the congested half hour, and a 15 percent increase in average speed (Park and Chang 2010). Reported results of advisory PVSLS studies include the following: • Edara, Sun, and Hou (2013) evaluated variable advisory speed limits at four work zones in Missouri and reported the following results: – 2.2 mph reduction in mean speeds at an urban uncongested work zone, – 40 percent to 58 percent decrease in average queue length, – 6 percent to 13 percent reduction in work zone throughput and 20 percent to 29 percent decrease in number of stops per vehicle for an urban congested work zone, and – 2 mph reduction in mean speeds and 85th percentile speeds at rural work zones. • Kwon et al. (2007) reported a 25 percent to 35 percent decrease in speed variance, a 7 percent increase in throughput, and an increase in speed limit compliance during the morning peak period.

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 Depart- ment of Transportation 2003). 2.2.5 Crash Modification Factor Table 2.3 shows the CMF for a PVSLS. Chapter 13 of this document provides more informa- tion on developing WZCMFs. 2.2.6 Implementation Considerations Most, if not all, states have a speed-zoning statute that delegates to the DOT the power to establish or change speed limits. The states that have implemented PVSLS have done so mainly under the broad authority provided in this speed-zoning provision of state law or through a special provision (e.g., South Dakota and Texas). South Dakota House Bill 1008 (2018) states, The secretary of transportation may establish limited speed zones through highway work areas on the state trunk highways and on any segment of the interstate highway system based on monitored traffic, weather, or road surface conditions if the secretary of public safety and the secretary of transportation, after consultation with the director of the highway patrol, agree the limited speed zones are necessary for the protection of life and property. Differing speed limits may be established for different times of day, different types of vehicles, varying weather conditions, and any other factor that has a bearing on a safe speed. In December 2013, the Texas Transportation Commission established Rule §25.27 of the Texas Administrative Code, authorizing and requiring TxDOT to implement a VSL pilot program to “study the effectiveness of temporarily lowering prima facie speed limits to address inclement weather, congestion, road construction, or any other condition that affects the safe and orderly movement of traffic on a roadway.” The Judicial Enforcement of Variable Speed Limits report (Hines and McDaniel 2002) addresses legal considerations for implementing and enforcing VSLs; state DOTs should refer to this guidebook for more detailed information on this topic. DOTs can use also a commercial off-the-shelf (COTS) system to deploy PVSLS. The PVSLS could be a line item under TTC in a specification, and a COTS system could be competitively bid, thus relieving the DOT from procurement, operations, and maintenance burdens. Alternatively, the DOT could develop, procure, own, and operate the system. There are, however, many factors to consider if the DOT procures the devices for the PVSLS, such as maintenance, software development, capital replacement, deployment, personnel costs, and capital replacement concerns. There are three basic strategies for implementing PVSLS changes to the PSLs: • Manual implementation. A manually implemented operation requires an operator to change multiple electronic signs when notified, if a condition is observed through live video, or based on other alerts. Crash Type Crash Severity Facility Type Volume Range CMF Standard Error All All Urban Interstate Not specified 0.92 0.04 NOTE: The CMF was developed from data from a single permanent site in Missouri using an empirical Bayes analysis. While the CMF is reliable for the corridor that was studied, analysts should consider whether the results from a permanent installation would be transferable to any specific work zone application. CMF = crash modification factor; PVSLSs = portable variable speed limit systems. Table 2.3. CMFs for PVSLSs.

20 Strategies for Work Zone Transportation Management Plans • Semiautomated implementation. This process would use an algorithm that collects field data (speed, volume, and occupancy) and measures against predetermined thresholds. The operator could be prompted by the software to concur or dismiss suggested changes to the VSL signs. With a semiautomated system, operators could also manually implement changes (i.e., override the system). The algorithm allows different parameters to be set and, depending on the system performance, be adjusted. With a semiautomated system, the software could also prompt operators to approve or dismiss suggested changes (i.e., override the system). • Fully automated implementation. This system has all the capabilities of the previously mentioned systems but does not require any human intervention. A fully automated system would require a considerable amount of time and monetary investment. It would also require extensive instrumentation, stringent maintenance requirements, and testing to ensure the algorithm does not compromise the safety of the traveling public. The following operational parameters should also be considered when deploying PVSLS: • Set minimum frequency for changing speeds at 5 to 10 minutes. Set 5 minutes as the minimum, but the project may consider collecting data using a 10-minute minimum to see if the 5- and 10-minute thresholds are notably different. • Ensure that the PVSLS has a maximum speed limit set for each project and that the maximum speed is the posted speed of the roadway before construction. • Do not reduce speed limits in advance of taper because vehicles may need to accelerate to merge into a single lane of traffic. • Operate the PVSLS only when workers are present and return to PSL when workers are not present. • Use a static sign to advise drivers to return to PSL at the end of the work area. A public information and outreach campaign must also be undertaken before implementation of the PVSLS. 2.2.7 Design Features and Requirements PVSLS typically includes traffic sensors to collect traffic flow and speed data, several properly located electronic speed signs to display speed limits, a reliable control algorithm to compute the optimal set of speed limits at all control locations, a real-time database, and a communication system to convey information between all principal modules. 2.2.8 State of the Practice The following states use VSLs during incident- or weather-related scenarios: Alabama, Delaware, Florida, Georgia, Maine, Maryland, Michigan, Missouri, Nevada, New Jersey, New York, Oregon, Pennsylvania, South Carolina, South Dakota, Tennessee, Texas, Virginia, and Washington. Maryland, Michigan, Minnesota, Virginia, and Texas have used PVSLS on demonstration projects in work zones, but their programs are currently inactive. At the time this guidebook was written, Utah, Colorado, and South Dakota were the only states actively pursuing the use of PVSLS in work zones. The following is a brief description of their programs. 2.2.8.1 Utah UDOT initiated its PVSLS program in 2014, with the assistance of an FHWA Accelerated Innovation Deployment demonstration grant. In 2015, UDOT developed a concept of operations

Work Zone Safety Management Strategies 21 that summarized the PVSLS operational parameters and limits, user and system needs, stake- holder 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). Based on the positive results from the four trial projects, UDOT created a standard drawing (Figure 2.7 and Appendix B) to help contractors to bid and deploy a PVSLS system. At the time this guidebook was written, UDOT has advertised PVSLS for three work zones for the 2019 construction season. 2.2.8.2 Colorado CDOT developed its PVSLS concept of operations in June 2018 and deployed its first PVSLS on an 18-mi stretch of Interstate 25 from south of Castle Rock to Monument, referred to as “the Gap.” It is the only four-lane section of I-25 connecting Colorado’s two largest cities, Denver and Colorado Springs. CDOT deployed 22 electronic speed trailers (11 in each direc- tion) in July 2019. Traffic conditions are monitored at the project operation center and the PVSLS adjusted based on weather conditions, crashes, congestion, or other construction- related effects. Figure 2.8 shows a screenshot of the software used to control the PVSL. These PVSLSs are enforceable and CDOT has partnered with the Colorado State Patrol to signifi- cantly expand traffic enforcement. CDOT has plans to evaluate the effectiveness of the PVSLS in 2020. 2.2.8.3 South Dakota The South Dakota DOT (SDDOT) deployed a PVSLS as part of the I-229, exit 5, reconstruc- tion project in Sioux Falls. The PVSLS was deployed in April 2019 and consisted of 17 electronic speed limit signs tied to a queue warning system (QWS) in advance of the work zone. When the QWS discovers slowed or stopped traffic, it lowers posted speeds for approaching traffic on the electronic speed limit signs, as well as displays an appropriate message on message boards. The PVSLS was incorporated into the QWS through a construction change order. 2.2.9 Cost The cost for deploying a smart work zone such as the PVSLS depends greatly on the project duration and the number of devices (e.g., message boards, traffic sensors, speed trailers, cameras) used. In general, the rental cost is the same for a PCMS or a traffic sensor or camera— approximately $1,000/week/unit. For longer-duration projects, the rental costs can be substan- tially lower. Equipment rental cost for the UDOT PVSLS was between $173 and $329 per day. In addition to the cost of renting the equipment, system deployment budgets were required to address equip- ment mobilization, training, and software configuration. It was determined that a 0.5 full-time equivalent of a field worker’s time is needed to ensure the system transitions in parallel with construction activities. The CDOT PVSLS deployment cost was about $550 per unit per month, with a one-time mobilization fee of $10,000. The SDDOT reported a cost of about $5,700 per each sign along with a monthly maintenance fee of about $1,700 for software and modems.

Figure 2.7. UDOT PVSLS standard drawing (Credit: UDOT).

Work Zone Safety Management Strategies 23 2.2.10 Resources and References Edara, P., C. Sun, and Y. Hou. Evaluation of Variable Advisory Speed Limits in Work Zones. Midwest Smart Work Zone Deployment Initiative, Iowa Department of Transportation. InTrans Project 06-277, August 2013. Enterprise Pooled Fund Study, Variable Speed Limits in Work Zones: Summary of Uses and Benefits, June 2014. Fudala, N. J., and M. D. Fontaine. Work Zone Variable Speed Limit Systems: Effectiveness and System Design Issues, Virginia Transportation Research Council, Virginia Department of Transportation, FHWA/VTRC 10-R20, March 2010. Hines, M., and J. B. McDaniel. NCHRP Legal Research Digest 47: Judicial Enforcement of Variable Speed Limits, TRB, National Research Council, March 2002. Katz, B., J. Ma, H. Rigdon, K. Sykes, Z. Huang, and K. Raboy. Synthesis of Variable Speed Limit Signs, U.S. DOT, FHWA-HOP-17-003, May 2017. Katz, B., C. O’Donnell, K. Donoughe, J. Atkinson, M. Finley, K. Balke, B. Kuhn, and B. Warren. Guidelines for the Use of Variable Speed Limit Systems in Wet Weather, U.S.DOT, FHWA-SA-12-022, August 2012. Kuhn, B., K. Balke, R. Brydia, L. Theiss, I. Tsapakis, L. Ruback, and M. Le. Evaluation of TxDOT Variable Speed Limit Pilot Projects, Texas Department of Transportation. June 2015. Kwon, E., D. Brannan, K. Shouman, C. Isackson, and B. Arseneau. Development and Field Evaluation of Variable Advisory Speed Limit System for Work Zones. Transportation Research Record: Journal of the Transportation Research Board, No. 2015, 2007, pp. 12–18. Lin, P-W, K-P Kang, and G-L Chang. Exploring the Effectiveness of Variable Speed Limit Controls on Highway Work- Zone Operations, Intelligent Transportation Systems, 8:1–14, 2004. ISSN: 1547-2450 print/1547-2442 online. MDOT. Field Test of Variable Speed Limits in Work Zones (in Michigan), Final Report RC-1467. Michigan Department of Transportation, September 2003. Park, S. Y. and Chang, G-L. Applying ITS Technologies to Contend with Highway Congestion: Part-I: Variable Speed Limit Control for Recurrent Congestion, Maryland State Highway Administration (MDSHA), MD-10- SP608B4J, December 2010. Riffkin, M., T. McMurtry, S. Heath, and M. Sait. Variable Speed Limit Signs Effects on Speed and Speed Variation in Work Zones, Utah Department of Transportation Research and Innovation Division Report, No. UT-08.01, January 2008. Saito, M., and A. B. Wilson. Evaluation of the Effectiveness of a Variable Advisory Speed System on Queue Mitigation in Work Zones, Utah Department of Transportation, UT-11.04, August 2011. UDOT. Use of Portable and Dynamic Variable Speed Limits in Construction Zones, Utah Department of Trans- portation, February 2018. https://trid.trb.org/view/1494491. UDOT. Use of Variable Speed Limits in Construction Zones: Concept of Operations, Utah Department of Trans- portation, December 2015. Figure 2.8. Screenshot of software used to control the PVSL (Credit: CDOT).

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) refers to the use of transverse rumble strips in advance of work zones to alert drivers of conditions. TRSs are installed in work zones, are typically temporary, and are removed once the construction is complete. Two kinds of TRSs are available: 1. Portable plastic rumble strips that stay in place under their own weight and do not require the use of nails, adhesives, or fasteners. These strips are black. Figure 2.9 shows an example of portable plastic rumble strips. 2. Orange polymer rumble strips with preapplied adhesive. Figure 2.10 shows an example of this kind of rumble strip. 2.3.2 When to Use States currently use TRSs on both freeway and nonfreeway projects in situations such as lane closures, speed reductions, flagging operations, changes in alignment, new merge patterns, Figure 2.9. Portable plastic rumble strips (Credit: Texas A&M Transportation Institute). Figure 2.10. Orange polymer rumble strips with adhesive (Credit: MDOT).

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. In accordance with the TxDOT Work Zone Temporary Rumble Strip Standard Sheet Memo (November 12, 2012), portable plastic rumble strips are to be used on • One-lane, two-way operations using flaggers, portable signals, or AFADs with a PSL of 70 mph or less, or • Lane closures on conventional highways with a PSL of 70 mph or less. In accordance with the VDOT Revised Guidelines for the Use of Portable Temporary Rumble Strips (IIM-TE-386.1 October 2018), TRSs can be used only when the following conditions are met concurrently: • Work operations involving flaggers, portable signals, or AFADs occur on a two-lane roadway during daylight hours. • Work duration of the activity at a location is greater than 3 hours. • Existing posted or regulatory speed limit is 35 mph or greater. • Roadway has a marked centerline, indicating at least 500 vehicles per day (vpd). Effective January 2020, WisDOT requires TRSs for all flagging operations, static or moving, in place for longer than 2 hours. MDOT allows the use of portable plastic rumble strips on all nonfreeway projects, with a speed limit of 65 mph or less, with traffic regulators or temporary portable signal installations used to regulate traffic (Appendix C1). MDOT also developed two specifications for orange polymer with preapplied adhesive rumble strips, depending on their installation site: (1) one set of specifications detailing the rumble strips’ application in advance of a STOP condition (Appendix C2), and (2) the other set when the strips are used at the approach to a work zone (Appendix C3). TRSs should not be used on fresh seal coats, bleeding asphalt, soft pavement, heavily rutted road, or gravel surfaces. TRSs should also not be used in horizontal curves or on steep slopes. These conditions could cause excessive movement that could lead to a safety hazard for motorists. The duration of the work zone is a key variable in deciding whether to use TRSs and, if so, which type. • Mobile or short-duration work that moves intermittently or continuously: TRSs are not practical. • Short-term stationary work (>1 hour within a single daylight period): portable plastic rumble strips are best suited. • Intermediate-term stationary work (>1 daylight period up to 3 days, or nighttime work >1 hour): portable plastic rumble strips are best suited. • Long-term stationary work (>3 days): portable plastic rumble strips or polymer/thermoplastic with preapplied adhesive are best suited. 2.3.3 Benefits The use of TRSs provides the following benefits: • The sight of rumble strips can alert motorists that they are about to enter a work zone where unusual or unexpected road conditions exist. • Audible and vibratory stimuli produced by rumble strips can increase awareness among drivers as they travel through work zones, which can be particularly helpful for inattentive,

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. 2.3.4 Expected Effectiveness Nearly all rumble strip research reported an increase in driver awareness. Some findings include the following: • 1 to 7.2 mph reduction in average speeds (WisDOT 2018). • 10.1 percent–13.8 percent reduction in mean speeds and 8.3 percent–14.5 percent reduction in the 85th percentile speeds (Yang et al. 2013). • 0.39 to 1 mph reduction in average speeds (Sun, Edara, and Ervin 2011). • 4.6 to 11.4 mph mean speed reduction for automobiles and 5 to 11.7 mph for trucks (Wang et al. 2011). • 1 to 2 mph reductions in mean speed (Fitzsimmons et al. 2009). • 8 mph reduction in mean speed (Reddy et al. 2008). • 2 mph mean reduction in automobile speeds and 7.2 mph for truck speeds (Fontaine and Carlson 2001). 2.3.5 Crash Modification Factor Table 2.4 shows the CMF for TRSs. Chapter 13 provides additional information on devel- oping WZCMFs. 2.3.6 Implementation The following aspects should also be considered when deploying TRSs: • TRSs do not provide drivers any indication of what action is desired. Thus, deploy TRS only in conjunction with other TCDs that help drivers identify the appropriate action. • To make cyclists, motorcyclists, and motorists aware that the TRSs are deliberate, and to prevent erroneous drivers’ responses, place a RUMBLE STRIPS AHEAD warning sign in advance of zones where TRSs are present. • TRS can cause stability problems for motorcyclists and bicyclists. Provide breaks in the center of the lane to allow motorcycles and bicycles to avoid them if so desired. Advance warning about the presence of TRSs is also useful. The 2009 MUTCD includes a motor- cycle plaque (W8-15P) that may be mounted below a warning sign indicating loose gravel, grooved pavement, metal bridge deck, or steel plates ahead if the warning is intended to be directed primarily to motorcyclists. In response to specific requirements enacted through the Crash Type Crash Severity Facility Type Volume Range (AADT) CMF Standard Error Nighttime All Rural Interstate when queues were not present 55,000– 110,000 0.890 (not significant) 0.377 Nighttime All Rural Interstate when queues were present 55,000– 110,000 0.397 0.265 NOTE: AADT = annual average daily traffic; CMF = crash modification factor; TRS = temporary rumble strip. Table 2.4. CMFs for TRSs.

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) to be used in conjunction with other warning signs in advance of hazards to reduce motorcycle risks in work zones. • Extend TRSs onto the shoulder to discourage drivers from making erratic maneuvers to avoid the strips. • Avoid placing TRSs on sharp horizontal or vertical curves, soft fresh seal coat, or heavily rutted pavement. • TRS maintenance is crucial in ensuring intended performance. Immediately replace shifting or misaligned rumble strips. 2.3.7 Design Features and Requirements The configuration of TRSs includes interrelated factors such as their placement within the work zone, number of arrays (or sets) of TRSs used at a work zone, number of strips in a set, and spacing of strips in the set. TRSs have been tested or deployed for use in work zones in patterns ranging from 1 to 25 rumble strips, with 6 strips being a frequently used pattern in evaluations. There is a variety of practices or recommendations regarding the configuration of TRSs. Practitioners should ultimately follow state DOT specifications, traffic control plans, and manufacturer recommendations, when available. Table 2.5 provides a sample of rumble strip configurations currently used in work zones. 2.3.8 State of the Practice TRSs are widely used by several states that have developed their own standard specifications and traffic control plans. Examples of standard drawings from selected state DOTs are provided. • Appendix C1 presents the MDOT special provision for TRSs (March 2018). • Appendix C2 presents the MDOT special provision for TRSs (orange) in advance of a stop condition (February 2012). • Appendix C3 presents the MDOT special provision for TRSs (orange) in advance of a work zone (February 2012). • Appendix C4 presents the UDOT standard drawings for use of TRSs for freeway/divided- highway lane and shoulder closures (June 2018). • Appendix C5 provides the CDOT portable TRS typical applications for use with one-lane, two-way operations using flaggers and for lane closures on multilane divided highways (revised May 2018). State <40 mph 40–49 mph ≥50 mph Ohio 6–8 6–8 6–8 Texas 10a 15b 20c Virginia 10 15 20 Iowa 10–20 10–20 10–20 Utah 40 40 40 Colorado 40 40 40 NOTE: ᵃ ≤40 mph ᵇ >40 mph and ≤55 mph c >55 mph Information obtained from review of state manuals and typical applications. PSL = posted speed limit. TRS = temporary rumble strip. Table 2.5. TRS spacing (in ft) by PSL.

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). Portable plastic rumble strips are reusable and normally last 3 to 5 years, depending on use. 2.3.10 Resources and References American Traffic Safety Services Association. Guidance for the Use of Temporary Rumble Strips in Work Zones. 2013. Ezekiel, Y., G. L. Hsieh, G. P. Ullman, and R. E. Brydia. Effectiveness of End-of-Queue Warning Systems and Portable Rumble Strips on Lane Closure Crashes. Journal of Transportation Engineering, ASCE, Part A: Systems Vol. 143, Issue 11 (November 2017). Finley, M. D., J. D. Miles, and P. J. Carlson. An Assessment of Various Rumble Strip Designs and Pavement Marking Applications for Crosswalks and Work Zones, Texas Department of Transportation, FHWA/TX-06/0-4728-2, October 2005. Fitzsimmons, E., N. Oneyear, S. Hallmark, N. Hawkins, and T. Maze. Synthesis of Traffic Calming Techniques in Work Zones. Iowa State University. January 2009. Fontaine, M. D., and P. J. Carlson. Evaluation of Speed Displays and Rumble Strips at Rural-Maintenance Work Zones. Transportation Research Record: Journal of the Transportation Research Board, No. 1745, 2001, pp. 27–38. Horowitz, A. J., and T. Notbohm. Testing Temporary Work Zone Rumble Strips. Ames, IA: Institute for Trans- portation, Iowa State University (Midwest Smart Work Zone Deployment Initiative), 2005. Manual on Uniform Traffic Control Devices. FHWA, U.S. DOT, 2009. http://mutcd.fhwa.dot.gov/. [MUTCD] Reddy, V., D. Tapn, D. McAvoy, and S. Pinapaka. Evaluation of Innovative Safety Treatments—A Study of the Effectiveness of Temporary Rumble Strips in Construction Work Zones. Florida Department of Transportation, 40502-PL-008-001, January 2008. Schrock, S. D., V. R. Sarikonda, and E. J. Fitzsimmons. Development of Temporary Rumble Strip Specifications, Kansas Department of Transportation (K-TRAN: KU-14-6), February 2016. Sun, C., P. Edara, and K. Ervin. Elevated-Risk Work Zone Evaluation of Temporary Rumble Strips. Missouri Department of Transportation, K-TRAN: KU-09-5. December 2011. Virkler, M. Removable Orange Rumble Strips. University of Missouri, 2000. Virkler M., M. Deepak, and K. L. Sanford Bernhardt. Preformed Rumble Strips. University of Missouri, 2002. Wang, M. H., S. D. Schrock, Y. Bai, and R. A. Rescot. Evaluation of Innovative Traffic Safety Devices at Short-Term Work Zones, Kansas Department of Transportation. K-TRAN: KU-09-5. December 2011. WisDOT. Temporary Portable Rumble Strips Study, Wisconsin Department of Transportation, Bureau of Traffic Operations, January 2018. Yang, H., K. Ozbay, B. Bartin, and S. Chien. Evaluation of Supplementary Traffic Control Devices for Surveyor Safety Enhancement. Presented at 92nd Annual Meeting of the Transportation Research Board, Washington, D.C., 2013. 2.4 Sequential Flashing Warning Lights 2.4.1 Description Sequential flashing warning lights (SEQ) are wireless steady-burn warning lights, mounted on channelizing devices and flashing in a sequence to clearly delineate the taper at work zone lane closures (Figure 2.11). To help drivers identify the required vehicle path, the successive flashing of the SEQ begins at the upstream end of the merging taper and ends at the downstream end of the merging taper. 2.4.2 When to Use SEQ use is restricted to nighttime work zones with lane closures only. The North Carolina DOT (NCDOT) allows the use of SEQ for merging tapers during nightly work activities on Interstates and freeways with speed limits greater than 55 mph and facilities with significant traffic volumes.

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. MoDOT has also deployed SEQ on nighttime Interstate construc- tion and maintenance projects. 2.4.3 Benefits The use of SEQ provides the following benefits: • Improving driver recognition of merging taper, • Increasing drivers’ awareness of active work zones, • Reducing driver approach speeds, • Maximizing traffic flow by promoting smooth lane merges, • Reducing the incidence of last-second decisions in a taper merge maneuver (i.e., better and earlier lane discipline), and • Offering a low-cost countermeasure with potential high returns. 2.4.4 Expected Effectiveness Field evaluations of SEQs have reported the following results: • Average speeds decreased on average by 2.2 mph and 85th percentile speeds decreased on average by 1 mph, which causes vehicles to merge further upstream from the taper. The benefit–cost ratio ranged from 5 to 10 (Sun et al. 2011). • A Texas Transportation Institute study reported a “one-fourth reduction in the number of passenger vehicles and a two-thirds reduction in the number of trucks in the closed lane 1,000-ft upstream of the lane closure” (Finley, Ullman, and Dudek 2001). • A British Highways Agency study (2005) reported that the “effect of sequential lamps is seen consistently from a point 500 m before the taper, but also has an effect at a point 600 m before the taper in half the cases.” 2.4.5 Crash Modification Factor No CMF is available for this strategy. Figure 2.11. Sequential warning lights (Credit: University of Missouri).

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. The number of SEQs deployed on a project depends on the PSL and the number and spacing of channelizing devices. The number of lights used in the drum taper must equal the number of drums used in the taper. If only one or two units are knocked out or not working, the flashing sequence should continue. If more than three units are not working, all lights should be automatically turned off. Nonsequential flashing is prohibited. The SEQ must be deactivated when lane closures are not in effect. One potential drawback is that a small percentage of drivers became more aggressive when overtaking at the taper because the taper becomes more visible. 2.4.7 Design Features and Requirements The SEQ must comply with the 2009 MUTCD, as defined in Section 6F.63, Channelizing Devices, and Section 6F.83, Warning Lights. Section 6F.83 further states that “each flashing warning light in the sequence shall be flashed at a rate of not less than 55 or more than 75 times per minute.” CDOT specifies “the size of each lens to be 7 in. in diameter, each lamp to have a low output steady Type C backlight to aid direction indication, utilize intelligent wireless communications and be certified as crashworthy Category 1.” 2.4.8 State of the Practice At the time this guidebook was written, Missouri and North Carolina were the only states actively pursuing the use of SEQs in work zones. The Oklahoma Department of Transportation (OKDOT) deployed SEQ as part of the AASHTO Innovation Initiative in 2011; however, its program ended in 2012 and at the time this guidebook was written, OKDOT was no longer deploying SEQ. 2.4.8.1 Missouri The AASHTO Innovation Initiative identified MoDOT as one of the lead states for experi- mental deployments. Since then, MoDOT has expanded its program and, at the time this guidebook was written, has used SEQ on more than 100 projects. MoDOT developed guidance for using SEQ in its Engineering Policy Guide (Section 616.6.83), which Figure 2.12 shows. 2.4.8.2 North Carolina The NCDOT used SEQ on the following two projects in Forsyth and Davie Counties: • I-0911A (Widen I-40 from Harper Road in Forsyth County to NC 801 in Davie County). • I-5823 (I-40 pavement rehabilitation from US 601 in Davie County to Iredell County line). 2.4.9 Cost Typical cost for SEQ is $150 per each light.

Work Zone Safety Management Strategies 31 Figure 2.12. MoDOT SEQ guidance (Credit: MoDOT).

32 Strategies for Work Zone Transportation Management Plans 2.4.10 Resources and References Finley, M. D., G. L. Ullman, and C. L. Dudek. Sequential Warning-Light System for Work-Zone Lane Closures. Transportation Research Record: Journal of the Transportation Research Board, No. 1745, 2001, pp. 39–45. Highways Agency. Evaluation of Sequential Flashing Cone Lamps. Trial Team: First Annual Report, Department of Transport, London, 2005. Manual on Uniform Traffic Control Devices. FHWA, U.S. DOT, 2009. http://mutcd.fhwa.dot.gov/. [MUTCD] Rea, M. S., J. D. Bullough, L. C. Radetsky, N. P. Skinner, and A. Bierman. “Toward the Development of Standards for Yellow Flashing Lights Used in Work Zones,” Lighting Research & Technology, 50: 552–570, The Society of Light and Lighting, 2018. Sun, C., P. Edara, Y. Hou, and A. Robertson. Evaluation of Sequential Warning Lights in Nighttime Work Zone Tapers. University of Missouri—Columbia. 2011. 2.5 Automated Flagger Assistance Devices 2.5.1 Description Automated flagger assistance devices (AFADs) are TCDs that enable flaggers to be positioned out of the lane of traffic and that are used to direct traffic at lane closures on two-lane, two-way roadways. The 2009 MUTCD includes two basic types of AFADs: (1) a remotely controlled STOP/SLOW sign mounted on a trailer or moveable cart and (2) a remotely controlled red/yellow lens with a mechanically gated arm (Figure 2.13). 2.5.2 When to Use AFADs are only to be used where there is only one lane of approaching traffic in the direc- tion to be controlled. Most states permit use of AFADs during daytime or nighttime operations; however, if used at night, the AFADs should be illuminated in accordance with the 2009 MUTCD (Section 6E.08). AFADs are typically used for short-term or intermediate-term lane or road closures, such as bridge maintenance, haul road crossings, guardrail repair, and pavement patching, when a flagger would normally be used. Their use is discouraged during long-term closures. DOTs have successfully implemented AFADs on roads with a wide range of average daily traffic (ADT) counts. Although the 2009 MUTCD does not provide any limitations in this area, some states have established supplementary guidelines. For example, VDOT allows AFADs in temporary lane closures on two-way roads when the ADT is below 12,000 vpd, whereas Minnesota restricts the use of AFADs to roads with less than 1,500 ADT. Figure 2.13. Examples of STOP/SLOW (left) and red/yellow (right) AFADs (Credit: FHWA).

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. According to a Virginia study, drivers were confused when the STOP/SLOW version was accompanied by signs reading WAIT ON STOP and GO ON SLOW. Many drivers interpreted them to mean they should pause at the STOP sign before proceeding slowly, rather than wait until the sign changed to SLOW before moving (Cottrell 2006). There were significantly more violations of the STOP/SLOW version in Texas than of the red/yellow lens version, although STOP/SLOW violations dropped to levels similar to the red/yellow lens when a mechanical gate arm was added to the device (Finley 2013). Surveys of work zone crews in Maine, Missouri, and Virginia have found enthusiastic approval of AFADs (ATSSA 2012). 2.5.5 Crash Modification Factor No CMF is available for this strategy. 2.5.6 Implementation Considerations While AFADs are a method of improving the safety of flagging operations, they do not eliminate the need for trained flaggers. AFAD operators must be certified flaggers trained on operating the device correctly; the operator must be able to manually control the lane closure in the event an AFAD malfunctions. It is preferable to place the AFAD within the shoulder of the road; however, if the shoulder is not adequate, the AFAD is permitted to encroach on the travel lane, provided the appropriate sight distance is available. If this is the case, the gate arm must not extend into the adjacent lane. Most states limit the distance between flagging stations to 800 ft, although some (e.g., Minnesota) permit their use in 1,000-ft work zones if each device has its own operator. On work zones with a long activity area, intermediate regulators need to know the direction of traffic flow, especially for traffic on side roads. 2.5.7 Design Features and Requirements All AFAD applications must abide by the specific standards set forth in the MUTCD (Section 6E.04). Section 6E.05 provides detailed specifications for STOP/SLOW AFADs; similarly, Section 6E.06 lists detailed specifications for red/yellow AFADs. In accordance with NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features (Ross, Sicking, and Zimmer 1993) and the AASHTO Manual for Assessing Safety Hardware, AFADs must satisfy applicable crashworthiness standards based on device weight. There are two methods for using AFADs in a work zone. The first method employs an AFAD at each end of the work zone; the second method employs an AFAD at one end and a flagger at the other end. Two separate flaggers are commonly used to operate in either method; however, a single flagger may remotely control two flagging stations, provided that the flagger has a clear view of each station and of approaching traffic in both directions. In accordance with

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. When an AFAD is used, the advance warning signing should include a ROAD WORK AHEAD (W20-1) sign, a ONE LANE ROAD (W20-4) sign, and a BE PREPARED TO STOP (W3-4) sign. 2.5.8 State of the Practice Currently, 11 states have standards for using AFADs: Alabama, Florida, Illinois, Kansas, Minnesota, North Carolina, Ohio, Oregon, Virginia, Washington, and Wisconsin. MoDOT developed a new AFAD system that uses STOP/SLOW paddles and flashing red/yellow lights (Brown et al. 2018). In addition, a changeable message sign (CMS) was installed to display a series of four messages. As Figure 2.14 shows, the CMS alternated between an image of a STOP sign and the word STOP every 2 seconds during the stopped interval. The CMS alternated between an image of SLOW and the words GO ON SLOW every 2 seconds during the GO interval. The AFAD was built onto a truck-mounted attenuator (TMA) unit. The truck integration obviates the need to tow and deploy trailer-mounted AFADs. 2.5.9 Cost The average cost for AFADs ranges between $25,000 and $30,000, excluding flagger costs. Rental prices vary between $3,000 and $3,500 per month, but these rates vary by geographic location, season, and number of units rented. 2.5.10 Resources and References Brown, H., C. Sun, S. Zhang, and Z. Qing. Evaluation of Automated Flagger Assistance Devices. Missouri Depart- ment of Transportation. February 2018. Figure 2.14. Missouri AFAD with changeable message sign (Credit: University of Missouri).

Work Zone Safety Management Strategies 35 Cottrell B. H., Jr. Evaluation of the AutoFlagger in Virginia, Report Number VTRC 07-R12, Virginia Trans- portation Research Council, Charlottesville, Virginia, 2006. Finley, M. Field Evaluation of Automated Flagger Assistance Devices in Work Zones on Two-Lane Roads. Transportation Research Record: Journal of the Transportation Research Board, No. 2337, 2013, pp. 1–8. Finley, M., B. Ullman, N. Trout, and E. Park. Studies to Determine the Effectiveness of Automated Flagger Assistance Devices and School Crossing Devices. Report No. FHWA/TX-12/0-6407-1. Texas Department of Trans portation, 2012. Guidance on the Use of Automated Flagger Assistance Devices, ATSSA (American Traffic Safety Service Asso- ciation), 2012. Manual for Assessing Safety Hardware, 2nd ed. AASHTO, Washington, D.C., 2016. [MASH16] Manual on Uniform Traffic Control Devices. FHWA, U.S. DOT, 2009. http://mutcd.fhwa.dot.gov/. [MUTCD] MoDOT. Evaluation of Automatic Flagger Assistance Devices, Missouri Department of Transportation Orga- nizational Results Division, 2008. MoDOT. Lane Closure on Two-Lane Highways Using Automated Flagger Assistance Devices (AFAD) with Red and Amber Signal System, Missouri Department of Transportation, 2012. Odell, W. Automated Flagger Assistance Devices (AFADs): Saving Lives. Presented at 92nd Annual Meeting of the Transportation Research Board, Washington, D.C., 2013. Ross, H. E., Jr., D. L. Sicking, and R. A. Zimmer. NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features. TRB, National Research Council, Washington, D.C., 1993. 2.6 Work Zone Intrusion Alarm 2.6.1 Description A work zone intrusion alarm (WZIA) is equipment that provides highway workers with additional warning of unauthorized vehicles and errant motorists that enter a work zone. WZIA uses vehicle-detection technology and audible, visual, or tactile alarms to alert workers to intrusions while giving them enough reaction time to move away from the hazardous location. The first WZIAs were developed under the Strategic Highway Research Program and used microwave, infrared, and pneumatic tubes for vehicle detection. Most previous WZIAs have been decommissioned for several reasons, including low demand (small market), persistent false alarms, high cost, difficulty to deploy, and limited range of alarm. Since the development of these first-generation WZIAs, manufactures have used other technologies to develop other similar devices. The COTS WZIAs, available at the time of this writing, are described here and shown in Figure 2.15. • Worker Alert System (WAS), by Astro Optics, LLC, is a pneumatic microwave-based system with an auditory, visual, and haptic alarm that is wirelessly triggered when a vehicle crosses over a pneumatic hose positioned in a work zone. The audio alarm is 80 dB at 50 ft. • SonoBlaster, by Transpo Industries, is a kinematic system comprising of a disposable carbon dioxide (CO2) cartridge and an alarm unit. When the CO2 cartridge is punctured, the escaping gas produces sounds through an air-pressure horn. The device can be mounted on traffic cones, drums, delineators, and other barricades. The audio alarm is 90 dB at 50 ft. • Intellicone, by Highway Resource Solutions (United Kingdom), is a lamp-integrated motion sensor attached to a traffic cone that can detect being hit by a vehicle and when vehicles cross between cones. When triggered, the unit signals a visual and a three-tone audio alarm. Intellicone also wirelessly sends an alert to a web portal to enable automated online reporting (communication features are currently unavailable in the United States). The audio alarm is 75 dB at 50 ft. 2.6.2 When to Use WZIA should be used primarily where adding a positive protection system such as concrete barrier is not feasible, worker safety is of particular concern, crash rates upstream of the merge

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. 2017) recommended • Intellicone for work zones longer than 1 day, tapers longer than or equal to 1,500 ft, or both. • WAS for work zones less than 1 day, tapers shorter than or equal to 1,500 ft, or both. 2.6.3 Benefits Intrusion alarms improve safety by allowing workers time to move out of harm’s way from an errant vehicle, reducing the potential for a work zone vehicular related injury. 2.6.4 Expected Effectiveness Limited studies have been conducted to evaluate and compare the available WZIA tech- nologies, as the following describes. • WAS. Gambatese, Lee, and Nnaji (2017) evaluated the effectiveness of WAS, SonoBlaster, and Intellicone on three paving projects over 10 weeks. The study found the duration of the WAS alarm to be consistently 6 seconds. WAS produced the loudest sound when the alarm was oriented toward the sound meter. A lag time of no more than 1 second was observed between the time the pneumatic tube is pressured and the alarm is triggered. The indistinct alarm was a concern because it might not alert workers working closely to noisy equipment. • SonoBlaster – A study conducted by Novosel (2014) for the Kansas DOT (KSDOT) found the SonoBlaster alarm duration to be inconsistent, ranging from 3 to 80 seconds. Irrespective of the orientation, the peak sound level occurred within the first second of firing and subsequent sound levels dropped off unevenly. A major concern with the SonoBlaster system was that in cold weather and after the first activation, the compressed CO2 cartridge can become cold enough during firing that ice condenses on the cartridge. Novosel found that accumulated ice between the CO2 cartridge and the firing pin prevented the system from working properly. Furthermore, replacing the CO2 cartridge in cold or wet weather may bring moisture in contact with the nozzle. Figure 2.15. Commercially available WZIA systems (Credit: Caltrans).

Work Zone Safety Management Strategies 37 – The study conducted by Gambatese, Lee, and Nnaji (2017) found similar results to the Novosel study. The SonoBlaster yielded false negatives (i.e., the system triggered but the alarm did not activate) and produced shorter bursts of sound after it had been used and the cartridge had been replaced. – FHWA disseminated SonoBlaster intrusion alarm devices to several states for a demonstra- tion project (Kuta 2009). The demonstration participants began field-testing the units in 2008. FHWA synthesized the evaluations (forms, e-mailed comments, or phone calls) into a demonstration project interim report issued in July 2009. The evaluations led to retooling the device to improve sound, set up, and mounting aspects. FHWA then made the retooled units available to original and new participants for testing and evaluation. – The New Jersey Department of Transportation (NJDOT) was one of the state agencies nationwide to test the SonoBlaster. NJDOT used a retooled version of an earlier unit dis- tributed by FHWA. Problems with quality control and reliability, combined with the cost of the alarm, raised doubts about the desirability of and potential benefits to be gained from deploying the device on NJDOT maintenance jobs. The NJDOT decision was that conducting additional test deployments would not substantially change the conclusions. • Intellicone. Gambatese, Lee, and Nnaji (2017) found the sound to be louder when two speakers were oriented toward the sound meter. The maximum range between a lamp and the alarm was 250 feet, and the alarm duration was consistent at 32 seconds. Similarly, Novosel (2014) found that even though engine and mechanical noises from construction vehicles in a work zone were louder than the Intellicone alarms, the sound could be distinguished because of its high frequency and three tones (Novosel 2014). However, distinguishing the alarm sound from the inside of a work zone vehicle (a backhoe) at 100 to 200 feet away was difficult. The maximum sound level was around 90 dB at 10 feet and decreased to around 55 to 60 dB at 400 feet. Workers found the audible alarm on the Intellicone system difficult to hear because of its low volume (Novosel 2014). In addition to the COTS available technologies, some prototype WZIAs were developed and tested as follows: • Hayden (2013) evaluated the sDrum system effectiveness and deployment. The system consists of 28 orange traffic drums (called smart drums or sDrums) positioned adjacent to the orange cones marking the work zone lane closure. When the system detects a speeding vehicle approaching, the orange lights on top of the drums produce synchronous flashes that warn the driver to slow down and alert workers of a speeding vehicle. If the vehicle speed is above a set trigger speed, the system activates a pager system that warns the workers of the speeding vehicle. A Caltrans research team deployed the pilot system for 4 weeks near Los Banos with inconclusive results. • Hourdos (2012) developed and tested a low-cost rapidly deployable intelligent drum line prototype that sends an audible warning to alert motorists traveling at dangerous speeds near highway work zones. The intelligent drum line system is comprised of two instrumented work zone drums. The sensor subsystem measures the speed of the oncoming vehicles and detects the location of the vehicle with respect to each drum. The audible warning system is comprised of a powerful air horn mounted inside the drum and designed to direct the sound force mainly toward the roadway; sound is suppressed in all other directions. Researchers tested the system only under simulated conditions and not in conjunction with actual work zone operations. 2.6.5 Crash Modification Factor No CMF is available for this strategy.

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. Sound alarms produced by the work zone intrusion alert technology should be at least 110 dB when the alarm is located 50 ft away from workers and above 95 dB when the alarm is 100 ft away. Researchers preferred types of sounds, such as a screeching noise or one emitted by an emergency vehicle siren, that differ from the noises heard during the opera- tion (e.g., diesel engine noise from equipment, truck backup alarm, passing automobile). In addition, agencies should avoid short-burst alarms. Alarms that provide longer, continuous sound improve the possibility of capturing workers’ attention. • Transmission distance. The minimum transmission distance should be 400 ft when the 85th percentile work zone speed is 35 mph. For work zones with historically higher vehicle travel speed, higher maximum work zone speed limits, and greater expected distances between workers, the transmission distance can be increased. • Haptic alarms. Any haptic or vibration feature included with the alarm technology should be mobile, portable, and wearable either on the worker’s arm or on the hard hat. A patterned vibratory signal lasts for approximately 14 seconds and creates a vibration frequency of 150 Hz. 2.6.7 Design Features and Requirements The California Department of Transportation (Caltrans) conducted pilot testing of WAS, SonoBlaster, and Intellicone systems at its Maintenance Equipment Training Academy testing facility, which is a controlled environment (closed to live traffic). All tests were conducted in November 2018 (Task Number 3038, Evaluation of Work Zone Intrusion Alarms). Based on the results of operational and range tests conducted, Caltrans developed recom- mended deployment plans for WAS (Figure 2.16) and Intellicone (Figure 2.17). Figure 2.16 shows recommended and maximum distance between components of the WAS at which the evaluation trials produced 100 percent successful results. Caltrans recommends a Figure 2.16. Caltrans WAS recommended deployment plan (Credit: Caltrans).

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. Although Figure 2.16 shows three trip hoses, a recommendation on the specific number of trip hoses is not provided since that would depend on the length of the work zone and the number of available devices. Instead, a maximum of 75 feet between the trip hoses is recommended based on discussions and feedback from maintenance workers during supple- mental testing, as this distance provided effective coverage with minimum gaps for intruding vehicles to miss a trip hose. Based on this recommendation, the total number of trip hoses can be calculated given the length of a work zone. It is also recommended to lay out the trip hoses diagonally at an approximate angle of between 45 to 70 degrees to improve the coverage area. Multiple alarm units should be placed, ideally, at the start, middle, and end of the work area, ensuring the maximum distance between the alarm units does not exceed 175 ft with a clear line of sight. Also, the units should be placed at least 4 ft above the ground. The speaker on the alarm unit should be oriented toward the workers during daytime and the light source should be oriented toward the workers during nighttime operations. Figure 2.17 shows Intellicone lamps on the taper and tangent cones with spacing as required by the Caltrans standard traffic control plan tables. The maximum distance between the lamps, between the portable site alarm and the nearest lamp, and between two PSA units must be at most 100 ft, at which the evaluation trials in this research produced 100 percent successful results. For effective coverage, additional cones with lamps are recommended to be deployed transverse to the traffic flow, as shown in Figure 2.17. Two cones are recommended, with a maximum spacing of 5 ft. This configuration should be repeated every 100 ft, starting from the work area and going upstream in the work zone. It is recommended to deploy as many cones with lamps as available to increase the coverage area of the system in a work zone. Based on the work zone speed and spacing between the cones, the number of cones required for a specific work zone can be calculated. Lamps of all sensitivities except “very high” are recommended Figure 2.17. Caltrans Intellicone recommended deployment plan (Credit: Caltrans).

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. The Pennsylvania DOT (PennDOT) also developed WZIA standard drawings for use on conventional highways and on freeways and expressways, as shown in Figure 2.18. 2.6.8 State of the Practice Current literature suggests that work zone intrusion alert systems are not widely used. At the time this guidebook was written, only Pennsylvania had deployed intrusion alarms in active work zones. California and Oregon conducted testing in controlled environments (closed to live traffic) to better understand system deployment, practical implementation, capabilities, and limitations. 2.6.8.1 Pennsylvania PennDOT purchased 16 WASs in 2018 and distributed them to districts for an evaluation that lasted until June 30, 2019. Each PennDOT district was asked to evaluate the system for at least 1 month. Districts with more than six counties were given an extra intrusion alarm to allow all counties to use the devices for at least 1 month. By tracking where and when the devices were used and evaluations by the field staff, PennDOT intends to issue recommenda- tions for further purchases. Figure 2.18. PennDOT-suggested WAS placement (Credit: PennDOT).

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 intro- duced Advanced Warning and Risk Evasion (AWARE) alert technology. The system relies on position and orientation sensors and radar to constantly monitor the work zone. AWARE was piloted during a paving project for the Minnesota Department of Transportation (MnDOT) in May 2018. Overall, the pilot was successful in illustrating the potential of the AWARE system to detect vehicle intrusions into workspaces and to warn both intruding motorists and work crews. The AWARE system is undergoing more field-testing and is not currently commercially available. 2.6.8.3 Minnesota MnDOT has developed a concept of operations for a work zone intrusion warning system to support enhanced work zone safety (MnDOT 2015). The system requirements were derived from the needs identified in the concept of operations and address the functional aspects of the system. Figure 2.19 shows a screenshot of the system requirements. 2.6.9 Cost Caltrans estimated costs for a hypothetical half-mile closure on a two-lane road with 12-ft wide lanes, PSL of 25 mph (channelizing device spacing of 25 ft in taper and 50 in tangent section resulting in a total of 63 channelizing devices), and activity area of 500 ft as follows: • WAS. $4,630 assuming the use of 10 personal safety devices, three alarm units, six 33-ft trip hoses with chargers, and a single handheld remote trigger. • SonoBlaster. $5,670 for 63 units with one CO2 cartridge per unit (or unit price of about $90). • Intellicone. $11,100 for 63 units and two PSAs (or unit price of approximately $150 to $200). Figure 2.19. Minnesota work zone intrusion warning system requirements (Credit: MnDOT).

42 Strategies for Work Zone Transportation Management Plans 2.6.10 Resources and References Brown, H., C. Sun, and T. Cope. “Evaluation of Mobile Work Zone Alarm Systems,” Transportation Research Record: Journal of the Transportation Research Board, No. 2485, pp. 42–50, 2015. Caltrans. Task Number 3038, Evaluation of Work Zone Intrusion Alarms. Division of Research, Innovation and System Information, 2019. Fyrie, P. “Work Zone Intrusion Alarms for Highway Workers,” AHMCT Research Center. University of California at Davis, 2016. Gambatese, J., H. Lee, and C. Nnaji. Work Zone Intrusion Alert Technology: Assessment and Practical Guidelines, Oregon Department of Transportation, 2017. Hayden, L. Pager Performance for the Western Transportation Institute’s Augmented Speed Enforcement Project. California Department of Transportation (Caltrans) Division of Research. CA13-2062E. 2013. Hourdos, J. Portable, Non-Intrusive Advance Warning Devices for Work Zones with or without Flag Operators, University of Minnesota, Minnesota Traffic Observatory, MN/RC 20-26, October 2012. Krupa, C. Work Zone Intrusion Alarm Effectiveness, NJ-2010-004, New Jersey Department of Transportation, September 2010. Kuta, B. Work Zone Intrusion Alarm Demonstration Interim Report—SonoBlaster, FHWA Resource Center, U.S. DOT, August 2009. Marks, E., S. Vereen, and I. Awolusi. “Active Work Zone Safety Using Emerging Technologies 2017,” UTCA Report Number 15412, 2017. MnDOT. Work Zone Intrusion Warning System: System Requirements, Minnesota Department of Transportation, 2015. Novosel, C. Evaluation of Advanced Safety Perimeter Systems for Kansas Temporary Work Zones. Ph.D. dissertation, University of Kansas, 2014. PennDOT. Ways to Stop Work Zone Intrusions, PennDOT District 12, Progress Report, Volume 1, Issue 8, 2018. Theiss, L., G. L. Ullman, and T. E. Lindheimer. Closed Course Performance Testing of the AWARE Intrusion Alarm System, Texas A&M Transportation Institute, College Station, TX, 2017. Ullman, G. L., and L. Theiss. Personal Warning Sensor for Road Construction Worker, Texas A&M Transportation Institute, College Station, TX, 2019. Ullman, G. L., N. D. Trout, and L. Theiss. Driver Responses to the AWARE Intrusion Alarm System, Texas A&M Transportation Institute, College Station, TX, 2016. Zhang, F., and J. Gambatese. “Highway Construction Work-Zone Safety: Effectiveness of Traffic-Control Devices.” Practice Periodical on Structural Design and Construction, 22(4), 04017010, 2017. 2.7 Moveable Traffic Barrier Systems 2.7.1 Description Moveable or mobile traffic barrier systems protect workers by isolating short-duration work zones from live traffic. At the time this guidebook was written, the two tractor trailer– mounted mobile barrier systems used in the United States are the Balsi Beam developed by Caltrans and the proprietary Mobile Barrier Trailer (MBT-1) system developed by Mobile Barriers LLC. 2.7.2 When to Use Short-term freeway maintenance projects, such as shoulder repair, guardrail replacement, bridge deck repairs, bridge joint maintenance, median barrier repair, and pavement patching, that require maintaining high-speed, multilane traffic, are the most common category for potential moveable barrier use. The most common method for using moveable barriers is as a shoulder application. During peak traffic hours, the barrier is on the shoulder protecting equipment, materials, drop-off, and the like, but does not encroach on traffic lanes. During off-peak hours, adjacent lanes can be closed and the moveable barrier positioned into the closed lane to provide a larger protected work area or a work/haul vehicle-access lane.

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. For road crews, the mobile barrier protects against work zone intrusions, reduces the vehicles and equipment otherwise needed on site, and improves lighting and ambient conditions. With less worker fatigue and fewer delays, crews have reported productivity gains of 60 to 80 percent. 2.7.4 Expected Effectiveness Moveable traffic barrier systems have reduced mean speeds by 4 to 6.2 mph (Gambatese and Tymvios 2013). 2.7.5 Crash Modification Factor A CMF is not available for this strategy. 2.7.6 Implementation Considerations Moveable barrier systems should be considered for use in the following situations: • Time-of-day restrictions for lane closures limit available work time. • Work activity is short term or can be broken into a series of short-term closures. • Exposed work hazards require positive protection. In addition, with the barrier in place, limited space is available to travel to and from the work- site on the same side. 2.7.7 Design Features and Requirements 2.7.7.1 Balsi Beam Caltrans developed the tractor trailer–mounted mobile worker protection device Balsi Beam in 2003 (Mortazavi 2010, Figure 2.20). The trailer consists of two telescoping high-strength steel beams whose width can be extended to as much as 12 ft. Using hydraulic power, each beam can rotate to either side of the roadway (left or right), depending on which side requires protection; stacking both beams on the same side will create a 3-ft-high wall. The trailer can be extended to provide a work area up to 30 ft long. The trailer beams act as a rigid obstacle that deflects any vehicle that attempts to penetrate the work area from the side; a TMA is attached to the rear of the trailer. NCHRP Report 350 Level 2 crash testing was successfully completed in 2003.

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). Adding wall sections can increase the length of the work area from 42 ft to 102 ft. By swapping the positions of the semi-tractor and the rear wheels, workers can reconfigure the device for placement on the left or the right side of the road. The system was certified as NCHRP Report 350 Test Level 3 and Manual for Assessing Safety Hardware (MASH16) compliant for Test Level-2 and Test Level-3 for use on the National Highway System. 2.7.8 State of the Practice Mobile barriers are used frequently in California, Florida, Oregon, and Washington. 2.7.9 Cost The estimated cost of a mobile barrier can be upwards of $300,000 depending on the vehicle options selected. 2.7.10 Resources and References Arico, M. C., and B. Ravani. Balsi Beam Deployment Support. CA09-0981, AHMCT Research Center, University of California at Davis. October 30, 2008. Bligh, R. P., N. M. Sheikh, W. L. Menges, and R. R. Haug. Portable Concrete Traffic Barrier for Maintenance Operations, FHWA/TX-05/0-4692-1, Texas A&M Transportation Institute, May 2005. Burkett, G., V. Her, and S. A. Velinsky. Development of New Kinds of Mobile Safety Barriers. CA09-0920, AHMCT Research Center, University of California at Davis, February 28, 2009. Gambatese, J. A., and N. Tymvios. Evaluation of a Mobile Work Zone Barrier System. Oregon State University. FHWA-OR-RD-14-05. August 2013. Figure 2.20. Balsi Beam (Credit: Caltrans). Figure 2.21. MBT-1 (Credit: Mobile Barriers LLC).

Work Zone Safety Management Strategies 45 Lohse, C., D. A. Bennett, and S. A. Velinsky. Temporary Barrier Usage in Work Zones. CA07-0915, AHMCT Research Center, University of California at Davis, June 30, 2007. Manual for Assessing Safety Hardware, 2nd ed. AASHTO, Washington, D.C., 2016. [MASH16] Mortazavi, A. Balsi Beam: Technology Transfer and Deployment. CA10-1653, California Center for Innovative Transportation, University of California at Berkeley, July 2010. Portable Positive Protection: A Guide for Short Duration and Short Term Work Zones, American Traffic Safety Services Association (ATSSA), September 2015. Price, G. C. Cost-Benefit Analysis & Justification: Mobile Barriers MBT-1, June 2017. Ravani, B., J. Wong, P. Fyhrie, and R. Bosler. Scientific Evaluation of the ArmorGuard Mobile Barrier System. CA11-1842, AHMCT Research Center, University of California at Davis. June 17, 2011. Ross, H. E., Jr., D. L. Sicking, and R. A. Zimmer. NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features. TRB, National Research Council, Washington, D.C., 1993. Theiss, L., and R. P. Bligh. Worker Safety During Operations with Mobile Attenuators, FHWA/TX-13/0-6707-1, Texas A&M Transportation Institute, May 2013.