Work Zone Speed Management (2015)

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20 chapter two WORK ZONE SPEED LIMITS INTRODUCTION This chapter discusses criteria and policies for setting work zone speed limits, penalties for exceeding the limits, and sev- eral devices and technologies that are intended to reduce work zone speeding by enhancing driver awareness of speed limits. SETTING WORK ZONE SPEED LIMITS Several factors deserve consideration when selecting an appro- priate work zone speed limit. Although most U.S. state DOTs have policy guidance on speed limit selection, it can be difficult to create guidelines that are responsive to all project-specific situations. The 2009 MUTCD includes several recommenda- tions that form the basis of most state guidelines (FHWA 2009): • Reduced speed limits should be used only in the specific por- tion of the Temporary Traffic Control (TTC) zone where conditions or restrictive features are present. However, fre- quent changes in the speed limit should be avoided. 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. • A reduction of more than 10 mph in the speed limit should be used only when required by restrictive features in the TTC zone. Where restrictive features justify a speed reduction of more than 10 mph, additional driver notification should be provided. The speed limit should be stepped down in advance of the location requiring the lowest speed, and additional TTC warning devices should be used. • 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. The MUTCD section on Worker Safety Considerations offers a counterpoint: Reducing the speed of vehicular traffic, mainly through regu- latory speed zoning, funneling, lane reduction, or the use of uniformed law enforcement officers or flaggers, should be con- sidered [to improve worker safety]. Imposing a work zone speed limit that drivers perceive to be unreasonably low has been shown to increase speed variation: conservative drivers tend to observe the work zone limit, whereas aggressive drivers may attempt to operate speeds closer to the ordinary limit (without road work). The MUTCD frames the issue as follows: Research has demonstrated that large reductions in the speed limit, such as a 30 mph reduction, 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. More emphatic advice is offered in a 1989 work zone design standard published by MOPU, Spain’s Ministry of Public Works & Urbanism: The most frequent issue is that as the result of routine, laziness, or fear of liability, abnormally low values are set. The attempt to limit speed with signs alone to a value that is not realistic and easily understood by the user not only fails to achieve the intended effect; the limit will be ignored or perceived as a speed trap, causing proper traffic control to be disregarded and reduc- ing its general credibility. The MUTCD and MOPU advice is supported by a late 1990s study that examined the relationships between work zone speed limits and crash rates (Migletz et al. 1999). As shown in Figure 6a and b, the study found that in work zones where the speed limit was not reduced there was an aver- age decrease of 8.2 km/h (5.1 mph) in mean speed and a reduction of 7.2 km/h (4.5 mph) in 85th percentile speed. Compliance with work zone speed limits was generally most effective when the work zone speed limit was not reduced, and compliance decreased where the speed limit was reduced by more than 10 mph. Conversely, when the work zone limit was set 20 mph below the ordinary limit, the mean reduction in actual speeds was only 13.6 mph and the 85th percentile speed went down by just 11.8 mph. Speed variance, a potentially useful surrogate measure for safety, had an important relationship with the speed limit reduction in the Migletz study. The study’s authors asserted that the safest work zones are those with the smallest increase in the upstream-to-work-zone speed variance, and found that the speed limit variance was minimized for a speed limit reduction of 10 mph as shown in Figure 7. These results were developed into a work zone speed limit setting procedure in NCHRP Projects 3-41 and 3-41(2), which have influenced state practices and the MUTCD. Migletz et al. noted: None of the differences between the percentage increases in speed variance . . . were statistically significant. Although disappointing, this finding reflects the diversity of conditions inherent in work zones. Given motorist responses that are so highly variable, it is unlikely that statistically significant differences can be found. Despite the lack of statistical significance, rational policies for setting work zone speed limits must be developed. It was con-

21 limits of 70 mph found a reduction in speed variance when the work zones were posted at 50 or 60 mph instead of 70 mph (Hou et al. 2011). When the Kansas maintenance work zones operated under a 70 mph work zone speed limit, only 51% of the traffic complied with the limit; when the limit was reduced to 60 mph the compliance rate was 74%, and under a 50 mph limit the compliance rate reached almost 90%. Among the agencies that responded to a survey conducted for this synthesis report, 64% reported that they have a formal policy or guideline for determining when to reduce speed lim- its in work zones (Table 3). In most cases, these documents also establish an administrative process for approving reduc- tions that is specific to the agency’s organizational hierarchy. In general, the original posted speed limit and road type are important factors, as are the presence of workers, their prox- imity to traffic, and the duration or physical length of the work zone (Thomson et al. 2014). The type of separation between workers and traffic (e.g., drums vs. concrete barrier) is also sidered reasonable to use the speed variance results . . . as a basis for policy [because] accident analysis provided similar findings and . . . engineering judgment suggested that these findings were reasonable. Two more recent study results differ from MUTCD/Migletz findings and suggest more complex relationships between work zone speed limits, speed variation, and compliance rates. A study of speed profiles along 17 freeway work zones in Penn- sylvania and Texas found that “speed deviations were lower in work zones with a posted speed reduction of 16 or 24 km/h [10 or 15 mph] than in work zones with no speed reduc- tion” and concluded that “at least some magnitude of speed reduction is recommended if lowering speed deviation is a design objective” (Porter and Mason 2008). In addition to the work zone speed limit, the upstream traffic speeds, work zone geometry, and type of work zone delineation (e.g., concrete barrier vs. drums) were found to influence the speed variance. Similarly, a study of three short-term work zones on rural Kansas freeways that had ordinary (nonconstruction) speed FIGURE 6 Mean and 85th percentile speed reductions from upstream to work zone locations: (a) mph, (b) km/h (Migletz et al. 1999). 5.1 7.2 7.8 13.6 12.7 20.7 4.5 5.5 7.0 11.8 10.0 18.0 0.0 5.0 10.0 15.0 20.0 25.0 0 10 15 20 25 30 Sp ee d R ed uc ti on (m ph ) Speed Limit Reduction (mph) Mean Speed Reduction (mph) 85th Percentile Speed Reduction (mph) 8.2 11.6 12.6 21.9 20.4 33.3 7.2 8.9 11.3 19.0 16.1 29.0 0 5 10 15 20 25 30 35 0 16 24 32 40 48 Sp ee d Re du cti on (k m /h ) Speed Limit Reduction (km/h) Mean Speed Reduction (km/h) 85th Percentile Speed Reduction (km/h) (a) (b)

22 limit; the criteria include narrow lane width, narrow shoulder width, lateral shifting of the lanes, work operations close to an open lane, and traffic operating on shoulders, temporary pavement, or gravel. A simplified flowchart for setting work zone speed limits published by the Roadway Safety Consor- tium in 2010 is reproduced as Figure 8. The exact criteria used in setting work zone speed limits (and the extent to which the limits can be modified based on engineering judgment) vary jurisdictionally. Table 5, produced frequently mentioned. Statutory work zone speed limits are also a consideration, particularly in states that have lower speed limits when workers are present. In most cases, the technical content of the state guidelines is based on a combination of the MUTCD recommendations, results of the Migletz study, local experience, and factors such as those listed in Table 4. For example, a Wisconsin DOT guideline (WisDOT 2013) provides criteria that could result in a reduction of 5 or 10 mph from the ordinary speed 62.1 34.1 86.7 82.6 92.6 80.6 0 10 20 30 40 50 60 70 80 90 100 0 10 15 20 25 30 Pe rc en ag e In cr ea se s ( % ) Speed Limit Reduction (mph) 62.1 34.1 86.7 82.6 92.6 80.6 0 10 20 30 40 50 60 70 80 90 100 0 16 24 32 40 48 Pe rc en ta ge In cr ea se s ( % ) Speed Limit Reduction (km/h) (a) (b) FIGURE 7 Percentage increase in speed variance from upstream to work zone locations: (a) mph, (b) km/h (Migletz et al. 1999). Agency Policies on Work Zone Speed Limit Setting Yes No No Response Total Formal Policy or Guideline Exists 64% 32% 4% 100% Policy Implemented Uniformly 52% 8% 40% 100% Policy Posted on Organization’s Website 34% 26% 40% 100% TABLE 3 AGENCY POLICIES ON SETTING WORK ZONE SPEED LIMITS

23 • Traffic mix and vulnerable road users • Crash history • Road shoulder width and pavement quality • Road delineation • Road and lane widths • Abutting land development • Type of intersections and traffic control • Traffic volume and traffic flow • Types of vehicles allowed • Access • Free-flow speed • Ability to overtake [pass] safely (within sight distance) at posted speed Source: Howard et al. (2008). TABLE 4 GENERAL FACTORS TO CONSIDER WHEN SETTING SPEED LIMITS FIGURE 8 Simplified flowchart for setting work zone speed limits (Roadway Safety Consortium 2010). for the Conference of European Directors of Roads (CEDR), summarizes the work zone speed limit setting criteria men- tioned in official guidelines from 17 countries (including four U.S. states and the U.S. MUTCD). As of 2014, CEDR’s ASAP project was attempting to build on the Migletz research to develop unified criteria for use throughout the European Union (Thomson 2014). As of this writing, the January 2014 edition of Book 7 of the Ontario Traffic Manual (MTO 2014) provides one of the most recently updated sets of guidelines for determining when to reduce speed limits in construction zones: The travelled way through a work zone should be designed for a speed that is equal to or as close as possible to the design speed of the approaches to the work zone. If a speed limit reduction is deemed necessary, road authorities have the option of using advisory signs or reducing the regulatory speed limit, either tem- porarily or continuously through a construction zone. [Table 6] provides examples of the appropriate uses of each method. Both regulatory and advisory speed limit signs can be used on different portions of the same contract for severe work zone conditions. The road and police authorities should discuss logistics of enforcement and speed control. Regulatory and advisory speed reductions should not be more than 20 km/h (10 mph) below the normal posted speed. Speed limit reductions that are up to 20 km/h have been shown to be the most effective for keeping traffic in compliance, and increasing public and worker safety and mobility. Both advisory and regulatory speed reductions must move with the active operation and there must be visible signs of work activity. When reduced speed limit signs are used for worker safety, the signs must be covered or removed when not required. Speed reductions are more likely to be obeyed by motorists if they are perceived as necessary. If there is a good reason for reducing speed which may not be readily apparent to motor- ists, then the reason for the speed reduction should be provided

24 Method Examples Where Speed Limit Reductions May Be Used Advisory speed limits Used whenever an unexpected change in geometrics is caused by the work activity ▪ Bumps ▪ Low shoulders ▪ Drop-offs ▪ Limited but not substandard sight lines or stopping sight distance ▪ Limited but not substandard horizontal or vertical alignment ▪ Gravel surfaces (length less than 500 m) ▪ Temporary lane closures ▪ Milled surfaces Regulatory Speed Limits Used for temporary worker safety Only to be used when workers present. Workers on a freeway within 3 m (10 ft) of a travelled lane open to traffic where no barrier is used. Regulatory 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 3.5 m (12 ft) on freeways or less than 3.0 m (10 ft) on non-freeways ▪ Shoulder width or offset to barriers less than 0.5 m (1½ ft), one or both sides ▪ Sudden lane narrowing ▪ Substandard sight lines or stopping sight distance ▪ Multiple lane shifts, detours or transition designed at less than the normal posted speed limit or those with no illumination ▪ Substandard horizontal or vertical alignment ▪ Gravel surfaces [length greater than 500 m (¼ mile)] ▪ Multiple lane shifts with overlapping/confusing pavement markings ▪ Partial lane shifts onto a surface texture different from the main roadway. Source: Ministry of Transportation–Ontario (2014). TABLE 6 APPROPRIATE USE OF ADVISORY OR REGULATORY SIGN LIMITS FROM ONTARIO TRAFFIC MANUAL BOOK 7 (TEMPORARY CONDITIONS) TABLE 5 INTERNATIONAL SUMMARY OF PARAMETERS USED TO ASSIGN SPEED LIMITS IN WORK ZONES Original Posted Speed Road Type Lane Width Duration or Length of Construc- tion Workers Present Proximity of Workers to Traffic Impact on Traffic Change- overs and Cross- overs Change in Road Surface Properties Australia New South Wales X X X Queensland X X X X Austria X X X X X Belgium X X X X X Canada Quebec X X X Czech Republic X Denmark X X X X X France X X X X X Germany X X X Ireland X X X X X Italy X X X Luxembourg X X X X Netherlands X X X X X Norway X X X X X X X X Sweden X X X X X Switzerland X X X United Kingdom X X X X X United States MUTCD X X X X Michigan X X X X Minnesota X X New York X X Washington X X X Source: Thomson et al. (2014).

25 The use of advance warning signs such as those shown in Figure 9 is generally considered a most effective practice to provide drivers with additional notice, particularly if the reduction is 10 mph or more. “The addition of advisory speed panels to work zone warning signs may also help in convey- ing to drivers appropriate speeds through specific portions of the project” (Bryden and Mace 2002). Interviews conducted for this project indicate that reinforcing the speed reduction message by placing the speed limit and advance speed reduc- tion signs on both the left and right sides of the road appears to be an increasingly common practice, especially on multi- lane divided highways. INCREASED FINES FOR WORK ZONE SPEEDING According to the Governors Highway Safety Association (GHSA 2014) nearly all U.S. states have increased penalties for speeding or other violations in work zones. The higher penalties are implemented in several ways: • In 33 states and the District of Columbia the fine for work zone speeding is twice the amount for nonwork zone speeding. • In some cases the penalty is a higher fixed amount or range. • In some cases the penalty depends on whether it is a first or subsequent offence. In spite of the relatively widespread implementation of increased penalties, the evidence from field studies indicates that higher penalties have relatively little effect on compli- ance with the work zone speed limit. through advance signage, repeated as necessary. Regulatory speed limit signs shall only be installed when approved by the road authority. Once approved the appropriate police authority must be notified of the regulatory speed change prior to installa- tion. Otherwise, only advisory signs should be used and all exist- ing regulatory speed limit signs within the limits of the speed reduction must be covered or removed for the duration of the construction project. A regulatory speed reduction should be implemented for a minimum road length of 300 m (0.2 miles) or more, even if the work zone is less than 300 m. Speed reductions can be imple- mented in stages. On a divided highway, the road authority may permit different speed limits for each direction of travel. In the case of an express/collector freeway, the speed limit may be low- ered on one roadway, but not on another. There are some philosophical and policy differences about appropriate work zone speed limits. For example, as with Ontario, VDOT prefers to design work zones so as to maintain normal speed limits where possible, but will reduce the speed limit by 10 mph if conditions warrant (D. Rush, VDOT, per- sonal communication, 2014). Pennsylvania DOT (PennDOT) also tries to maintain normal speed limits on freeways, but only if workers are separated from traffic by a barrier. If workers are near live freeway lanes, PennDOT reduces the speed limit based on engineering judgment and experience; agency policy allows a 10 mph reduction without a formal study; however, a 15 mph reduction requires study and doc- umentation (M. Briggs, PennDOT, personal communica- tion, 2014). Although many other U.S. jurisdictions follow speed limit setting procedures that take site conditions and prior experience into consideration, in some cases statutory work zone speed limit provisions limit the discretion of the highway agency or project engineer. A Canadian work zone speed management guide suggests a pragmatic approach: “to assure a high level of compliance, speed limits have to be set at levels that are largely self-enforcing, or at the lowest speed the police are able to enforce” (Harmelink and Edwards 2005). Although the MUTCD discourages setting speed limits more than 10 mph lower than the ordinary speed limit, there are some situations where the nature of the work, the close proximity of workers to live traffic, statutory requirements, or political considerations require a greater reduction. In these instances stepped reduction in increments of 5 mph or 10 mph is generally considered a most effective practice. For example, Virginia has occasionally applied 20 mph reductions (stepped down in 10 mph increments) for bridge deck closures with severe width constraints (D. Rush, VDOT, personal com- munication, 2014). As of 2014, Oregon DOT occasionally approves 35 mph work zone speed limits in situations such as night paving on low-volume freeways; a mandatory limit can be approved if at least two law enforcement officers will be present at the site (a stationary officer at the work zone approach to slow traffic and identify violators, and a mobile officer to intercept violators), otherwise the 35 mph limit is advisory. In these situations Oregon typically steps down the speed in 15 mph increments (65–50–35) (R. Pappe, personal communication, 2014). FIGURE 9 MUTCD W3-5 sign.

26 data the report suggested that double-fine zones may help in reducing crash rates. A study published in 2000 examined the short-term effect of a double-fine law that was implemented in Texas on Janu- ary 1, 1998 (Ullman et al. 2000). Field studies of traffic speeds in several work zones were conducted before and after the implementation of the law. In addition, traffic citation infor- mation was collected for these work zones. Analyses sug- gested that the speeds before and 4 to 6 months after the law came into effect were essentially unchanged. Similarly, cita- tion frequency and fines levied were not significantly higher than they were before the law became effective. A 2002 study evaluated the effectiveness of double fines as a speed control measure in safety corridors in Oregon (Jones et al. 2002). The research was based on a telephone survey of 651 adult drivers in Oregon about their decision to speed in a variety of conditions. Survey analysis was used to infer indirectly the effectiveness of double fines on the driver’s judgment. Most people were aware of double fines in work zones. Jones et al. concluded that effectiveness of double fines is weak, inconsistent, and generally not very conclusive. However, there are indications of a beneficial effect as a result of double fines. The study found that aware- ness of double fines elevates the perception of the risk of traffic fines, traffic citations, and higher insurance costs in school zones and to a lesser extent in work zones. In many states increased penalties are applicable only when workers are present and/or if suitable signs notifying drivers of increased fines are posted. Twenty-four states and the District of Columbia require workers to be present in the work zones as a condition for imposing the higher penalty. In 40 states and the District of Columbia highway agencies are required to install signs notifying drivers of the higher fines as they approach work zones (GHSA 2014). State-specific statutory provisions and case law affect the enforceability of increased fines for work zone speeding. For example, in Virginia work zone speeding fines can be increased to $500, but signs notifying drivers of the increased penalty must be installed and accompanied by flashing lights indicating that workers are present. Contractors are also required to maintain a log of the times when the lights were activated and deacti- vated. VDOT officials report that many contractors view the light activation and recordkeeping as burdensome, result- ing in limited use of the enhanced fines provision (D. Rush, VDOT, personal communication, 2014). In Wisconsin, proj- ect managers are instructed that the courts might not enforce the state’s double-fines law if an end road work sign was not in place when the violation occurred (Shaw et al. 2014). A 1997 report to the California Legislature reviewed the safety effectiveness of double-fine legislation (Khorashadi 1997). Crash and enforcement data for three pilot projects in California were used. Based on analysis of one year’s