Performance Criteria for Retroreflective Pavement Markers (2022) / Chapter Skim
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From page 12... ...
12 C H A P T E R 2 2.1 Safety-Related Studies Although RPMs have been researched regularly for decades, genuine safety evaluations of the potential countermeasures are relatively scarce, especially considering that most modern guidelines seem primarily based upon NCHRP Report 518 (Bahar et al.
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Literature Review 13 NCHRP Report 518 summarizes the results of seven noteworthy evaluations of the safety effectiveness of RPMs; those seven studies include the following: • Evaluation of the effect of RPMs on nighttime crashes in Georgia (Wright et al.
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14 Performance Criteria for Retroreflective Pavement Markers a linear one, and it is erroneous to assume that volume will be constant before and after the installation of some treatment. • Time trends -- In addition to traffic volumes, safety is also linked to other socioeconomic factors, such as technology and demographics.
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Table 1. Summary of RPM study information from Bahar et al.
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I = installation period; B = before-period length; A = after-period length. Study Reference and Location Site Type Installation Location Time Period Sample Sizes for Treatment and Comparison Groups Dependent Variable Independent Variables Analyzed Comparison Group Other Notes Estimated Effects Pendleton (1996)
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Literature Review 17 Ultimately, six states were used for the evaluation: Illinois, Missouri, New Jersey, New York, Pennsylvania, and Wisconsin. The data from Illinois, New Jersey, New York, and Pennsylvania pertained to two-lane roadways, while data from Missouri, New York, Pennsylvania, and Wisconsin pertained to four-lane freeways.
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18 Performance Criteria for Retroreflective Pavement Markers In 1986, Agent and Creasey developed crash reduction factors (CRFs) for various delineation treatments on horizontal curves in Kentucky.
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Literature Review 19 the before-and-after period to sites with the treatment. The study found an 11.6% reduction in crashes after installation of RPMs, but this result was not statistically significant.
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20 Performance Criteria for Retroreflective Pavement Markers RPMs and delineators for different crash types and severities as different CMFs. The CMFs reported in Table 5 were developed through a log odds method of meta-analysis; therefore, the CMFs are subject to the limitations of the literature used in the meta-analysis.
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Literature Review 21 highest total of run-off-the-road crashes. Mobile County and ALDOT installed RPMs along the edge line of horizontal curves on the top 10 sites in order to improve delineation and visibility.
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22 Performance Criteria for Retroreflective Pavement Markers Recommendations for the use of RPMs may also be drawn from Bahar et al. 2006 study of general retroreflectivity as part of NCHRP Project 17-28.
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Literature Review 23 when visibility is low and speed up when visibility is high. This finding echoes a study by Molino et al.
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24 Performance Criteria for Retroreflective Pavement Markers presence of different types of guardrails using a driving simulator in Italy. Mean speed and lane position were used as surrogate measures.
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Literature Review 25 general consensus is that RPMs provide safety benefits, though the magnitudes of those effects vary by application and location. 2.2 Application-Related Studies In addition to the in-depth scan of research literature to identify potential safety benefits of RPMs, the research team examined journal articles and reports to determine existing or suggested guidelines for the applications of RPMs.
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26 Performance Criteria for Retroreflective Pavement Markers Use of Raised Pavement Markers, FHWA recommends that RPMs should not be installed for an entire year after the use of a rejuvenating agent on pavement (Grant and Bloomfield 1998)
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Literature Review 27 result in departure crashes (Pennell 1993; Grant and Bloomfield 1998)
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28 Performance Criteria for Retroreflective Pavement Markers 2.2.2.3 Spacing Agencies typically install RPMs at three different spacing lengths dependent on lane configuration, striping, and roadway location. These spacing lengths are 80 ft, 40 ft, and 20 ft.
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Literature Review 29 roadway geometry. The spacing may vary under different roadway conditions and operational requirements.
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30 Performance Criteria for Retroreflective Pavement Markers a simulation study to prove that RPMs may be used effectively in conjunction with chevrons to move vehicles away from centerlines. Persaud, Retting, and Lyon (2004)
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Literature Review 31 State University and the University of Iowa used the SHRP 2 data to investigate driver behavior through curves. One finding indicated in the study was that RPMs (as well as chevrons)
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From page 32... ...
32 Performance Criteria for Retroreflective Pavement Markers influencing driver behavior in ways that should impact safety in a positive manner. However, some of the effects of RPMs on the surrogate safety measures, such as increased speed, may actually be indicative of overdriving, which could reduce safety.
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