Performance Criteria for Retroreflective Pavement Markers (2022) / Chapter Skim
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Pages 104-123
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From page 104... ...
104 Driver Performance Evaluations This chapter describes an analysis of the effectiveness of RPMs using the SHRP 2 naturalistic driving study (NDS) data.
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From page 105... ...
Driver Performance Evaluations 105 5.1.2 Identification of Study Locations for Tangent Sections Presence of RPMs is not a reported variable within the RID. As a result, it was necessary to manually identify potential study locations.
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106 Performance Criteria for Retroreflective Pavement Markers coded for a sample that was sufficient for the analyses. The quality of the RPM beyond when significantly worn could not be determined using only a forward view and, as a result, was not practical to include as a characteristic.
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Driver Performance Evaluations 107 were available. Other curve-specific roadway features were extracted using the SHRP 2 RID or manual video extraction, including the following: • Curve radius and length (ft)
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108 Performance Criteria for Retroreflective Pavement Markers Environmental characteristics were extracted for each time series trace for both tangents and sections. A time stamp indicated time of day, but it was not practical to look up sunrise/sunset times for each trace.
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Driver Performance Evaluations 109 trace. Over half of the traces were reviewed by both data reductionists to ensure coding was consistent.
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110 Performance Criteria for Retroreflective Pavement Markers Different statistical models, such as GLMs, were considered for each response variable (i.e., speed on curves)
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Driver Performance Evaluations 111 Random effects were included in the model. A unique driver ID was used to account for repeated samples from the same driver/vehicle for both tangents and curves.
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112 Performance Criteria for Retroreflective Pavement Markers • RPMs and surface condition • Age and time of day • RPMs, time of day, and age When interactions between variables exist, results for individual variables should be used with caution. A general trend showed the presence of RPMs increased speeds by 1.56 mph.
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From page 113... ...
Driver Performance Evaluations 113 to be noticed by drivers during the day, nor do they provide much additional delineation when headlights are not in use. Consequently, the daytime impact of RPMs might encompass roadway characteristics other than those that could be included in the model, which were consistent among roadways treated with RPMs.
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114 Performance Criteria for Retroreflective Pavement Markers 1.2 mph. As shoulder width increased, the model found that drivers increased their speed as well, although the increase was minor (0.2 mph for every additional foot of shoulder)
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Driver Performance Evaluations 115 response variable. As noted in Table 71, the only relevant predictor variables were length of the test section and presence of RPMs.
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From page 116... ...
116 Performance Criteria for Retroreflective Pavement Markers The model found that the factor that had the most effect on MAD of speed was curve length. As the curve length increased by a factor of 10, for instance, from 100 ft to 1,000 ft, speed deviation was expected to increase by 41.9%.
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Driver Performance Evaluations 117 Table 74. Estimates for tangent lateral position prediction model.
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118 Performance Criteria for Retroreflective Pavement Markers approximation of lateral position in the absence of other significant variables, the average lane position was 17.24 cm to the left of the lane center on the tangent section. As a result, in all cases, vehicles moved closer to the center of the lane during wet/obvious rain and during the nighttime when RPMs were present.
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From page 119... ...
Driver Performance Evaluations 119 older drivers shifted 1.65 cm toward the inside of the curve when RPMs were present relative to when they were not. On average, drivers positioned themselves around 63.85 cm to the left of the center of the lane on curves (intercept)
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120 Performance Criteria for Retroreflective Pavement Markers Table 81. MAD of lateral position model output for curves.
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Driver Performance Evaluations 121 Table 83 shows the percent increase or decrease in mean absolute lateral deviation on curves with RPMs during day or night by age group relative to the deviation on curves without RPMs. The number in parentheses is the parameter estimate used to calculate the percent.
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From page 122... ...
122 Performance Criteria for Retroreflective Pavement Markers In general, RPMs increased speed (1.4 mph) for younger drivers on tangents at night, which is likely due to increased risk-taking by younger drivers.
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From page 123... ...
Driver Performance Evaluations 123 guardrail and RPMs were present, MAD increased by 4% compared to when no guardrail was present for driving on the inside of the curve. For driving on the outside of the curve when RPMs were present, a 50% increase in MAD occurred when guardrail was present compared to when not present.
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