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From page 112... ... 100 4. Chapter 4 Data Collection and Preparation This chapter describes the content of the data collected, and the steps involved in preparing a retroreflectivity-safety database to analyze the relationship between retroreflectivity and crashes. Read the entire page →
From page 113... ... 101 Several of the reports also contain data collected and analysed strictly on laboratories. Given the need for producing results that have direct applicability to today's practices, analysis of NTPEP data was limited to field measurements only. Read the entire page →
From page 114... ... 102 An excerpt from the older California system is shown in Table 33 (data show striping data for District 1, Lake County, Route 20) , which contains: • DIST: District number; • FPH: Type of maintenance work, where M1 is striping; • CORTE: County and route information; • WRK-DTE: Date of work; • FRM PM: Starting milepost; • TO PM: Ending milepost; and • CLASS: Material type code. Read the entire page →
From page 115... ... 103 4.1.3. Capital Pavement Projects Marking and marker material installation data, conducted under contract and not done by the Caltrans, were not available for this study. Read the entire page →
From page 116... ... 104 Table 34. Roadway inventory, traffic volume, and crash variables Category Variable Roadway inventory Location (district, county, route, milepost) Read the entire page →
From page 117... ... 105 Table 35. California climate regions County Name Climate Region County Name Climate Region Alameda Marine Orange Hot-Dry Alpine Cold Placer Hot-Dry Amador Mixed-Dry Plumas Cold Butte Hot-Dry Riverside Hot-Dry Calaveras Mixed-Dry Sacramento Hot-Dry CoIusa Hot-Dry Santa Barbara Marine Contra Costa Hot-Dry San Bernardino Hot-Dry Del Norte Marine San Benito Marine El Dorado Mixed-Dry Santa Clara Marine Fresno Hot-Dry Santa Cruz Marine Glenn Hot-Dry San Diego Hot-Dry Humboldt Marine San Francisco Marine Imperial Hot-Dry Shasta Hot-Dry Inyo Mixed-Dry Sierra Cold Kern Hot-Dry Siskiyou Cold Kings Hot-Dry San Joaquin Hot-Dry Lake Mixed-Dry San Luis Obispo Marine Lassen Cold San Mateo Marine Los Angeles Hot-Dry Solano Hot-Dry Madera Hot-Dry Sonoma Marine Marin Marine Stanislaus Hot-Dry Mariposa Mixed-Dry Sutter Hot-Dry Mendocino Marine Tehama Hot-Dry Merced Hot-Dry Trinity Mixed-Dry Modoc Cold Tulare Hot-Dry Mono Cold Tuolumne Mixed-Dry Monterey Marine Ventura Marine Napa Marine Yolo Hot-Dry Nevada Cold Yuba Hot-Dry 4.1.6. Read the entire page →
From page 118... ... 106 In order to apply the appropriate retroreflectivity models, counties in cold regions were classified into low-medium and heavy snowfall counties. Snowfalls over all the weather stations within each county was averaged for each year to get the average value of annual snowfall. Read the entire page →
From page 119... ... 107 The data were subjected to additional quality control processes, which were: 1. Are the data fields complete (are there any missing data elements) Read the entire page →
From page 120... ... 108 4.2.2.2. NTPEP Retroreflectivity Database Structure for Markings The column headings of the NTPEP retroreflectivity database is shown in Table 36. Read the entire page →
From page 121... ... 109 A visual inspection of the retroreflectivity database was conducted to identify outlier values. Outliers refer to those values that for one reason or another are clearly in error. Read the entire page →
From page 122... ... 110 4.2.2.4. NTPEP Retroreflectivity Database Structure for Markers The steps for building the marker retroreflectivity database are identical to the steps described for markings (Section 4.2.2.1) Read the entire page →
From page 123... ... 111 4.2.3. Database Linking In order to build the retroreflectivity-safety database, the different data sources (Table 32) Read the entire page →
From page 124... ... 112 NCDC County Names HSIS County Codes Caltrans Maintenance County Codes Caltrans Resurfacing County Codes Nevada 29 17 NEV Orange 30 55 ORA Placer 31 19 PLA Plumas 32 9 PLU Riverside 33 56 RIV Sacramento 34 24 SAC Santa Barbara 35 51 SB San Bernardino 36 54 SBD San Benito 37 43 SBT Santa Clara 38 37 SCL Santa Cruz 39 36 SCR San Diego 40 57 SD San Francisco 41 34 SF Shasta 42 6 SHA Sierra 43 13 SIE Siskiyou 44 2 SIS San Joaquin 45 29 SJ San Luis Obispo 46 49 SLO San Mateo 47 35 SM Solano 48 23 SOL Sonoma 49 20 SON Stanislaus 50 38 STA Sutter 51 18 SUT Tehama 52 8 THE Trinity 53 5 TRI Tulare 54 46 TUL Tuolumne 55 32 TUO Ventura 56 52 VEN Yolo 57 22 YOL Yuba 58 16 YUB 4.2.4. Database Manipulation The structure of the data needed for safety analysis is different than the structure of the source data. Read the entire page →
From page 125... ... 113 For example, consider a dataset in terms only of marker installation date. Formatting the marker age in month time windows produces an additional 12 columns. Read the entire page →
From page 126... ... 114 Table 42. Detailed illustration of 12 marker luminance columns "Segment" "Year" MRL1 MRL2 MRL3 MRL4 MRL5 MRL6 MRL7 MRL8 MRL9 MRL10 MRL11 MRL12 Sinclair Rd 1998 5.53 4.67 3.81 2.96 2.10 1.24 0.39 0.36 0.33 0.30 0.27 0.24 Sinclair Rd 1999 0.21 0.19 0.17 0.16 0.14 0.12 0.11 0.09 0.06 0.04 0.02 0.00 Sinclair Rd 2000 5.53 4.67 3.81 2.96 2.10 1.24 0.39 0.36 0.33 0.30 0.27 0.24 Sinclair Rd 2000 0.22 0.21 0.19 0.18 0.17 0.15 0.14 0.12 0.11 0.10 0.08 0.07 Main St 1999 0.33 0.30 0.27 0.24 5.53 4.67 3.81 2.96 2.10 1.24 0.39 0.36 Hwy 7 2000 0.39 0.36 0.33 0.30 0.27 0.24 5.53 4.67 3.81 2.96 2.10 1.24 … 1998 0.33 0.30 0.27 0.24 5.53 4.67 3.81 2.96 2.10 1.24 0.39 0.36 … 1997 2.10 1.24 0.39 0.36 0.33 0.30 0.27 0.24 5.53 4.67 3.81 2.96 … 1995 0.33 0.30 0.27 0.24 5.53 4.67 3.81 2.96 2.10 1.24 0.39 0.36 … 1995 0.33 0.30 0.27 0.24 5.53 4.67 3.81 2.96 2.10 1.24 0.39 0.36 Marker Coefficient of Luminous Intensity (cd/foot-candle) Read the entire page →
From page 127... ... 115 Table 43. Retroreflectivity-safety database format and column headings. Read the entire page →
From page 128... ... 116 4.3. Summary of the Retroreflectivity-Safety Database The retroreflectivity-safety database links the following information: • Roadway inventory and traffic volume information as homogenous segments for all California state roads by road type: o 2-lane highways o Multilane highways o Multilane freeways • The number of non-daylight crashes recorded for each homogeneous segment per month by severity: o Fatal + nonfatal injury crashes o Property damage only crashes • The climate region for each county region in California as: o Cold o Hot-dry o Marine o Mixed-dry • The yearly snowfall for cold region counties in California as: o heavy o low to medium • The age of the pavement markings installed by Caltrans maintenance in terms of months. Read the entire page →

From page 112...

... 100 4. Chapter 4 Data Collection and Preparation This chapter describes the content of the data collected, and the steps involved in preparing a retroreflectivity-safety database to analyze the relationship between retroreflectivity and crashes.