National Academies Press: OpenBook
« Previous: Chapter 5. Study Design
Page 96
Suggested Citation:"Chapter 6. Data Collection." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
×
Page 96
Page 97
Suggested Citation:"Chapter 6. Data Collection." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
×
Page 97
Page 98
Suggested Citation:"Chapter 6. Data Collection." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
×
Page 98
Page 99
Suggested Citation:"Chapter 6. Data Collection." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
×
Page 99
Page 100
Suggested Citation:"Chapter 6. Data Collection." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
×
Page 100
Page 101
Suggested Citation:"Chapter 6. Data Collection." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
×
Page 101
Page 102
Suggested Citation:"Chapter 6. Data Collection." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
×
Page 102
Page 103
Suggested Citation:"Chapter 6. Data Collection." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
×
Page 103
Page 104
Suggested Citation:"Chapter 6. Data Collection." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
×
Page 104
Page 105
Suggested Citation:"Chapter 6. Data Collection." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
×
Page 105
Page 106
Suggested Citation:"Chapter 6. Data Collection." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
×
Page 106
Page 107
Suggested Citation:"Chapter 6. Data Collection." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
×
Page 107
Page 108
Suggested Citation:"Chapter 6. Data Collection." National Academies of Sciences, Engineering, and Medicine. 2021. Application of Crash Modification Factors for Access Management, Volume 2: Research Overview. Washington, DC: The National Academies Press. doi: 10.17226/26162.
×
Page 108

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

84 C H A P T E R 6 Data Collection Introduction The objective of Task 7 was to collect crash, roadway, and traffic characteristic data as defined in the study design. This project leveraged existing datasets as described in chapter 3 to minimize duplication of efforts and maximize the amount of data for analysis in this study. The data were collected in phases to allow for interim analysis, which helped inform the subsequent data collection efforts. After conducting the interim analyses, the project team collected additional data, finalized the datasets, and prepared for the final analysis. This chapter describes the data collection effort, including the existing datasets used in this project, the data collection process, and a summary of the final datasets. Existing Datasets Used Chapter 3 identified existing data sources and indicated the availability and quality of data to support this research. Potential datasets included those used by project team members for safety research either directly or indirectly related to access management, a review of completed safety research projects sponsored by either NCHRP or FHWA, and a literature search using the TRID database. The focus was on datasets prepared in roughly the previous five years. This focus reflects a desire to use current data in future research, as well as difficulties in acquiring and/or adding additional variables to old data as circumstances change over time. The focus of the research is on developing access management CMFs to integrate into the Highway Safety Manual (1st Edition). As such, the natural selection is to use the databases assembled for developing the Highway Safety Manual (1st Edition) SPFs. NCHRP Project 17-62 compiled datasets for urban and suburban arterials, including data for road segments and intersections. These datasets include the original data for estimating SPFs for the Highway Safety Manual (1st Edition) and some access management features. The project team leveraged the existing data from NCHRP Project 17-62 and supplemented these datasets with additional access management variables. Table 58 lists the additional variables that were collected to facilitate the research.

85 Table 58. Additional variables collected. Strategy Substrategy Site Type1 Variables to Collect Manage location, spacing, and design of median openings and crossovers Create directional median opening 4D Segments Type of median opening (full, directional, jug handle) Presence of left-turn lane at median opening Number of median openings in segment Minimum, maximum, and average median spacing in segment Regulate median opening density 4D Segments Regulate median opening spacing 4D Segments Manage location and spacing of unsignalized access Establish spacing for unsignalized access 2U, 3T, 4U, 4D, 5T Segments Minimum, maximum, and average unsignalized access spacing in segment Manage the spacing of signalized and unsignalized access on crossroads in the vicinity of freeway interchanges Establish spacing criteria for interchange ramp terminals 3ST, 3SG, 4ST, 4SG Intersections Spacing from ramp terminal to signalized or unsignalized intersection Establish corner clearance criteria Driveways at signalized and unsignalized intersections 2U, 3T, 4U, 4D, 5T Segments Minimum, maximum, and average spacing for driveways at signalized and unsignalized intersections in segment Manage spacing of traffic signals Establish traffic signal density criteria 2U, 3T, 4U, 4D, 5T Segments Number of traffic signals in segment Minimum, maximum, and average signalized intersection spacing in segment Establish traffic signal spacing criteria 2U, 3T, 4U, 4D, 5T Segments Right-turn treatment Channelize right- turn lane 3ST, 3SG, 4ST, 4SG Intersections Presence of right-turn lane by leg Channelization of right-turn lane by leg 12U = two-lane undivided; 3T = two-lane with TWLTL; 4U = four-lane undivided; 4D = four-lane divided; 5T = four- lane with TWLTL; 3ST = three-legged stop-controlled; 4ST = four-legged stop-controlled; 3SG = three-legged signalized; 4SG = four-legged signalized The data from Project 17-62 includes segments from Ohio and Minnesota and intersections from Ohio and North Carolina. The intersection data from Ohio and North Carolina included sites for all Highway Safety Manual (1st Edition) urban and suburban intersection types: 3ST, 4ST, 3SG, 4SG. The access management strategies considered included distance to ramp terminal and the provision of a channelized right-turn lane. For distance to ramp terminal, only sites with a measured ramp terminal distance were used. The segment data from Ohio and Minnesota included sites for all Highway Safety Manual (1st Edition) urban and suburban segment types: 2U, 3T, 4D, 4U, 5T. The access management strategies considered included median opening spacing, number of median openings and density by type (full, directional, with/without left-turn lanes), spacing of unsignalized access, number and density of unsignalized intersections, spacing of signalized intersections, number and density of signalized intersections, and corner clearance for unsignalized and signalized intersections. Data Collection Process The first step in collecting access management features was to identify the locations of interest in Google Earth. The original data from NCHRP Project 17-62 included intersection data (Ohio and North Carolina) and roadway segment data (Ohio and Minnesota). The original data from NCHRP Project 17-62 came in Excel spreadsheets. Although the data formats vary slightly among the states, the data files had the following essential location identifying variables:  Major route numbers (and minor route numbers and minor road names for intersection data),  County name/codes, and  Major route mileposts (and minor route mileposts for intersection data).

86 The North Carolina intersection data included latitude and longitude coordinates, which allowed the identification of those intersections in Google Earth. Both segment and intersection data files for Ohio and Minnesota did not include coordinate information. Although the search function in Google Earth can work with road names, it does not accept these location identifiers directly. As such, the project team had to develop an alternative method to locate these sites quickly and reliably. Specifically, the project team developed a solution to link the NCHRP 17-62 data and Google Earth using geographic information system (GIS) data. This approach involved a GIS shapefile with milepost markers that the project team obtained from Ohio DOT and Minnesota DOT websites. These milepost markers included coordinate information that allowed the project team to map the exact location of each intersection of interest in Google Earth. The following is a summary of the four-step process to identify the locations of interest in Google Earth and collect the additional access management variables: Step 1: Export Coordinates of Milepost Markers In this step, the project team first imported the GIS shapefile with all milepost markers into ESRI’s ArcMap software and converted coordinates to WGS84 that was compatible with Google Earth. Each milepost marker in GIS also included other location identifiers such as route code, route number, county, and milepost. Figure 24 shows an example screenshot of the markers and related information in ArcMap. The project team then exported these coordinates with all related identifying variables to an external spreadsheet for further processing. Figure 24. Screenshot of milepost markers in GIS. Step 2: Encode Information Exported in Step 1 In this step, the project team used Keyhole Markup Language (KML) codes to create and import milepost markers into Google Earth. For each marker, the project team used the coordinates from GIS for its exact location and attached the location identifiers (i.e., route number, county, and milepost) to each marker’s caption for easy identification. Figure 25 shows a screenshot of Milepost 5 (MP-5) in Franklin County (Cnty_FRA) on State route (SR)- 104 in Ohio. The information for this same milepost marker is highlighted in Figure 24. It is also important

87 to note that in Ohio, mileposts reset at each county line so both milepost and county name are necessary. For Minnesota data, however, the mileposts do not reset back to zero at county line, so only mileposts are necessary. Source: “Stringtown Road.” 39deg52’39.21” N and 83deg01’40.64” W. Google Earth. March 17, 2018. July 3, 2019. Figure 25. Screenshot of a milepost marker in Google Earth. Step 3: Identify Location of Interest in Google Earth Using milepost markers in Google Earth, the project team could identify the exact location of each intersection or the beginning and ending mileposts of each segment from the NCHRP 17-62 data file. Figure 26 shows a screenshot of the Ohio intersection data spreadsheet. By matching major route (MajRoute), County code (CountyCd), and major route milepost (LogRound) with the milepost markers in Google Earth, and using the Google Earth measure tool, the project team measured from the mile markers to locate each intersection. The minor road name (MinRoadName) was used to confirm the location. For example, the highlighted row in Figure 26 shows the information for an intersection on SR-104 at mile 4.98 in Franklin County (also shown in Figure 24 and Figure 25). It is 0.02 miles from SR-104’s mile marker 5 in Franklin County. Figure 26 shows that the minor road is Stringtown Road, and this is confirmed by the road name in Figure 25. Although the Ohio and Minnesota segment data files are not identical to the example here, the principle of the method is still the same.

88 Figure 26. Screenshot of intersection location information from NCHRP 17-62. Step 4: Collect Access Management Features After locating and confirming the intersection or segment of interest, the project team verified the key information such as intersection configuration (i.e., number of legs) and traffic control type (i.e., stop- controlled or signalized), number of lanes, and median presence. The project team then collected the additional access management features. If an intersection or a segment was determined to have unusual configuration (e.g., heavily skewed intersection or very short segment), the data collector flagged for review and potential deletion and proceeded to the next location. The project team used both aerial imagery and street view modes in Google Earth to gather the information. In this process, the project team collected the following variables for intersections:  ML_1_LANES: total number of lanes (through lanes only) on the major route following the approach toward the intersection in increasing milepost direction.  ML_1_RTL_EXCLUSIVE: number of lanes on the major route that are right turn only in increasing milepost direction toward the intersection. Vehicles are not permitted to proceed through the intersection from these lanes.  ML_1_RTL_SHARED: number of shared right turn lanes on the major route that allow vehicles to go through the intersection or turn right in increasing milepost direction toward the intersection.  ML_1_RTL_Channelized: number of lanes on the major route that are channelized right turn lanes in increasing milepost direction toward the intersection. These should be separated lanes that are exclusive right turns. The separation can be raised (curb) or painted.  ML_1_LTL_EXCLUSIVE: number of lanes on the major route that are left turn only in increasing milepost direction toward the intersection. Vehicles are not permitted to proceed through the intersection from these lanes.  ML_1_LTL_SHARED: number of lanes on the major route that allow vehicles to go through the intersection or turn left in increasing milepost direction toward the intersection.  ML_1_LTL_OFFSET: number of lanes on the major route that are offset left turn lanes in increasing milepost direction toward the intersection. These should be lanes that are non-symmetrical and exclusive to a left turn.  ML_2_LANES: total number of lanes (through lanes only) on the major route following the approach toward the intersection in decreasing milepost direction.  ML_2_RTL_EXCLUSIVE: number of lanes on the major route that are right turn only in decreasing milepost direction toward the intersection. Vehicles are not permitted to proceed through the intersection from these lanes.  ML_2_RTL_SHARED: number of shared right turn lanes on the major route that allow vehicles to go through the intersection or turn right in decreasing milepost direction toward the intersection.

89  ML_2_RTL_Channelized: number of lanes on the major route that are channelized right turn lanes in decreasing milepost direction toward the intersection. These should be separated lanes that are exclusive right turns. The separation can be raised (curb) or painted.  ML_2_LTL_EXCLUSIVE: number of lanes on the major route that are left turn only in decreasing milepost direction toward the intersection. Vehicles are not permitted to proceed through the intersection from these lanes.  ML_2_LTL_SHARED: number of lanes on the major route that allow vehicles to go through the intersection or turn left in decreasing milepost direction toward the intersection.  ML_2_LTL_OFFSET: number of lanes on the major route that are offset left turn lanes in decreasing milepost direction toward the intersection. These should be lanes that are non-symmetrical and exclusive to a left turn.  CR_1_LANES: total number of lanes (through lanes only) following the first minor approach toward the intersection. The first minor approach (CR_1) is defined by the leg that is left of ML_1. If it is a three- legged intersection, it does not matter if CR_1 is left or right of ML_1.  CR_1_ONEWAY: indicator for one-way traffic operation of CR_1.  CR_1_RTL_EXCLUSIVE: number of lanes on the first minor approach toward the intersection that are right turn only. Vehicles are not permitted to proceed through the intersection from these lanes.  CR_1_RTL_SHARED: number of shared right turn lanes on the first minor approach toward the intersection that allow vehicles to go through an intersection or turn right.  CR_1_RTL_Channelized: number of lanes on the first minor approach toward the intersection that are channelized right turn lanes. These should be separated lanes that are exclusive right turns. The separation can be raised (curb) or painted.  CR_1_LTL_EXCLUSIVE: number of lanes on the first minor approach toward the intersection that are left turn only. Vehicles are not permitted to proceed through the intersection from these lanes.  CR_1_LTL_SHARED: number of shared right turn lanes on the first minor approach toward the intersection that allow vehicles to go through the intersection or turn left.  CR_1_LTL_OFFSET: number of lanes on the first minor approach toward the intersection that are offset left turn lanes. These should be lanes that are non-symmetrical and exclusive to a left turn.  CR_2_LANES: total number of lanes (through lanes only) following the second minor approach toward the intersection. CR_2 is defined by the leg that is right of ML_1. This is not applicable if it is a three- legged intersection.  CR_2_ONEWAY: indicator for one-way traffic operation of CR_2.  CR_2_RTL_EXCLUSIVE: number of lanes on the second minor approach toward the intersection that are right turn only. Vehicles are not permitted to proceed through the intersection from these lanes.  CR_2_RTL_SHARED: number of shared right turn lanes on the second minor approach toward the intersection that allow vehicles to go through the intersection or turn right.  CR_2_RTL_Channelized: number of lanes on the second minor approach toward the intersection that are channelized right turn lanes. These should be separated lanes that are exclusive right turns. The separation can be raised (curb) or painted.  CR_2_LTL_EXCLUSIVE: number of lanes on the second minor approach toward the intersection that are left turn only. Vehicles are not permitted to proceed through the intersection from these lanes.  CR_2_LTL_SHARED: number of shared right turn lanes on the second minor approach toward the intersection that allow vehicles to go through the intersection or turn left.  CR_2_LTL_OFFSET: number of lanes on the second minor approach toward the intersection that are offset left turn lanes. These should be lanes that are non-symmetrical and exclusive to a left turn.  Distance_to_ramp: the distance in feet is recorded if a ramp is within a half mile (2,640 ft.) of the intersection.

90 For roadway segments, the project team collected the following variables:  No of FULL MO: number of full median openings, only applicable to segments divided by a physical median.  No of 1-direction MO: number of 1-way directional median openings.  No of 2-direction MO: number of 2-way directional median openings.  No of JUG HANDLE MO: number of jug-handle median openings  No of MO w/LTL: number of median openings with a left-turn lane. This includes all types of median openings.  No of 1-direction MO w/LTL: number of 1-direction median openings with a left-turn lane.  No of 2-direction MO w/LTL: number of 2-direction median openings with a left-turn lane.  Max_MO_spacing: maximum spacing between median openings (in feet).  Min_MO_spacing: minimum spacing between median openings (in feet).  No_of_1-way driveways: number of 1-way driveways within the segment on both sides of the road.  No_of_2-way driveways: number of 2-way driveways within the segment on both sides of the road.  No of 3-leg_stop_ ints: number of 3-legged stop-controlled intersections within the segment.  No of 4-leg_stop_ ints: number of 4-legged stop-controlled intersections within the segment.  Max_stop_int_spacing: maximum spacing between stop-controlled intersections (in feet).  Min_stop_int_spacing: minimum spacing between stop-controlled intersections (in feet).  No of 3-leg_signal_int: number of 3-legged signalized intersections within the segment.  No of 4-leg_signal_int: number of 4-legged signalized intersections within the segment.  Max_signal_int_spacing: maximum spacing between signalized intersections (in feet).  Min_signal_int_spacing: minimum spacing between signalized intersections (in feet).  TYPE-1: type of traffic control (i.e., signal or stop-controlled) at intersection number 1 within the segment (count in the increasing milepost direction of the major road).  CC-1-ML_1A: corner clearance (i.e., distance from the street corner of the intersection to the nearest driveway, in feet) on the arriving approach, in the increasing milepost direction of the major road at intersection number 1.  CC-1-ML_1D: corner clearance (i.e., distance from the street corner of the intersection to the nearest driveway, in feet) on the departing approach, in the increasing milepost direction of the major road at intersection number 1.  CC-1_ML_2A: corner clearance (i.e., distance from the street corner of the intersection to the nearest driveway, in feet) on the arriving approach, in the decreasing milepost direction of the major road at intersection number 1.  CC-1_ML_2D: corner clearance (i.e., distance from the street corner of the intersection to the nearest driveway, in feet) on the departing approach, in the decreasing milepost direction of the major road at intersection number 1.  The above five variables (from TYPE-1 to CC-1_ML_2D) were also collected for other intersections within each segment (up to 6). After completing the initial data collection, the project team conducted a review of the data to identify conflicting information. For example, if an intersection was coded as 3-legged but data for CR_2 (the second crossroad) variables were populated, then the project team examined the intersection in Google Earth again to resolve the discrepancy. The project team also corrected facility types as needed based on visual verification in Google Earth. Summary Statistics The project team performed this manual data collection for over 3,500 intersections, both signalized and stop-controlled, and nearly 4,000 segments throughout Ohio, over 240 intersections from North Carolina,

91 and nearly 500 segments from Minnesota. Table 59 to Table 66 provide the data summaries for both intersection and segment data by state. Table 59 and Table 60 provide the number of intersections and sum of multi-vehicle (MV) and single-vehicle (SV) crashes for four site types for Ohio and North Carolina: 3- legged stop-controlled intersections (3ST), 4-legged stop-controlled intersections (4ST), 3-legged signal- controlled intersections (3SG), and 4-legged signal-controlled intersections (4SG). Both MV and SV crashes are categorized into total crashes (KABCO, K-fatal injury, A-incapacitating injury, B-non- capacitating injury, C-possible injury, and O-no injury), injury crashes (KABC), and non-injury crashes (O). The project team categorized crashes this way so that the analyses are consistent with the format of SPFs in the Highway Safety Manual (1st Edition). Note that the data does not include vehicle-pedestrian or vehicle-bicycle crashes. In the Highway Safety Manual (1st Edition), separate models are available for predicting those crash types. Any CMFs developed for access management variables would not be applied to the models for vehicle-pedestrian or vehicle-bicycle crashes. Table 59. Number of intersections and crash totals by intersection type (Ohio). Site Type Number of Sites MV KABCO Crashes MV KABC Crashes MV O Crashes SV KABCO Crashes SV KABC Crashes SV O Crashes 3ST 1,792 3,319 982 2,337 803 253 550 4ST 439 1,325 477 848 208 55 153 3SG 218 2,217 478 1,739 158 42 116 4SG 488 5,630 1,403 4,227 335 90 245 Table 60: Number of intersections and crash totals by intersection type (North Carolina). Site Type Number of Sites MV KABCO Crashes MV KABC Crashes MV O Crashes SV KABCO Crashes SV KABC Crashes SV O Crashes 3ST 52 259 79 180 45 23 22 4ST 36 386 152 234 38 14 24 3SG 19 516 137 379 37 12 25 4SG 102 5,793 1,772 4,021 256 100 156 Table 61 and Table 62 provide descriptive statistics by intersection type for Ohio and North Carolina, respectively. The majority of intersections do not have left-turn, right-turn, or channelized right-turn lanes. None of the signalized sites have right-turn-on-red prohibition or red-light cameras and all have lighting and permitted left-turn phasing. None of the unsignalized sites have lighting. These conditions are consistent with the base conditions in the Highway Safety Manual (1st Edition).

92 Table 61. Descriptive statistics by intersection type (Ohio). Variable 3ST 4ST 3SG 4SG Major Road AADT Min – 270 Max – 32,930 Mean – 8,351 Min – 450 Max – 32,930 Mean – 7,699 Min – 3,050 Max – 24,290 Mean – 13,510 Min – 1,810 Max – 34,960 Mean – 11,495 Minor Road AADT Min – 33 Max – 14,172 Mean – 2,137 Min – 50 Max – 10,730 Mean – 2,045 Min – 72 Max – 14,172 Mean – 3,675 Min – 72 Max – 16,390 Mean – 3,532 Pedestrian Volume n/a n/a Min – 0 Max – 1,700 Mean – 800 Min – 0 Max – 3,200 Mean – 1,352 Approaches with Left-Turn Lanes 0 – 1,631 1 – 141 2 – 19 3 – 1 4 – 0 0 – 374 1 – 15 2 – 39 3 – 4 4 – 7 0 – 159 1 – 41 2 – 18 3 – 0 4 – 0 0 – 371 1 – 26 2 – 59 3 – 12 4 – 20 Approaches with Right-Turn Lanes 0 – 1,730 1 – 50 2 – 12 3 – 0 4 – 0 0 – 407 1 – 22 2 – 10 3 – 0 4 – 0 0 – 180 1 – 34 2 – 4 3 – 0 4 – 0 0 – 436 1 – 40 2 – 8 3 – 3 4 – 1 Lighting Yes – 0 No – 1,792 Yes – 0 No – 439 Yes – 218 No – 0 Yes – 488 No – 0 Left-Turn Phasing n/a n/a Permitted – 218 Protected – 0 Prot.-Perm. – 0 Permitted – 488 Protected – 0 Prot.-Perm. – 0 Approaches with Channelized Right-Turn Lanes 0 – 1,777 1 – 13 2 – 2 3 – 0 4 – 0 0 – 427 1 – 9 2 – 1 3 – 0 4 – 2 0 – 213 1 – 5 2 – 0 3 – 0 4 – 0 0 – 482 1 – 5 2 – 0 3 – 0 4 – 1 Distance to ramp terminal1 Min – 106 Max – 2,482 Mean – 831 Min – 256 Max – 2,326 Mean – 1,137 Min – 739 Max – 2,612 Mean – 1,733 Min – 86 Max – 2,342 Mean – 1,124 Notes: n/a indicates not applicable. 1 indicates no values provided when distance is over 0.5 miles and data is based on: 3ST – 30 sites; 4ST – 12 sites; 3SG – 8 sites; 4SG – 18 sites.

93 Table 62. Descriptive statistics by intersection type (North Carolina). Variable 3ST 4ST 3SG 4SG Major Road AADT Min – 67 Max – 45,733 Mean – 7,682 Min – 335 Max – 29,375 Mean – 8,505 Min – 6,650 Max – 32,208 Mean – 14,848 Min – 3,500 Max – 47,063 Mean – 19,754 Minor Road AADT Min – 18 Max – 9,500 Mean – 1,764 Min – 10 Max – 8,625 Mean – 1,245 Min – 2,200 Max – 13,000 Mean – 6,821 Min – 15 Max – 33,625 Mean – 10,053 Pedestrian Volume n/a n/a n/a n/a Approaches with Left-Turn Lanes 0 – 42 1 – 9 2 – 1 3 – 0 4 – 0 0 – 27 1 – 1 2 – 8 3 – 0 4 –0 0 – 2 1 – 4 2 – 12 3 – 1 4 – 0 0 – 6 1 – 2 2 – 21 3 – 8 4 –65 Approaches with Right-Turn Lanes 0 – 43 1 – 6 2 – 2 3 – 1 4 – 0 0 – 31 1 – 5 2 – 0 3 – 0 4 – 0 0 – 1 1 – 4 2 – 14 3 – 0 4 – 0 0 – 25 1 – 21 2 – 30 3 – 13 4 – 13 Lighting Yes – 22 No – 30 Yes – 18 No – 18 Yes – 9 No – 10 Yes – 77 No – 25 Left-Turn Phasing1 n/a n/a Permitted – 0 Protected – 19 Prot.-Perm. – 0 Permitted – 12 Protected – 52 Prot.-Perm. – 38 Approaches with Channelized Right-Turn Lanes 0 – 49 1 – 3 2 – 0 3 – 0 4 – 0 0 – 36 1 – 0 2 – 0 3 – 0 4 – 0 0 – 17 1 – 1 2 – 1 3 – 0 4 – 0 0 – 78 1 – 12 2 – 9 3 – 1 4 – 2 Distance to ramp terminal2 n/a n/a n/a Min – 185 Max – 1,087 Mean – 667 Notes: n/a indicates not applicable. 1 indicates each intersection is characterized by the highest level of protection between intersection legs. 2 indicates no values provided when distance is over 0.5 miles and data is based on: 3ST – 0 sites; 4ST – 0 sites; 3SG – 0 sites; 4SG – 5 sites. Table 63 and Table 64 provide the number of segments, number of miles, multi-vehicle non-driveway crash count (MV non-driveway), single-vehicle crash count (SV), and multi-vehicle driveway-related crash count (MV driveway-related) by segment types for Ohio and Minnesota: 2-lane undivided (2U), 3-lane with two-way left-turn lane (3T), 4-lane divided (4D), 4-lane undivided (4U), and 5-lane with two-way left-turn lane (5T).

94 Table 63. Number of segments and crash totals by segment type (Ohio). Site Type No. Sites No. Miles MV Non-Driveway Crashes SV Crashes MV Driveway-Related Crashes 2U 337 219 1,077 658 213 3T 113 48 415 75 128 4D 387 218 2,224 799 196 4U 216 97 1,047 163 185 5T 157 91 2,056 204 499 Table 64. Number of segments and crash totals by segment type (Minnesota). Site Type No. Sites No. Miles MV Non- Driveway Crashes SV Crashes MV Driveway- Related Crashes 2U 139 29 199 71 17 3T 47 8 82 14 6 4D 133 24 513 97 14 4U 95 15 164 42 13 5T 28 5 119 14 12 Table 65 and Table 66 provide descriptive statistics by segment type for Ohio and Minnesota, respectively.

95 Table 65. Descriptive statistics by segment type (Ohio). Variable 2U 3T 4D 4U 5T Length (mi.) Min – 0.021 Max – 6.293 Mean – 0.650 Min – 0.037 Max – 3.195 Mean – 0.429 Min – 0.050 Max – 5.250 Mean – 0.564 Min – 0.044 Max – 5.964 Mean – 0.450 Min – 0.057 Max – 3.398 Mean – 0.578 AADT Min – 672 Max – 21,544 Mean – 7,124 Min – 3,067 Max – 21,118 Mean – 11,172 Min – 256 Max – 73,102 Mean – 17,025 Min – 1,658 Max – 38,214 Mean – 15,073 Min – 5,356 Max – 54,298 Mean – 20,217 Proportion of Curb Length with On- Street Parking Min – 0.00 Max – 1.00 Mean – 0.09 Min – 0.00 Max – 1.00 Mean – 0.05 Min – 0.00 Max – 1.00 Mean – 0.02 Min – 0.00 Max – 1.00 Mean – 0.05 Min – 0.00 Max – 1.00 Mean – 0.02 Roadside Fixed Object Density (per mile) Min – 25 Max – 75 Mean – 42 Min – 25 Max – 75 Mean – 48 Min – 25 Max – 75 Mean – 36 Min – 25 Max – 75 Mean – 49 Min – 25 Max – 75 Mean – 45 Median Width (ft.) n/a n/a Min – 10 Max – 100 Mean – 22 n/a n/a Lighting Yes – 105 No – 232 Yes – 71 No – 42 Yes – 177 No – 210 Yes – 146 No – 70 Yes – 101 No – 56 Automated Speed Enforcement Yes – 0 No – 337 Yes – 0 No – 113 Yes – 0 No – 387 Yes – 0 No – 216 Yes – 0 No – 157 Number of Median Openings n/a n/a Min – 0 Max – 36 Mean – 1.81 n/a n/a Number of Unsignalized Intersections Min – 0 Max – 15 Mean – 1.1 Min – 0 Max – 14 Mean – 1.0 Min – 0 Max – 23 Mean – 0.5 Min – 0 Max – 50 Mean – 1.2 Min – 0 Max – 26 Mean – 1.7 Number of Driveways Min – 0 Max – 246 Mean – 22.7 Min – 0 Max – 112 Mean – 18.3 Min – 0 Max – 142 Mean – 6.7 Min – 0 Max – 107 Mean – 16.4 Min – 0 Max – 217 Mean – 23.3 Number of Signalized Intersections Min – 0 Max – 7 Mean – 0.4 Min – 0 Max – 5 Mean – 0.8 Min – 0 Max – 26 Mean – 1.0 Min – 0 Max – 16 Mean – 1.2 Min – 0 Max – 11 Mean – 1.5 Corner Clearance (ft.) Min – 15 Max – 4,900 Mean – 219 Min – 15 Max – 720 Mean – 193 Min – 10 Max – 1,516 Mean – 292 Min – 2 Max – 2,073 Mean – 192 Min – 8 Max – 1,547 Mean – 205 Note: n/a indicates not applicable.

96 Table 66. Descriptive statistics by segment type (Minnesota). Variable 2U 3T 4D 4U 5T Length (mi.) Min – 0.101 Max – 1.054 Mean – 0.206 Min – 0.100 Max – 0.487 Mean – 0.165 Min – 0.101 Max – 0.646 Mean – 0.179 Min – 0.103 Max – 0.524 Mean – 0.162 Min – 0.101 Max – 0.361 Mean – 0.166 AADT Min – 777 Max – 22,932 Mean – 10,019 Min – 3,209 Max – 16,561 Mean – 11,044 Min – 3,529 Max – 52,830 Mean – 20,791 Min – 4,812 Max – 29,316 Mean – 10,399 Min – 6,705 Max – 35,770 Mean – 16,551 Proportion of Curb Length with On- Street Parking Min – 0.00 Max – 0.78 Mean – 0.03 Min – 0.00 Max – 0.80 Mean – 0.03 Min – 0.00 Max – 1.65 Mean – 0.03 Min – 0.00 Max – 0.27 Mean – 0.00 Min – 0.00 Max – 0.00 Mean – 0.00 Roadside Fixed Object Density (per mile) Min – 0 Max – 163 Mean – 57 Min – 0 Max – 100 Mean – 36 Min – 0 Max – 129 Mean – 37 Min – 0 Max – 118 Mean – 45 Min – 0 Max – 130 Mean – 57 Median Width (ft.) n/a n/a Min – 4 Max – 50 Mean – 17 n/a n/a Lighting Yes – 38 No – 101 Yes – 26 No – 21 Yes – 76 No – 57 Yes – 50 No – 45 Yes – 23 No – 5 Automated Speed Enforcement Yes – 0 No – 139 Yes – 0 No – 47 Yes – 0 No – 133 Yes – 0 No – 95 Yes – 0 No – 28 Number of Median Openings n/a n/a Min – 0 Max – 3 Mean – 0.36 n/a n/a Number of Unsignalized Intersections Min – 0 Max – 5 Mean – 1.0 Min – 0 Max – 2 Mean – 0.8 Min – 0 Max – 4 Mean – 0.4 Min – 0 Max – 8 Mean – 0.9 Min – 0 Max – 2 Mean – 0.8 Number of Driveways Min – 0 Max – 22 Mean – 3.9 Min – 0 Max – 18 Mean – 6.5 Min – 0 Max – 9 Mean – 0.8 Min – 0 Max – 25 Mean – 6.5 Min – 0 Max – 19 Mean – 5.8 Number of Signalized Intersections Min – 0 Max – 1 Mean – 0.1 Min – 0 Max – 1 Mean – 0.1 Min – 0 Max – 2 Mean – 0.3 Min – 0 Max – 2 Mean – 0.2 Min – 0 Max – 2 Mean – 0.4 Corner Clearance (ft.) Min – 15 Max – 1,470 Mean – 211 Min – 5 Max – 1,190 Mean – 175 Min – 50 Max – 815 Mean – 253 Min – 10 Max – 615 Mean – 145 Min – 50 Max – 450 Mean – 143 Note: n/a indicates not applicable.

Next: Chapter 7. Analysis Results »
Application of Crash Modification Factors for Access Management, Volume 2: Research Overview Get This Book
×
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

The 1st Edition, in 2010, of the AASHTO Highway Safety Manual revolutionized the transportation engineering practice by providing crash modification factors and functions, along with methods that use safety performance functions for estimating the number of crashes within a corridor, subsequent to implementing safety countermeasures.

The TRB National Cooperative Highway Research Program's pre-publication draft ofNCHRP Research Report 974: Application of Crash Modification Factors for Access Management, Volume 2: Research Overview documents the research process related to access management features.

Supplementary to the report is the pre-publication draft of NCHRP Research Report 974: Application of Crash Modification Factors for Access Management, Volume 1: Practitioner’s Guide and a summary presentation for the two volumes.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!