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From page 168... ... 168 Appendix A: Literature Review Introduction This appendix presents the literature review for NCHRP Project 17-87, "Enhancing Pedestrian Volume Estimation and Developing HCM Pedestrian Methodologies for Safe and Sustainable Communities," summarizing information relevant to the project objectives from over 300 reviewed documents. Because members of the project team have performed literature reviews for other related projects in the recent past, the information obtained from the following reviews was used as a starting point for this review:  NCHRP Project 17-84, "Pedestrian and Bicycle Safety Performance Functions for the Highway Safety Manual";  NCHRP Project 07-19, "Methods and Technologies for Collecting Pedestrian and Bicycle Volume Data";  NCHRP Project 07-17, "Pedestrian and Bicycle Transportation Along Existing Roads";  NCHRP Project 17-73, "Systemic Pedestrian Safety Analysis";  NCHRP Project 15-63, "Guidance to Improve Pedestrian and Bicycle Safety at Intersections";  NCHRP Project 03-120, "Assessing Interactions Between Access Management Treatments and Multimodal Users";  NCHRP Project 07-25, "Guide for Pedestrian and Bicycle Safety at Alternative Intersections and Interchanges (A.I.I.) Read the entire page →
From page 169... ... 169 Techniques for Efficient and Accurate Estimation of Pedestrian Volume and Exposure Methods to Collect Pedestrian Volume Data Counting pedestrian volumes can be challenging because pedestrians travel without restrictions and often in groups. Hence, automatic detection of pedestrians can be difficult, especially if multiple people travel through the sensor simultaneously. Read the entire page →
From page 170... ... 170 Table A1. Methods for Counting Pedestrians. Read the entire page →
From page 171... ... 171 Counting Method Advantages Disadvantages  Can capture directional counts and potentially distinguish bicycles from pedestrians On shared-use facilities, more than one sensor type may be required to distinguish between pedestrians and bicycles -- for example, a passive infrared sensor will detect all path users, while infrared loops can be used to detect only bicycles, with the pedestrian count being the difference in the two counts (Ryus et al. Read the entire page →
From page 172... ... 172  Outsourcing labor by recruiting volunteers from universities or community groups or engaging different stakeholders (Lindsey et al. Read the entire page →
From page 173... ... 173 pedestrian counts: for example, street block face or midblock count data have been used to model pedestrian volumes in New York (Pushkarev and Zupan 1972) , Milwaukee (Benham and Patel 1977) Read the entire page →
From page 174... ... 174 Table A3. Pedestrian Crash Risk Factors. Read the entire page →
From page 175... ... 175 Studies Categories Risk Factors Impact on Frequency or Severity Poch and Mannering 1996, Schneider et al. 2004, Martin 2006, Loukaitou et al. Read the entire page →
From page 176... ... 176 Studies Categories Risk Factors Impact on Frequency or Severity Loukaitou et al. Read the entire page →
From page 177... ... 177 distribution curves at the 15th percentile, whose value was 3.5 ft/s irrespective of age and 3.0 ft/s if elderly pedestrians were considered (LaPlante 2004) Read the entire page →
From page 178... ... 178 speeds. Alsaleh et al. Read the entire page →
From page 179... ... 179 Table A5. Summary of Speed–Density Studies. Read the entire page →
From page 180... ... 180 Study Location Flow Direction Regimes Speed–Density Equation(s) Kotkar et al. Read the entire page →
From page 181... ... 181  Physical infrastructure – Sidewalk presence – Sidewalk width – Sidewalk continuity – Slope – Bus shelters – Parking – Crosswalk presence – Pedestrian signal – Median island  Road Safety – Vehicular volume – Traffic noise – Traffic fumes – Pedestrian flow rate – Waiting time – Crossing distance  Aesthetics – Sidewalk cleanliness – Sidewalk surface quality and evenness – Obstructions (trash cans, light poles, sign posts, etc.) – Trees and other greenery  Access and Facilities – Disabled pedestrian access – Land use mix  Security – Street lighting – Cameras – Police patrols Many studies have found that pedestrians highly value attributes such as road width, vehicle speed and volumes, connectivity, and lighting conditions that directly impact safety, compared to attributes that are related to comfort or convenience (Araujo et al. Read the entire page →
From page 182... ... 182 Table A6. Summary of Studies on Pedestrian Satisfaction. Read the entire page →
From page 183... ... 183 Study Facility Factors Method Location Key Findings Sahani et al. 2017 Crosswalks Number of lanes crossed, 85th percentile vehicle speed, delay, number of left-turning vehicles, number of permissible right-turning vehicles, number of through vehicles, number of left/right/through nonmotorized vehicles Qualitative data collected using a perception survey, SOM in ANN clustering approach was used to define ranges of PLOS scores for six categories Eight midsize cities in India Total pedestrian delay increases linearly with increase in waiting time delay. Read the entire page →
From page 184... ... 184 Study Facility Factors Method Location Key Findings Hong and Park 2017 Sidewalks Trip attributes (trip frequency, time of day) , trip purpose, sidewalk environment (crosswalk, slope, fence, bus stop, subway stop) Read the entire page →
From page 185... ... 185 Study Facility Factors Method Location Key Findings Zhao et al. 2015 Sidewalks Pedestrian flow rate, bicycle volume, electric bike volume, vehicle volume in the inside lane, sidewalk width, frequency of barriers on sidewalks, sidewalk environment Video observation and intercept survey, followed by modeling using fuzzy neural networks Beijing, China When pedestrian flow rates were low, road facility conditions and environmental factors affected ped LOS, however the impact of these factors weakened as the pedestrian flow rate increased to high-density conditions. Read the entire page →
From page 186... ... 186 Study Facility Factors Method Location Key Findings Martinez and Barros 2014 Walkability Walking impedances (sidewalk quality, presence of barriers, street lighting, parking) ; Topoceptive awareness (land use diversity, presence of open spaces, presence of walls or windows, building height, presence of trees, block length, land use, road hierarchy) Read the entire page →
From page 187... ... 187 Table A7. List of Commonly Used Pedestrian Countermeasures. Read the entire page →
From page 188... ... 188 Table A8. Factors Affecting Pedestrian Safety at Intersections. Read the entire page →
From page 189... ... 189 Table A9. Key Factors Impacting Pedestrian Safety at Crosswalks. Read the entire page →
From page 190... ... 190 Factors Studies Key Findings Median refuge Bowman et al. 1994, Bacquie et al. Read the entire page →
From page 191... ... 191 Table A10. Summary of Countermeasure CMFs. Read the entire page →
From page 192... ... 192 driveway turning speeds and improve sight distance, installing roundabouts, and installing driveways with the appropriate return radii, throat width, and throat length for the type of traffic to be served showed trends which were qualitative in nature. A number of other techniques are also listed in the project's guidebook with possible impacts on pedestrian safety, however no information was found in the literature regarding definite impacts (Kittelson & Associates, Inc. Read the entire page →
From page 193... ... 193  Directional pedestrian volumes on both crosswalks  Traffic signal cycle length  Timing information for the pedestrian phases for both crosswalks Crosswalk Circulation Area Corner circulation area measures the average space available for pedestrians crossing a street in one direction of travel. This measure can be used to evaluate existing conditions or as part of a design application, identifying the crosswalk with required to serve a particular pedestrian demand at a desired QOS. Read the entire page →
From page 194... ... 194 Pedestrian Delay Pedestrian delay measures the average wait time from the time a pedestrian arrives at a street corner to when the pedestrian is able to enter the crosswalk. The measure had LOS letters associated with it in the 1985 and 2000 editions of the HCM (A = <10 s, B = ≥10–20 s, C = >20–30 s, D = >30–40 s, E = >40–60 s, and F = >60 s) Read the entire page →
From page 195... ... 195 intersections the raters would walk through later; the researchers found there was a difference between video and in-field ratings and adjusted the video ratings accordingly. The inclusion of the video clips allowed right-turn channelizing islands to be included in the model. Read the entire page →
From page 196... ... 196  Number of travel lanes being crossed (including turn lanes)  Number of right-turn channelizing islands encountered on the crossing  Traffic volume per 15 minutes traveling over the crosswalk  Right-turn-on-red volume per 15 minutes conflicting with pedestrian movements  Permitted left-turn volume per 15 minutes conflicting with pedestrian movements  Midblock 85th percentile traffic speed on the street being crossed  Pedestrian delay To test sensitivity, a base intersection was defined with the following attributes:  Number of travel lanes crossed: 5  Number of right-turn channelizing islands: 0  Outside lane traffic flow rate: 500 veh/h  Right-turn-on-red volume per 15 minutes: 10 veh  Permitted left-turn volume per 15 minutes: 40 veh  Midblock traffic speed: 30 mph  Pedestrian delay: 35 sec (comparable to 90-second cycle length with 10-second effective pedestrian walk time) Read the entire page →
From page 197... ... 197 (a) Delay (b) Read the entire page →
From page 198... ... 198 Urban Street Segments Chapter 18 of the HCM 6th Edition (TRB 2016) presents methods for estimating pedestrian LOS for an urban street segment, a street section bounded by intersections where motorized vehicle traffic may have to stop. Read the entire page →
From page 199... ... 199 et al. Read the entire page →
From page 200... ... 200 To test sensitivity, a base street was defined with the following attributes:  Outside through travel lane width: 12 feet  Parking lane width: 0 feet  Bicycle lane width: 0 feet  Percent on-street parking occupied: 0%  Buffer width: 0 feet  Sidewalk width: 6 feet  Outside lane flow rate: 500 veh/h  Motor vehicle running speed: 30 mph  Street trees: no One attribute was varied at a time to determine the resulting pedestrian link LOS score, which can be used to determine a pedestrian LOS letter for the link. Figure A2 shows the results. Read the entire page →
From page 201... ... 201 It can be seen that pedestrian LOS for links is  Relatively insensitive to roadway lane widths, traffic speed, landscape buffer width, and sidewalk width (except when installing a sidewalk where none existed previously) ;  Moderately sensitive to the percentage of occupied on-street parking and the presence of street trees; and  Highly sensitive to traffic volume. Read the entire page →
From page 202... ... 202 the middle of the possible range of delays (approximately 20–50 seconds) , but the same segment LOS when delays are very low, or are greater than or equal to 60 seconds. Read the entire page →
From page 203... ... 203 The final model requires less data collection and is capable of predicting the probability of a user selecting each LOS letter for a given set of conditions. Testing of the model indicating it had a tendency to underpredict the number of LOS A ratings (Ali et al. Read the entire page →
From page 204... ... 204 (i.e., pedestrian segment LOS score) LOS, with the lower of the two LOS letters being reported as the LOS result for the urban street segment. Read the entire page →
From page 205... ... 205 (a) Average flow (b) Read the entire page →
From page 206... ... 206 computational engine for the method was developed by NCHRP Project 03-92, but has not been posted on HCM Volume 4 by decision of the TRB Highway Capacity Committee (to avoid the need to provide user support and training for this and other spreadsheet-based computational engines) Read the entire page →
From page 207... ... 207 (a) Traffic volume, 0% yielding (b) Read the entire page →
From page 208... ... 208 vehicular headway for the first yielding event. The vehicular headway decreases as vehicular volumes increase, which would account for the shape of the curve. Read the entire page →
From page 209... ... 209  Illumination presence  General land use  Roadway crossings:  Functional class  Number of travel lanes  Posted speed  Roadway average daily traffic (optional)  Sidewalk ramp presence  Median refuge presence  Illumination presence  General signalized intersection features Four PLTS are defined (Oregon DOT 2017) Read the entire page →
From page 210... ... 210 In a systematic review of 58 studies on PLOS, Raad and Burke (2018) make several observations. Read the entire page →
From page 211... ... 211 provided methods for arterial and collector streets. The NCHRP Project 03-70 panel and researchers accepted the premise that the project's multimodal methods should only address urban arterials and collectors (Dowling et al. Read the entire page →
From page 212... ... 212 Table A11. Limitations of Current HCM Pedestrian Methods. Read the entire page →
From page 213... ... 213 Summary Techniques for Efficient and Accurate Estimation of Pedestrian Volume and Exposure The most commonly used technologies for counting pedestrians at present are manual counts in the field and manual counts from video. When automated counts are used, passive infrared, active infrared and automatic counts from video are the most common methods (FHWA 2011, Ryus et al. Read the entire page →
From page 214... ... 214 Table A12. Key Factors Affecting Pedestrian Crash Frequency. Read the entire page →
From page 215... ... 215 and fumes, pedestrian flow rate, waiting time, crossing distance) ; aesthetics (sidewalk cleanliness and surface quality, presence of obstructions, presence of trees) Read the entire page →
From page 216... ... 216 Factors Effect on Pedestrian Operations Unsignalized Crossings Marked crosswalks May improve driver yielding rate, thereby reducing crossing delay. If a crosswalk provides a new legal crossing opportunity that did not exist before, could improve pedestrian link and segment LOS due to the midblock crossing opportunity Advance YIELD/STOP signs May improve driver yielding rate High-visibility crosswalks May improve driver yielding rate Pedestrian hybrid beacons May improve pedestrian LOS by reducing street-crossing delay, compared to waiting for a gap in traffic Rectangular rapid-flashing beacons May improve driver yielding rate Median refuge, raised median If sufficiently wide to store pedestrians, allows for two-stage crossings, with overall lower delay (improves LOS) Read the entire page →
From page 217... ... 217 HCM exhibit relating ranges of pedestrian space values for queuing areas at street corners uses values for moving pedestrians (e.g., along sidewalks) rather than for standing pedestrians, which appears to be an error. Read the entire page →
From page 218... ... 218 References Akçelik & Associates Pty. Read the entire page →
From page 219... ... 219 Campbell, B.J., C.V. Zegeer, H.H. Read the entire page →
From page 220... ... 220 Dutata, N., Q Zhang, and M Read the entire page →
From page 221... ... 221 Fitzpatrick, K., S Turner, M Read the entire page →
From page 222... ... 222 Hankin, B.D., and R.A. Wright. Read the entire page →
From page 223... ... 223 Jung, H., S Read the entire page →
From page 224... ... 224 Loukaitou-Sideris, A., R Liggett, and H.G. Read the entire page →
From page 225... ... 225 Nazir, M.I., S.K. Adhikary, Q.S. Read the entire page →
From page 226... ... 226 Raad, N., and M.I. Burke. Read the entire page →
From page 227... ... 227 Schneider, R., M Diogenes, L Read the entire page →
From page 228... ... 228 Turner, S., I Sener, M Read the entire page →
From page 229... ... 229 Young, S.B. Read the entire page →

From page 168...

... 168 Appendix A: Literature Review Introduction This appendix presents the literature review for NCHRP Project 17-87, "Enhancing Pedestrian Volume Estimation and Developing HCM Pedestrian Methodologies for Safe and Sustainable Communities," summarizing information relevant to the project objectives from over 300 reviewed documents. Because members of the project team have performed literature reviews for other related projects in the recent past, the information obtained from the following reviews was used as a starting point for this review:  NCHRP Project 17-84, "Pedestrian and Bicycle Safety Performance Functions for the Highway Safety Manual";  NCHRP Project 07-19, "Methods and Technologies for Collecting Pedestrian and Bicycle Volume Data";  NCHRP Project 07-17, "Pedestrian and Bicycle Transportation Along Existing Roads";  NCHRP Project 17-73, "Systemic Pedestrian Safety Analysis";  NCHRP Project 15-63, "Guidance to Improve Pedestrian and Bicycle Safety at Intersections";  NCHRP Project 03-120, "Assessing Interactions Between Access Management Treatments and Multimodal Users";  NCHRP Project 07-25, "Guide for Pedestrian and Bicycle Safety at Alternative Intersections and Interchanges (A.I.I.)