Enhancing Pedestrian Volume Estimation and Developing HCM Pedestrian Methodologies for Safe and Sustainable Communities (2022) / Chapter Skim
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24 Chapter 3. Research Approach Introduction This chapter documents the approach used to investigate three aspects of pedestrian QOS: Pedestrian satisfaction crossing roadways, with and without the presence of selected pedestrian safety countermeasures; Updating the HCM 6th Edition pedestrian delay estimation methods for signalized and unsignalized crossings; and Investigating methods for evaluating pedestrian network QOS.
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25 Next, working from the identified treated locations, the team selected ten locations for each treatment type, seeking to represent a spectrum of road and traffic conditions. The team aimed to have a mix of two- to three-lane crossings and four- to five-lane crossings for the unsignalized sites (i.e., RRFB and control sites, Median Island and control sites)
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26 Table 3-1. RRFB Treated and Control Crossing Sites.
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27 Table 3-2. Median Island Treated and Control Crossing Sites.
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28 Table 3-3. LPI Treated and Control Signalized Crossing Sites.
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29 Site Crosssection And Median Type Treated/ Control Vehicle Travel Directions Major Road AADT Number of Through Lanes on the Street Being Crossed Posted Speed Limit (mph) NE Broadway St and NE 9th St Intersection, marked, undivided Control one-way 18,859 3 30 NE Broadway St and NE 32nd St LPI, intersection, marked, undivided Treated one-way 18,859 4 30 NE Broadway St and NE 28th St Intersection, marked, undivided Control one-way 17,359 4 30 E Burnside and 20th St LPI, intersection, marked, undivided Treated two-way 17,359 3 30 E Burnside and 28th St Intersection, marked, undivided Control two-way ~10,000–15,000 3 30 SE Hawthorne and SE 50th St LPI, intersection, marked, undivided Treated two-way 14,976 2 20 Speed Study To investigate how vehicle speeds might correlate with posted speed limits and whether vehicle speeds traveling uphill might be different from vehicle speeds traveling downhill, a LIDAR speed study was conducted at the RRFB crosswalk near the Chapel Hill Town Hall on Martin Luther King Jr.
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30 Base image source: © 2019 Google Figure 3-1. Distance Measurements for LIDAR Speed Gun Data Collection.
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31 Figure 3-2. Histogram of Motorist Speeds at RRFB Crossing of Martin Luther King Jr.
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32 pedestrians actuated the RRFB push-button, the degree to which they appeared distracted, and their apparent gender and group size. The full pedestrian crossing survey is provided in Appendix C
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33 Figure 3-3. Extendable Pole with Camera Attached and Battery Pack, Chapel Hill (left)
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34 Image sources: HSRC (left, right) , © 2019 Google (center)
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35 Image sources: HSRC (left) , © 2019 Google (right)
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36 Table 3-5. Response Rates at RRFB and RRFB Control Survey Sites.
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37 Table 3-6. Response Rates at Median Island and Median Island Control Survey Sites.
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38 Table 3-7. Response Rates at LPI and LPI Control Survey Sites.
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39 Table 3-8. Crosswalk Intercept Survey Response Summary.
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40 b12 is the coefficient of the second independent variable x2 is the second variable (in this case, a categorical variable set to class 2) ; b1n is the coefficient of the nth variable; and xn is the nth variable (in this case, a numeric rather than categorical variable)
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41 the variables loaded onto that factor (revealed by the presence of positive or negative correlations) , those variables could then be averaged to create a new variable for the latent factor in the data.
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42 and the volume of turning traffic. Figures 3-7 and 3-8 show an example of the view of each camera at a location in Chapel Hill.
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43 Figure 3-8. Camera Angles and Screenshots of Eastern LPI Crosswalk on Raleigh Rd and Hamilton Rd, Portland.
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44 traffic. Behaviors such as waving, gesturing negatively to drivers, or using a wheelchair, walker, skateboard, scooter, or roller skates were coded.
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45 Talking with others crossing Talking on cell phone Looking at cell phone/device/other Not engaged with device/others A pedestrian wearing headphones/earbuds was initially coded as a behavior but was removed from the coding template due to difficulty observing this phenomenon from the videos. Coding Bicycle and Motor Vehicle Interactions with Pedestrians Interactions were coded for each cyclist or motorist approaching the crosswalk during a pedestrian crossing.
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46 Signalized Video Coding The coding procedure was different for crosswalks at signalized intersections (LPI and non-LPI locations)
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47 Coders also counted the motor vehicle volume (i.e., the number of vehicles) from the time the WALK signal turned on until the end of the parallel green phase.
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48 Table 3-9. RRFB and Control Sites Video Data Collection.
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49 Table 3-10. Median Island Treated and Control Sites Video Data Collection.
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50 Table 3-11. LPI Treated and Control Sites Video Data Collection.
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51 Naturalistic Walking Study Purpose The primary purpose of the naturalistic walking study was to validate intercept survey and video observation data obtained during Task 6D at selected roadway crossing locations in Chapel Hill, NC. A secondary purpose was to discern pedestrian QOS based on physiological measurements of pedestrians performing normal walking activities in different traffic contexts.
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52 Researchers monitored participants' use of the GPS and Empatica devices daily (all participants appeared to make use of them each day)
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53 Accelerometer, which measures acceleration along three axes at 5-second intervals; these data were collected but not used for this study, in part because the measurement interval was too crude for the study's purposes. Thermometer, which measures skin temperature; these data were collected but not used for this study.
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54 Figure 3-10. Example Visualization of a Participant's Walking Trip, with Time- and Location-bound EDA and HR Readings.
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55 Estimating Pedestrian Delay Uncontrolled Crossings This section describes proposed revisions to the pedestrian delay prediction methodology in Chapter 20 of the HCM 6th edition. This methodology is used to predict pedestrian delay at two-way stop-controlled (TWSC)
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56 crossing and the two delay values are added to produce the total delay incurred when crossing the street. The calculation sequence for the remaining steps is summarized below to facilitate the subsequent discussion of the proposed changes.
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57 Finally, the group critical headway is computed using the following equation.
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58 Step 5: Estimate Delay Reduction due to Yielding Vehicles When a pedestrian arrives at a crossing and finds the vehicle headway is shorter than needed to cross, that pedestrian is delayed until either a headway greater than the critical headway is available, or motor vehicles yield and allow the pedestrian to cross. Equation 7 estimates pedestrian delay when motorists on the major approaches do not yield to pedestrians.
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59 where My = motorist yield rate (decimal) , and i = crossing event (i = 1 to n)
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60 Table 3-12. Summary of Motorist Yield Rates for Alternative Pedestrian Crossing Treatments.
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61 Treatment Study Location Number of Sites Motorist Yield Rate (%) {reported range]
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62 Treatment Study Location Number of Sites Motorist Yield Rate (%) {reported range]
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64 where Np = spatial distribution of pedestrians (pedestrian rows) , Wc = crosswalk width (ft)
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65 Database Development This section provides an overview of the database and data collection procedures as well as a summary of the collected data. Each observation in the database represents traffic conditions and traveler behavior just prior to (and after)
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66 Pedestrian delay is defined in the HCM as the time the pedestrian waits to start the crossing. One delay value was recorded for each observation.
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67 Major Street Minor Street Vehicle Movements Pedestrian Movements 5 2 4P 3 8 2P 1 6 8P 74 6P 6 8 2 4 Corner A Corner BCorner C Corner D and (3) random arrivals over an large number of signal cycles can be modeled deterministically using a uniform arrival rate.
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68 Corner A 8 122 4 656 Corner BCorner C Corner D 34 78 D4 B12 C12 B2 D56 A6 D6 A56 D34 C2 C34 C4 A78 A8 B8 B78 Based on the preceding explanation of traffic movement numbers and signal phases, the delay to pedestrian movement 2P is based on the cycle length C and the effective walk time for phase 2 gWalk,2. This delay is computed using Equation 17.
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69 (other than those indicated by the numbers shown in Figure 3-12a) provided that the phase settings are such that conflicting vehicular movements will not time concurrently.
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70 𝑃𝐷𝑊1 = (𝐶 − 𝑔Walk, 𝑖) 𝐶 Equation 19 where C = cycle length (s)
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71 A8A8B2 D6A8 B2 B2C4 A8B2 C4 C4D6 B2C4 D6 D6A8 C4D6 B8B8A6 C2B8 C2 C2B8 D4C2 D4 D4C2 A6D4 A6 A6D4 B8A6 6 8 2 4 Corner A Corner BCorner C Corner D Figure 3-13a shows the number assigned to each crosswalk for the case where the crosswalk is crossed in one phase. The crosswalk numbers shown are the same as in Figure 3-11a.
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72 The first letter and first number in each pedestrian movement label are interpreted together. The first letter in each label indicates the corner at which the pedestrian began the crossing maneuver.
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73 an overall error (i.e., difference between the predicted and observed delays)
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74 If the crossing direction is clockwise (i.e., from corner B to corner C) and phase 1 lags phase 2 in the phase sequence and, then Phase X is phase 2 and Phase Y is phase 2.
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75 PCi = pedestrian clear duration for phase i (s)
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76 Protected Movement Permitted Movement Pedestrian Movement Φ1 Φ2 Φ3 Φ4 Φ5 Φ6 Φ7 Φ8 Barrier Ring 1 Ring 2 Barrier Time 1 6P 65 2 2P +12 3 7 4P 4 8 8P 0 CDp1 Dp1+Dp2 Dp1+Dp2+Dp3 12 (i.e., Y = 2)
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77 Step 5. Compute Delay for Second-Stage Crossing Given Arrival Is During Don't Walk During this step, the second-stage crossing delay is computed for one portion of the pedestrian stream.
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78 There are two sets of equations that can be used to compute the second-stage crossing delay. The correct set of equations is determined by comparing the value of t with the effective walk time for Phase X
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79 with 𝑃𝐷𝑊1 = (𝐶 − 𝑔Walk,X) 𝐶 Equation 33 where dp = pedestrian delay (s/p)
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80 provide pedestrian service. The first phase to serve travel in the other direction is denoted by the letter "Z" (i.e., Phase Z is the first phase to serve the pedestrian starting the diagonal crossing in a direction opposite to the direction of interest)
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81 𝑔𝑊𝑎𝑙𝑘,𝑖 = 𝐷𝑝,𝑖 − 𝑌𝑖 − 𝑅𝑐,𝑖 − 𝑃𝐶𝑖 + 4.0 Equation 35 where Dp,i = duration of phase i (s) , Yi = yellow change interval duration for phase i (s)
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82 Φ1 Φ2 Φ3 Φ4 Φ5 Φ6 Φ7 Φ8 Barrier Ring 1 Ring 2 Barrier 1 6P 65 2 2P 3 7 4P 4 8 8P 0 CDp1 Dp1+Dp2 Dp1+Dp2+Dp7 Dp1+Dp2+Dp3 Figure 3-15. Example Phase Sequence for Diagonal Crossing Shown Using Dual-ring Structure.
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83 where TZ = relative end time of the effective walk period for Phase Z (s) , TWalk,Z = relative start time of the Walk interval for Phase Z (s)
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84 Step 6. Compute Delay for Second-Stage Crossing During this step, the delay for the second-stage crossing in the subject travel direction is computed.
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85 Midsegment Crossing LOS This section provides an overview of two methodologies that can be used to evaluate the pedestrian's level of difficulty when crossing a street segment. Each methodology is described in a separate subsection.
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86 conditions near the segment and to then rate segment LOS on a six-point scale that ranged from A (best) to F (worst)
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87 Table 3-13. Pedestrian LOS and Delay Thresholds.
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88 𝑑𝑝𝑑,𝐿𝑂𝑆 = 0.084 2 𝐷𝑐 𝑆𝑝 + 𝑑𝑝𝑐 Equation 50 where dpd,LOS is the LOS-based pedestrian-perceived diversion delay (s/p) and all other variables are as previously defined.
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89 Ip,mx = pedestrian LOS score for midsegment crossing. If the factor obtained from Equation 51 is less than 0.80, the factor is set equal to 0.80.
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90 The third value is the delay incurred by pedestrians who travel through the boundary intersection along a path that is parallel to the segment centerline dpp. Equation 47 is also used for this calculation; however, the pedestrian service time value is based on the green interval duration for the major street through movement.
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91 a poor link LOS on segment LOS. They argued that the link and intersection LOS scores should be computed as a weighted average of their respective "exposure times." For links, the exposure time was computed as the link travel time and for intersections, the exposure time was computed as the delay incurred by pedestrians who travel through the boundary intersection along a path that is parallel to the segment centerline dpp.
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92 determine the LOS score for waiting delay Ipw. When either delay value is between the range limits shown in the table, interpolation is used to estimate the corresponding LOS score.
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93 To help decide which factors could be incorporated into a pedestrian network connectivity QOS measure, the research team conducted a focused literature review on the available measures and methodologies for evaluating the QOS of a pedestrian network. The research team investigated pedestrian, bicycle, and transit network connectivity measures, and pedestrian and bicycle LOS and level of traffic stress (i.e., quality)
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94 Measure Description Source Pedestrian route directness Route distance over straight-line distance. Hess 1997, Randall and Baetz 2001, Tal.
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95 Measure Description Source Heavy vehicle traffic Percent heavy vehicles. Clifton et al.
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96 Table 3-15. Methods Related to Pedestrian QOS Used in Planning Literature Method Description Source Pedestrian Index of the Environment (PIE)
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97 calculated for roadway segments and intersections. The research team obtained readily available data on the roadway characteristics and pedestrian attributes used by both these measures in the form of GIS shapefiles for the entire state of Florida.
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98 Table 3-16. Pedestrian LOS Score Thresholds.
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99 Table 3-17. Sidewalk Condition.
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