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28 should be improved to incorporate the effects of signal coor- Byrd and Sisiopiku [52] compared the more commonly dination. accepted methods of determining pedestrian LOS for side- Clark et al. [46] developed a pedestrian LOS method based walks, including the HCM 2000, Landis, Australian, and Trip on discrete pedestrian crossing outcomes: non-conflicting, Quality methods. The comparison found that it is possible compromised, and failed. Their case study results found that to receive multiple LOS ratings for the same facility under the greatest incidence of failed and compromised pedestrian the same conditions from these methods and the paper crossings was observed was a moderately high number of concludes that a combined model could be developed that vehicular right turns were served by an exclusive right-turn synthesizes the quantitative and qualitative factors that affect lane that subtended an obtuse angle with a large turning pedestrian operations. radius. Muraleetharan and Hagiwara [53] used a stated prefer- Lee et al. [47] also looked at crossing LOS using a stated- ence survey to identify the variables most important to a preference survey. They found that the key determinants of pedestrian's perception of the utility of the walking envi- LOS at signalized intersections were area occupancy, pedes- ronment. A revealed preference survey with 346 respon- trian flow, and walking speed. Similarly, Muraleetharan et al. dents was used to develop a utility model that predicts [48] identified the factors that describe pedestrian LOS at which route a pedestrian will prefer to walk. LOS A was as- crosswalks and found that the most important factor was the signed to the maximum computed utility among all of the presence of turning vehicles. While confirming these find- sidewalks and crosswalks evaluated. LOS F was assigned to ings, Petritsch et al. [49] provided additional insights into the lowest computed utility among all of the sidewalks and the critical factors that determine pedestrians' perceptions of crosswalks evaluated. LOS at signalized intersection crossings. They found that Muraleetharan et al. [48] found that the "flow rate" is the right-turn-on-red volumes for the street being crossed, per- most important factor that determines pedestrian LOS on missive left turns from the street parallel to the crosswalk, sidewalks. Hummer et al. [54] studied pedestrian path oper- motor vehicle volumes on the street being crossed, midblock ations and found that the path width, the number of meeting 85 percentile speed of the vehicles on the street being and passing events, and the presence of a centerline were the crossed, the number of lanes being crossed, the pedestrian's key variables that determined pedestrian path users' percep- delay, and the presence or absence of right-turn channeliza- tions of quality of service. However, Patten et al. [55] noted tion islands were primary factors for pedestrians' LOS at that when paths are shared between pedestrians and bicy- intersections. clists, estimating LOS for each user group and designing a new facility to the appropriate width and whether to separate these different users on the right-of-way becomes difficult. Sidewalk and Path LOS Studies Sponsored by FHWA, they developed a bicycle LOS estima- Other studies focused on measuring pedestrian LOS on tion method for shared-use paths to overcome these limita- sidewalks or paths. Analysis of the results of these studies sug- tions by integrating a path user perception model with path gests that the most important variables that determine pedes- operational models developed in the project's earlier phases. trian LOS--and therefore, the very definition of pedestrian Petritsch et al. [56] found that traffic volumes, a sidewalk's LOS itself--change depending on the context. adjacent roadway width, and the density of conflict points As described in more detail under the bicycle LOS model along it (e.g., the number of driveways) are the most impor- section, Jensen [50] used video lab observations to develop a tant factors determining pedestrian LOS along urban arteri- pedestrian segment LOS model for Denmark. als with sidewalks. Bian et al. [51] conducted a sidewalk intercept survey to Taking a step back to revise the theoretical perspective on measure pedestrian perceptions of sidewalk LOS in Nanjing, pedestrian LOS, Muraleetharan et al. [57] used conjoint analy- China. A total of 501 people were interviewed on nine sidewalk sis to develop a pedestrian LOS method based on total utility segments. They identified lateral separation from traffic, motor value. They found that total utility value can be used as an index vehicle volume and speed, bicycle volume and speed, pedes- of pedestrian LOS of sidewalks and crosswalks. trian volume, obstructions, and driveway frequency as the fac- Sisiopiku et al. [58] reviewed recent research on pedes- tors influencing pedestrian LOS. They defined LOS 1 as "ex- trian level of service. Their critique can be summed up as cellent," LOS 2 through 6 are "good," "average," "inferior," follows: "poor," and "terrible," respectively. A linear regression model was fitted to the data to predict the mean LOS rating. The nu- 1. Non-HCM methods need to take into account the effect merical score predicted by the model was converted to a letter of platooning on pedestrian LOS. grade using the following limits: LOS A <= 1.5, LOS B <= 2.5, 2. All methods need to consider a variety of pedestrian LOS C <= 3.5, LOS D <= 4.5, LOS E <= 5.5. groups. Different groups have different needs.