METHODS OF ASSESSING PEDESTRIAN LEVEL OF SERVICE

Transcription

1 ABSTRACT Research Article METHODS OF ASSESSING PEDESTRIAN LEVEL OF SERVICE Singh K.*, Jain P.K.** Address for Correspondence *Asst. Professor, Department of Civil Engineering Maulana Azad National Institute of Technology (MANIT), Bhopal 46205, India **Associate Professor, Department of Civil Engineering Maulana Azad National Institute of Technology (MANIT), Bhopal 46205, India Pedestrians form the largest single road user group and also are the most vulnerable road users. Pedestrians movements are not restricted to lanes or specific routes however they are restricted by the physical boundaries around them such as the presence of walkways or pedestrian ways. Therefore the needs of the pedestrian should be considered in the design of transportation facilities. Pedestrian facilities include sidewalks, paths, crosswalks, stairways, curb cuts and ramps, and transit stops. In some areas, particularly in suburban and rural communities, pedestrians may be sharing the roadway itself or its shoulders. These facilities should be pedestrian friendly to promote walking and safety of the pedestrians. To know how well roadways accommodate pedestrian travel or how they are pedestrian friendly it becomes necessary to assess the walking conditions. Such a measure of walking conditions would be helpful in roadway cross-sectional design. It would also help evaluating and prioritizing the needs of existing roadways for sidewalk retrofit construction. Estimation of pedestrian level of service (LOS) is the most common approach to assess quality of operations of pedestrian facilities. The focus of this study is to review current methods of assessing pedestrian level of service (PLOS) and discussing some new concepts which have been proposed by the researchers to evaluate pedestrian environment in a better way. KEY WORDS: Sidewalks, pedestrian level of service, pedestrian environment, unit flow rate, satisfaction rating. INTRODUCTION subjected to diverse factors which affect A significant proportion of every modal trip is made by walking. Therefore the needs of the pedestrian, like the needs of motor vehicles, should be considered in the design of the urban environment and transportation facilities. Efforts should be directed toward the safe, accessible, and convenient mobility for pedestrians. Also residents and visitors should be encouraged to walk for trips of reasonable length. Evaluating the pedestrian facilities and walking conditions is much more complex than the vehicular roadway, because while occupants of automobiles are separated in their insulated environment, the pedestrian is exposed to a variety of diverse environmental conditions. Dan Burden states that the pedestrian in the roadside environment is his/her feeling of safety, comfort, and convenience. (Burden, Dan 996). Pedestrian LOS is an overall measure of walking conditions on a route, path, or facility. In this paper current practices for providing pedestrian facilities and methodologies of assessing level of service (LOS) for pedestrians are discussed. Their strengths and weaknesses are examined and suggestions are made to arrive at a more satisfactory service level analysis of pedestrian facilities. By understanding and going beyond existing LOS methodologies, the transportation planners and managers can think for an appropriate methodology that adequately assesses the service level for walking.

2 PEDESTRIAN LEVEL OF SERVICE Level of Service (LOS) in transportation engineering is a term used which describes existing operating conditions (or suitability) for a mode of travel in a transportation system. Motor vehicle LOS is primarily based on speed, travel time, and intersection delay. Calculation of Pedestrian LOS is more complex, which represents the operating condition of pedestrian facility and level of comfort pedestrians experience in using these facilities. METHODS OF EVALUATING PEDESTRIAN LEVEL OF SERVICE The current practices for evaluating pedestrian facilities can be grouped into two types (i) Capacity Based Methods- HCM Method (ii) Roadway Characteristics Based Methods- Pedestrian Environment Factors Capacity based methods use the principles of highway capacity which have been suitably adjusted to evaluate pedestrian facilities. They are helpful in planning pedestrian facilities but provide little information regarding acceptability by pedestrians. Roadway Characteristics Based Methods are based on the characteristics of the walkways or pedestrian facilities. These methods use pedestrian perceptions and attempt to quantify the comfort level of pedestrians while encountering certain roadway characteristics. HCM METHOD OF PEDESTRIAN LOS The HCM s methods for analyzing pedestrian LOS are based on the measurement of pedestrian flow rate and sidewalk space. The pedestrian flow rate incorporates pedestrian speed, density, and volume, which is equivalent to vehicular flow. According to the Highway Capacity Manual (HCM): As volume and density increase, pedestrian speed declines. As density increases and pedestrian space decreases, the degree of mobility afforded to the individual pedestrian declines, as does the average speed of the pedestrian stream. Assesment of the sidewalk level of service uses the calculation of pedestrians per minute per foot (ped/min/ft) as the basis for LOS classification as shown in the Table- and Table-2. According to this measurement, on a sidewalk or walkway with LOS A, pedestrians move freely without altering their speed in response to other pedestrians or to a decrease in the sidewalk width. On the other hand, on a sidewalk or walkway with LOS F, all walking speeds are severely restricted and forward progress is made only by shuffling. (See Figures for the HCM s description for each pedestrian LOS) The pedestrian unit flow rate (ped/min/ft) is obtained by taking the pedestrian 5-minute flow rate (ped/5-min) and dividing by the effective sidewalk width. For calculating pedestrian flow rate, the HCM suggests collecting pedestrian opposing flow volumes at 5-minute intervals. The sum of the two directional flows is used as the 5-minute flow rate. Effective width of the sidewalk used in the calculation is obtained by taking the total width of the sidewalk and subtracting obstacle widths and a to.5 ft buffer width per obstacle. Obstacle widths can be measured from the field. The HCM procedure for buffer width calculation is based on Pushkarev and Zupan (975).

3 Sidewalk Level..of Service LOS A LOS B LOS C LOS D LOS E Table-: Sidewalk Level of Service Classification Characteristics of Sidewalk Pedestrian Space > 60 ft²/p, Flow Rate = 5 p/min/ft, pedestrians move in desired paths without altering their movements in response to other pedestrians. Walking speeds are freely selected, and conflicts between pedestrians are unlikely. Pedestrian Space > ft²/p, Flow Rate > 5-7 p/min/ft, there is sufficient area for pedestrians to select walking speeds freely to bypass other pedestrians, and to avoid crossing conflicts. At this level, pedestrians begin to be aware of other pedestrians, and to response to their presence when electing a walking path. Pedestrian Space > ft²/p, Flow Rate > 7-0 p/min/ft, space is sufficient for normal walking speeds, and for bypassing other pedestrians in primarily unidirectional streams. Reverse-direction or crossing movements can cause minor conflicts, and speeds and flow rate are somewhat lower. Pedestrian Space > 5-24 ft²/p, Flow Rate > 0-5 p/min/ft, freedom to select individual walking speed and to bypass other pedestrians is restricted. Crossing or reverse-flow movements face a high probability of conflict, requiring frequent changes in speed and position. The LOS provides reasonably fluid flow, but friction and interaction between pedestrians is likely Pedestrian Space > 8-5 ft²/p, Flow Rate > 5-23 p/min/ft, virtually all pedestrians restrict their normal walking speed, frequently adjusting their gait. At the lower range, forward movement is possible only by shuffling. Space is not sufficient for passing slower pedestrians. Cross- or reverse-flow movements are possible only with extreme difficulties. Design volumes approach the limit of walkway capacity, with stoppages and interruptions to flow. LOS F Pedestrian Space = 8 ft²/p, Flow Rate varies p/min/ft, all walking speeds are severely restricted, and forward progress is made only by shuffling. There is frequent unavoidable contact with other pedestrians. Cross-and reverse-flow movements are virtually impossible. Flow is sporadic and unstable. Space is more characteristic of queued pedestrians than of moving pedestrian streams. Pedestrian LOS for sidewalks and sideways is speed (ft/s), and the volume-to-capacity (v/c) calculated using the pedestrian unit flow rate. In addition to LOS grades A to F, space (ft²/p), Table-2: PLOS Criteria (HCM 2000) ratio can also be derived from the Table-2. LOS Space (ft 2 /ped.) Flow Rate Speed (ft/sec) V/C Ratio (Ped./min/ft) A >60 5 > B >40-60 >5-7 > > C >24-40 >7-0 > > D >5-24 >0-5 > > E >8-5 >5-23 > > F 8 Variable 2.50 Variable

4 The HCM method though simple to apply but it suffers serious setbacks in relating the performance of sidewalk with various qualitative dimensions of walking such as footpath surface condition, walking environment, comfort, safety and potential for vehicle conflict. The HCM attempts to make walking an equal among all transport modes, but it does so only on its terms of service measures. Speed is one of the important criteria used for LOS determination which shows motor vehicle bias of the pedestrian LOS methodology. Pedestrians are treated as vehicles on legs or object moving in horizontal space and the methodology is based on American study only without adjustments for other cultural context. SCI MODEL OF PEDESTRIAN LOS Sprinkle Consulting, Inc. (SCI) has developed a model to predict pedestrian level of service (Landis et al., 200). The model was developed through a multi-variable regression analysis based on observations from the 42 directional segments in the Pensacola metropolitan area. The model and its pedestrian LOS predictions are based on perceived safety relative to traffic conditions. Primary factors (independent variables) that determine the LOS of safety (or comfort) include lateral separation elements between pedestrians and motor vehicle traffic (such as presence and width of sidewalk, presence of on-street parking or bike lane, width of outside travel lane), motor vehicle traffic mix, volumes, and speeds. Given a complete data set (or assumptions) for the used independent variables, the model is said to predict perceived safety (or comfort) vis-à-vis motor vehicle traffic. The following Model was developed to calculate pedestrian level of service (PLOS): Ped LOS = ln (Wol+ Wl + fp x%osp + fb x Wb + fsw x Ws) ln (Vol5/L) SPD (2) Where: Wol = Width of outside lane (feet) Wl = Width of shoulder or bike lane (feet) fp = On-street parking effect coefficient (=0.20) %OSP = Percent of segment with on-street parking fb = Buffer area barrier coefficient (=5.37 for trees spaced 20 feet on center) Wb = Buffer width (distance between edge of pavement and sidewalk, feet) fsw = Sidewalk presence coefficient = 6 0.3Ws Ws = Width of sidewalk (feet) Vol5 = average traffic during a fifteen (5) minute period L = total number of (through) lanes (for road or street) SPD = Average running speed of motor vehicle traffic (mi/hr) The model seems to be a convenient and useful tool for evaluating various roadside walking segments but it has following major limitations:-. The model is based on observations gathered at a one-time event only. The model needs to be tested with different groups of people under varying time events 2. All the observations were made by 75 people. Results from such a small sample size can not be generalized for large population. 3. The model does not predict LOS as a measure of ease of pedestrian movement on walkway segments. It rather predicts a motor vehicle exposure rating from a pedestrian perspective. 4. The model has been developed for roadway segments only. Intersections have not been considered

5 5. The aesthetic quality of the walking environment has a considerable influence on one s perception of safety (or comfort) but in their study participants were performance measures for the Gainesville, Florida roadway uses a point system of to 2 that results in LOS ratings from A and F (Table-3 and Table-4). The scoring system encouraged to disregard surroundings was developed with sensitivity to aesthetics. characteristics that may be mutually exclusive 6. The model ignores actual sidewalk usage. or inclusive to determine all possible 7. The model predicts perceived safety (or comfort) and has not been correlated with actual safety data. combinations of points. Pedestrian LOS ratings are defined by the measures of pedestrian safety features and the level of GAINESVILLE PEDESTRIAN LOS automobile-oriented development PERFORMANCE MEASURES The method developed by Dixon, Linda B. (996) for bicycle and pedestrian LOS characteristics along the corridor. The LOS ratings describe the degree to which facility provisions encourage pedestrian use. Table-3: Pedestrian Level-of-Service (Dixon, 996) Category Criteria Points Pedestrian Facility (Max. value = 0) Not continuous or non-existent Continuous on one side Continuous on both sides Min..53 m (5 ) wide & barrier free Sidewalk width >.53 (5 ) Off-street/parallel alternative facility Conflicts (Max. value = 0) Driveways & side streets Ped. Signal delay 40 sec. or less Reduced turn conflict implementation Crossing width 8.3 m (60 ) or less Posted speed Medians present Amenities (Max. value = 2) Buffer not less than m (3 5 ) Benches or pedestrian scale lighting Shade trees Motor Vehicle LOS (Max. value = 2) LOS = E, F, or 6+ travel lanes LOS = D, & < 6 travel lanes LOS = A, B, C, & < 6 travel lanes 0 2 Maintenance (Max. value = 2) Major or frequent problems Minor or infrequent problems No problems TDM/Multi Modal (Max. value = ) No support Support exists 0

6 Table-4: Pedestrian Level of Service Ratings (Dixon, 996) LOS Rating Points A >7 B >4-7 C >-4 D >7- E >3-7 F 3 or less. The methodology is based on the hypothesis that there is a critical mass of variables that must be present to attract non motorized trips. The methodology is applicable for corridor evaluations on arterial and collector roadways in urban or suburban areas. The method is simple and easy to apply but criteria points are arbitrarily chosen. Pedestrian facility is taken either continuous or non continuous in the calculation. Degree of discontinuity or continuity has not been assigned proportional points. A little discontinuous and a little continuous facility fall in the same category. Thus intermediate conditions need to be assigned appropriate weightage points. PEDESTRIAN LEVEL OF SERVICE- NICOLE GALLIN Nicole Gallin a BSD Consultant, developed model for assessing the Level of Service (LOS) of pedestrian facilities in Western Australia. The LOS model developed provides a sound basis for the measurement of LOS for pedestrians. Their model not only provides the opportunity to test the LOS provided by a pedestrian route, but also determines which factors contribute to low and high LOS. These factors were classified as design factors (path width, surface quality, obstructions, crossing opportunities), location factors (connectivity, path environment, potential for vehicle conflict) and user factors (pedestrian volume, mix of path users, personal security). Model for assessing pedestrian LOS was developed based on the measurement of these factors influencing LOS. Each factor is assigned a point on the basis of its presence and weights are assigned from the response ratings obtained from various stakeholders. TAN DANDAN et. al. MODEL. TAN Dandan et. al. (2007) studied the methods of assessing pedestrian level of service by analyzing the relationship between the pedestrian s subjective perceptions and the quality of the road physical facilities as well as the traffic flow operation. The model was developed using the 395 real-time observations from 2 urban roadway segment sidewalks in China. The following model was developed: PedLOS = QB 0.003QP QV /W r +.24(P.7P 3 ) Where, QB bicycle traffic during a five-minute period QP pedestrian traffic during a five-minute period QV vehicle traffic during a five-minute period (pcu) P driveway access quantity per meter Wr distance between sidewalk and vehicle lane (m) Following Table-5 may be used as a basis for stratifying the model s numerical result into the rank of pedestrian level of service when it is applied to a particular roadway segment.

7 Table-5: Level of service categories Level of service LOS Value A LOS<2.0 B 2.0 LOS<2.5 C 2.5 LOS<3.0 D 3.0 LOS<3.5 E 3.5 LOS<4.0 F LOS 4.0 They found that the factors which significantly affected the pedestrian LOS were the bicycle volume, the vehicle volume, the pedestrian volume, driveway access frequency and the distance between sidewalk and vehicle lane. TRAFITEC MODEL Jensen Soren Underlien (2007) developed pedestrian satisfaction model using cumulative logit regression of ratings given by pedestrians and variables which relate to the satisfaction ratings. Roadway segments were rated on a six point scale i.e. very dissatisfied, moderately dissatisfied, a little dissatisfied, a little satisfied, moderately satisfied and very satisfied. The model includes type of walking area (asphalt, concrete, bicycle track, paved shoulder, driving lane), type of roadside development or landscape (residential, shopping, mixed, rural fields, rural forest), average motor vehicle speed, motor vehicle volume, pedestrian volume, bicycle and mopeds, buffer area, parked motor vehicles, presence of median, width of walking area, number of driving lanes and presence of trees. The model developed by him is in the form of utility function based on all these variables. General form of his model is:- Logit (p) = {α, WA, AREA, SPEED, MOT, PED, BIKE, BUF, PARK, MED, SB, BL, LANE, TREE} Where: logit (p) = utility function of the cumulative logit model α = intercept parameter of the response level of satisfaction WA = type of walking area AREA = type of roadside development MOT = motor vehicles per hour in both directions SPEED = average motor vehicle speed (kmph) PED = pedestrian per hour on nearest roadside BIKE= bicycle and mopeds per hour in both directions BUF = buffer area width between walking area and drive lane (metres) PARK = parked motor vehicles on road per 00 metres MED = median SB = width of walking area (metres) BL = total width of walking area and nearest walking lane (metres) LANE = drive lane dummy four or more drive lane =, one to three lanes = 0. TREE = tree dummy, one tree or more on road per 50 metres =, otherwise 0. The model provides traffic planners and others the capability to rate roadways with respect to pedestrians satisfaction and may be useful in the process of evaluating existing roads, designing new roads or redesigning existing roads. However the model is very exhaustive i.e. it includes almost every element present in the walkway segments. Furthermore incorporating all these factors and evaluating them is tedious job. Biasness of pedestrian s perception towards satisfaction of particular facility or elements cannot be denied. SOME OTHER METHODS Sarkar proposed a qualitative method to compute pedestrian LOS based on six factors: safety, security, convenience and comfort, continuity, system coherence, and attractiveness (Sarkar, 993). Qualitative attributes of pedestrian environments are described, but not quantified, in Sarkar s work. Since it is a qualitative method, the measurement of each factor is not easy in

8 reality and also most of the factors are linked with each other. Later Khisty developed a quantitative method to determine the pedestrian LOS based on almost same criteria proposed by Sarker (Khisty.C.J, 994). Although Khisty s method provides a quantitative measure of pedestrian LOS on a point scale, the results from this scale is not easy to interpret. Miller et al (Miller et al, 2000) also proposed a scale method for pedestrian LOS assessment. Alternatives were introduced to improve the existing conditions and the proposed model was calibrated by using 3-D visualization. Conjoint technique was used to combine the factors affecting pedestrian LOS (Muraleetharan et al, 2004). Some studies use pedestrian signal delay to define a pedestrian LOS (Joseph et al, 999). SUMMARY AND CONCLUSION The aim of this paper is to present existing pedestrian level of service methods and to compare their theoretical underpinnings and performance. The discussion is restricted only to approaches that have been successfully applied to assess pedestrian level of service. The review undertaken illustrates that, over the years, PLOS methods have been developed in a variety of ways however the analysis of the methods discussed suggests the need for substantial improvements in analysis procedures. The majority of these methods and models have been developed by combining models that have been applied to other choice contexts and, as a result, are not suited to universal applications. Currently available methodologies of assessing service levels for pedestrians are unable to analyze the entire spectrum of the walking experience. The Highway Capacity Manual LOS methodology focuses on ease of movement where as the Sprinkle Consulting (SCI) model merely predicts perceived traffic related safety and comfort. It is a valuable tool in assessing alternative roadside scenarios, but it does not examine actual conditions. Nicole Gallin s model is based on physical description of pedestrian facility and their weightage in PLOS score. Pedestrians perception is not included in the calculation. In Tandan et al model pedestrians perception are based on name of certain parameters only i.e. width, bicycle traffic and obstructions. Their actual dimension and quantity are not considered. Trafitec model though very exhaustive, is not free from pedestrian perception biasness. It is evident from the discussion that no method is universally applicable. We have to go beyond narrowly defined LOS concepts and develop assessment methods that are able to account for the varying spectrum of the walking experience. The assessment methods should not be driven by data that can easily be measured and manipulated quantitatively but should include walking experience of pedestrians and planners. REFERENCES: Burden, Dan, (996), Walkable and Bicycle- Friendly Communities Florida Dept. of Transportation. Dixon, Linda.B. (996), Bicycle and Pedestrian Level-of-Service Performance Measures and Standards for Congestion Management Systems. Transportation Research Record 538, TRB, National Research Council, Washington, D.C., 996, pp. 9. Highway Capacity Manual, National Research Council, Transportation Research Board. Washington, D.C., Jensen Soren Underlien, Pedestrian and bicycle level of service on roadway segments Trafitec, January Joseph S. Millazzo II, Nagui M. Rouphail, Joseph E. Hummer, D. Patrick Allen. (999) Quality of service for interrupted-flow pedestrian facilities in Highway Capacity Manual Transportation Research Record 678, TRB, National Research Council, Washington, D.C., 999, pp

9 Khisty, C. J. (994) Evaluation of pedestrian facilities. Beyond the level-of-service concept Transportation Research Record 438, TRB, National Research Council, Washington, D.C., 994, Landis B.W., Vattikuti V.R., Ottenberg R.M., McLeod D.S., Guttenplan M. (200), Modelling the roadside walking environment: A pedestrian level of service. Transportation Research Record 773, TRB, National Research Council, Washington, D.C., 200, pp Miller, John.S., Jeremy A. Bigelow, and Nicholas J. Garber. (2000) Calibrating pedestrian level-of-service metrics with 3-D visualization. Transportation Research Record 705, TRB, National Research Council, Washington, D.C., 2000, 9 5. Muraleetharan, T., Adachi, T., Uchida, K., Hagiwara, T., Kagaya, S. (2004) A study on evaluation of pedestrian level of service along sidewalks and at crosswalks using conjoint analysis, Journal of Infrastructure Planning, Japan Society of Civil Engineers, Vol.2 No.3, pp Nicole Gallin, Quantifying Pedestrian Friendliness Guidelines for Assessing Pedestrian Level of Service. Walking the 2st Century~20 th to 22nd February 200. Perth,, Western Australia. Pushkarev, B., and Zupan, J.(975). Urban space for pedestrians: A report for the Regional Plan Association. Rep., MIT Press, Cambridge, Mass. Sarkar, S. Determination of Service Levels for Pedestrians, with European Examples. In Transportation Research Record 405, TRB, National Research Council, Washington, D.C., 993. TAN Dandan, WANG Wei, LU Jian, BIAN Yang,(2007), Research on Methods of Assessing Pedestrian Level of Service for Sidewalk. J Transpn Sys Eng & IT, 2007, 7(5), ABOUT THE AUTHORS KAMAL SINGH (singhk@manit.ac.in) is assistant professor in the Department of Civil Engineering at Maulana Azad National Institute of Technology, Bhopal, India. He holds a M.Tech. Degree in Civil Engineering from the same Institute where he is currently working. Presently he is working in the area of pedestrian level of service evaluation. Dr. P.K.JAIN (pkjain0@rediffmail.com) is an associate professor in the Department of Civil Engineering at Maulana Azad National Institute of Technology, Bhopal, India. He holds a Ph.D. Degree in Civil Engineering from IIT Roorkee, India. He has written many research papers in vide areas of civil engineering.