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Quantifying performance of sheltered link-way facility in Singapore using human-centric indicators Quantifying performance of sheltered link-way facility in Singapore using human-centric indicators
Sun, S.; Zhou, Q.; Lal, S.; Xu, H.; Goh, K.; Wong, Y. D.
2021-05-04 00:00:00
INTERNATIONAL JOURNAL OF URBAN SUSTAINABLE DEVELOPMENT 2021, VOL. 13, NO. 2, 187–198 https://doi.org/10.1080/19463138.2020.1858422 ARTICLE Quantifying performance of sheltered link-way facility in Singapore using human-centric indicators a a a b c a S. Sun , Q. Zhou , S. Lal , H. Xu , K. Goh and Y. D. Wong a b School of Civil and Environmental Engineering, Nanyang Technological University, Singapore; School of Social Sciences, Nanyang Technological University, Singapore; Land Transport Authority, Singapore ABSTRACT ARTICLE HISTORY Received 6 February 2019 Pedestrian link-ways are important street facility for first-/last-mile mobility. This Accepted 28 November 2020 study compared pedestrians’ walking experiences on sheltered/unsheltered link- ways by collecting their perceived walking time/distance. It is found that, first, KEYWORDS pedestrians (51 along sheltered and 49 along unsheltered link-ways) generally walk Infrastructure improvement; at a faster pace along unsheltered link-ways as compared to sheltered link-way. cognitive bias; walking time; Second, participants are found to more likely over-perceive walking times and walking distance; level of distances (with odds of three to one) along unsheltered link-way than sheltered link- service way, and with more extreme deviations on unsheltered link-ways. Third, sheltered link-ways accrued better Level of Service (LOS) ratings on factors such as weather protection, distance, accessibility/user-friendliness, comfort, safety and level of crowdedness. The study demonstrates value-add application of cognitive bias approach for examining the walking experience, and provides human-centric indica- tors to justify the provision of shelters to the link-way for the benefits of pedestrian users. 1. Introduction together with bus/rail public transport, are popular urban transport modes nowadays, with benefits in trans- The prevalence of car-reliance and labour-saving devices port mobility, energy conservation, and environmental has increasingly changed urban lifestyle. In the large friendliness. In the year 2017, average daily buses rides in literature of urban design, physical activities such as Singapore stood at 3.9 million, for a resident population walking and cycling have been well encouraged as of 5.5 million, within a land area of 720 km . A stated a push to good health. A major infrastructural improve- intention of the Authority is to have 75% of all peak hour ment to encourage and promote walking is providing journeys made on public transport, by 2030 (LTA 2013). shelter along pedestrian link-ways. In Singapore, the A variety of indicators has been applied to quantify Land Transport Authority (LTA) has been building shel- impacts of commuters’ travelling experience on their ters over existing pedestrian link-ways to provide shel- subsequent route choice. The likelihood of selecting tered connectivity between transport nodes and a given route from among a set of alternative routes is schools, health care facilities, residential developments found to be much influenced by the perceived travel- and public amenities within a 400 m radius of all Mass ling time/distance as well as the preference of indivi- Rapid Transit (MRT) stations and within a 200 m radius of dual travellers (Connors and Sumalee 2009). The all LRT stations and bus interchanges. Sheltered link- walking journey time/distance would be based on ways are also being provided to connect existing bus pedestrians’ perceived values and prior experience. It shelters with high usage to trip generating hubs within is rationalised that providing shelters to the link-ways, a 200 m radius of these bus shelters. Active mobility such for protection from inclement weather conditions as walking, and riding Active Mobility Devices (AMDs), CONTACT Y. D. Wong cydwong@ntu.edu.sg School of Civil and Environmental Engineering, Nanyang Technological University, Singapore © 2020 Informa UK Limited, trading as Taylor & Francis Group 188 S. SUN ET AL. such as rain and hot sunshine, can favourably influ - respondents (total number is 126) complained that ence a pedestrian’s perception of the walking journey. inclement weather prevent them from walking more Such cognitive bias in the pedestrians’ perceptions often. In addition, 56% of respondents were moti- provides a rational basis to examine the efficacy of vated to walk when weather is good. Mostly, in areas scheme implementation. that have extreme weather such as high precipitation This paper aims to study the cognitive bias on infra- and temperature, reasonable weather protection structural improvement by evaluating and comparing plays a fundamental role that can encourage people pedestrians’ perception of walking time/distance and to walk. To improve walking environment for pedes- level of service along sheltered versus unsheltered link- trians, Alfonzo (2005) proposed weather buffers (e.g. ways adjoining MRT stations in Singapore. Walking arcades, canopies) for urban designers who intend to time and distance perceived by experimental subjects offer protections. Herein, providing sufficient weather are compared against measured values, based on protection for travellers (both pedestrians and AMD a journey along 400-m stretches of the link-ways. An riders) will improve their perceived LOS, and thus indicator by way of an Index of Difference between encourage more active mobility travel. Perceived and Measured time/distance (IDPM ) is Apart from weather protection, a plethora of vari- t;d defined to quantify the degree of deviation in the ables lies behind a pedestrian’s decision to walk. subjects’ perceived walking time and distance. Therein, physical exercise activities, demographics, A number of factors, such as crowdedness, weather safety, residential characteristics and familiarity have protection, comfort and accessibility are rated by the been tested on how they affect walking behaviour (Li subjects on the walking environment to obtain the et al. 2005; Loukaitou-Sideris 2006; Forsyth et al. 2007, users’ feelings about the link-way facility. Literature 2008; Kerr et al. 2012; Longo et al. 2015; Perchoux findings are first reviewed in the following Section 2, et al. 2017). Although correlation between infrastruc- followed by methodology in Section 3. The results and ture and traveller behaviour has been identified, the discussion are then presented in Section 4, and Section influence of each factor does not affect equally on the 5 concludes the paper. pedestrians, nor can the pedestrians accurately per- ceive those identified factors. The built environment and its potential impacts on 2. Literature review promoting sustainable behavioural patterns of indivi- duals need to be identified based on detailed knowl- 2.1. Perceived level of service edge of people’s preferences and willingness to The perceived level of service (LOS) of a walking facil- comply (Brand 2013; Goel and Sivam 2015). To encou- ity can be quantified using a basket of qualitative rage sustainable travelling practice (i.e. active mobi- factors (e.g. convenience, comfort safety, security, lity) in urban areas is to learn the effective ways to economy) as reflecting the pedestrians’ perception design infrastructure that can easily nudge commu- of the walking environment (Henson 2000). Weather ters to adapt as part of their travelling patterns. In protection is categorised as an important comfort Singapore, most pedestrian link-ways were previously factor that contributes to the walking experience. open pathways. They have now been retrofitted with Sarkar (2003) defined adverse weather protection as shelters within 400 metres of MRT stations (Lee 2014). the capability of protecting pedestrians from rain, According to Ovstedal and Ryeng (2002), the connec- snow, sleet, and extremely high and low tempera- tion between the different elements of weather con- tures. In Singapore, infrastructural factors were rated ditions and the comfort feeling was indirect while the by pedestrians in a perception survey conducted by direct influence is associated with how the pedes- Koh and Wong (2013). Weather protection was ranked trians assess the weather conditions. In the present first with an average score of 3.5 (on a 4-point scale study, the efficacy (e.g. perceived reduction in walking spanning 1: Not important to 4: Very important) distance or time, perceived higher satisfaction levels) among 810 pedestrian subjects. Link-ways with/with- of providing shelter shall be evaluated, which can be out shelters provide different weather conditions (e.g. studied by comparing pedestrians’ perceptions of the sun protection, rain protection) for pedestrians. infrastructure and operating conditions when walking Similarly, in the tropical environment of Malaysia, along sheltered link-ways versus unsheltered link- Ariffin and Zahari (2013) found that 32% of ways, for the case of Singapore. INTERNATIONAL JOURNAL OF URBAN SUSTAINABLE DEVELOPMENT 189 2.2. Cognitive bias selected stretch. Only at the end of the journey, the participants were requested to make a judgement on In the realm of psychology, Watson (1919) introduced their perception of time, distance and general level of a hypothesis into psychological theory which states satisfaction. that ‘given the stimulus, psychology can predict what Various technical methods to quantify travellers’ the response will be; or, on the other hand, given the perception have been applied to study the efficacy of response, it can specify the nature of the effective infrastructural improvement. Stone and McBeath stimulus’. With regard to perception, stimuli can be (2010) applied spatial distance estimation on 12 sub- visual (sight), auditory (sound), tactile (touch), olfactory jects (6 males and 6 females) and found that gender (smell), or gustatory (taste). According to Berlyne difference can influence distance estimation. González (1960), apart from stimulus inputs, level of attention et al. (2015) used perception error rate of time to or awareness would also elicit different subjects’ measure distorted perception and found that error responses. Specifically, Nutter and Esker (2006) pro- rate decreases as real travel time increases. Herein, posed ‘just noticeable difference threshold’ measure- perception deviations of walking time and distance ment to quantify the difference between the actual exist, and are influenced by operating conditions, change in a physical stimulus and the perceived socio-demographic and infrastructural factors. For this change. Similarly, cognitive bias is defined as study, the deviations perceived in walking distance or a systematic pattern of deviation from norm or ration- time as well as perceived LOS were examined by com- ality in judgement (Buss 2005). It is claimed that indivi- paring the perceptions of the subjects when walking duals could create their own ‘subjective social reality’ along sheltered link-ways versus unsheltered link-ways. from their perception of the input factors. In transport study, cognitive bias has been applied to understand how the elements of the travelling envir- 3. Methodology onment affect travellers’ general comfort and satisfac- tion. For instance, Von Sturmer et al. (1968) carried out Cognitive bias of pedestrians’ perceived time, distance an experiment among 36 subjects and found that, the and LOS can be investigated by arranging a walking higher the level of distraction, the less time a subject journey with and without some factors whose influ - will perceive. Another study by Chowdhury et al. (2015) ence on perception is to be assessed. In this study, on- found that commuters perceive reduction of travel site survey was carried out to examine the difference in time and cost as influenced by certain comfort ame- perception of time, distance and LOS along sheltered nities (such as shelter, information and lighting) at bus versus unsheltered link-ways. The study was approved interchange. By conducting a comparison of perceived by the Institutional Review Board at Nanyang distance at interesting versus mundane places, Technological University, Singapore. Two sites each Crompton and Brown (2006) found that small-scale (four in total), adjoining MRT stations in Singapore, places without cars may seem much larger than were selected for conducting the survey (Figure 1). expected although the actual distance was measured An illustration of the observed activities on both as being equal. Therefore, it is important to pay atten- sheltered and unsheltered link-ways are shown in tion to how travelling environment influences pedes- Figure 2. For the survey, participants were randomly trians’ subconscious perception, and not only how the selected during afternoon (14:00 to 16:30 hrs) and travelling environment is built. Moreover, the quantifi - evening periods (16:30 to 19:30 hrs). They were asked cation of the degree of perception deviation needs to to walk along a 400-m stretch, and an interviewer be as comprehensive as possible. Both perception of trailed along with each participant till the end point travel time/distance and perceived LOS should be con- (so as to prevent interrupting their walking pace and sidered at the same time. perception of time/distance), which was then followed In fact, different cognitive processes underlie two by an interview. A timer was started at the onset of paradigms, when participants are aware they are being each journey to record the exact time that the subject timed (prospective) and when they are unaware they are took to walk the defined stretch. Participants were not being timed (retrospective) (Zakay and Block). In the informed in advance of the actual time/distance being present study, participants were unclear of the actual paced. Upon reaching the end point, the participants time/distance until they had completed walking the were asked to report their perceived travel time (within 190 S. SUN ET AL. Figure 1. Journey survey site locations (Google, n.d.). Figure 2. Field survey of participants on sheltered (above) and unsheltered (below) link-ways. Figure 3. On-site setup of the heat stress tracker. INTERNATIONAL JOURNAL OF URBAN SUSTAINABLE DEVELOPMENT 191 Table 1. Distribution of participants. Pioneer MRT station Lakeside MRT station Afternoon period (14:00 to Evening period (16:30 to Afternoon period (14:00 to Evening period (16:30 to Link-way 16:30 hrs) 19:30 hrs) 16:30 hrs) 19:30 hrs) Sheltered 12 15 11 13 Unsheltered 12 12 12 13 Total 100 Table 2. Summary statistics of walking times and distances (n = 100). Perceived time Measured time Perceived distance Sheltered Unsheltered Sheltered Unsheltered Sheltered Unsheltered Mean 386.5 s 442.2 s 344.7 s 337.0 s 384.9 m 500.6 m Median 330.0 s 390.0 s 343.0 s 330.0 s 350.0 m 500.0 m Minimum 180.0 s 180.0 s 240.0 s 272.0 s 100.0 m 100.0 m Maximum 900.0 s 900.0 s 468.0 s 466.0 s 1000.0 m 1040.0 m 10-second resolution) and distance for the journey. walking time as measured by the interviewers. The Each participant was provided with an honorarium of degrees of over-estimation are more severe for S$10 (≈US$7). unsheltered link-ways than for sheltered link-ways. In Weather condition monitoring was done in parallel another word, the cognitive bias is observed to be to the walking survey along sheltered and unsheltered more severe on unsheltered link-ways. link-ways by using a Heat stress tracker (Figure 3). The The results for paired-sample t-test of the means tracker was set 1.2-m high on the side of the link-way to between perceived and measured walking times and minimise the obstructive effects on link-way users. walking distances are shown in Table 3. Paired sample In total, 100 participants consented to participate in t-tests show that there is significant difference in the the study. More than 10 subjects at each designed mean values of time and distance for unsheltered sce- section were interviewed. The distribution of all parti- nario, with the difference being more distinctive for cipants are recorded in Table 1. The results are dis- walking time. In contrast, there is no significant differ - cussed in the following section. ence in the mean values for sheltered scenario. The findings also suggest that walking time in unsheltered scenario is a more discriminatory indicator in pedes- 4. Results and discussions trians’ cognitive bias on the pace of mobility along link- ways. For further research, one can rely more on time 4.1. Results perception since people can make a more reliable The perceived and measured values for walking time judgement of time rather than distance. and distance are recorded when each participant Walking speed is computed from the actual time completed the 400-m journey. The summary statistics taken by each participant as measured by the inter- are shown in Table 2. The mean values of the per- viewer. The cumulative distribution is shown in Figure ceived walking time are greater than those of actual 4. The (average ± SD; median) walking speeds are: Table 3. Two-tailed paired-sample t-test results for perceived and measured walking times and distances. P [perceived > measured], 2-tailed Parameter Link-way Perceived mean value Measured mean value paired-sample t-test Walking time Unsheltered 442.2 s 337.0 s Significant, p = 0.000 *** Sheltered 386.5 s 344.7 s Not significant, p = 0.104 Walking distance Unsheltered 500.6 m 400 m Significant, p = 0.002 ** Sheltered 384.9 m 400 m Not significant, p = 0.602 Note: **: p <.01; ***: p < .001 192 S. SUN ET AL. Figure 4. Cumulative percentage of walking speeds in sheltered and unsheltered link-ways. (1.19 ±0.02; 1.17) m/s for sheltered link-ways, (IDPM = 0%). Whereas there are higher cases of t;d (1.21 ±0.02; 1.21) m/s for unsheltered link-ways, and under-estimation of walking time and distance along (1.20 ±0.02; 1.19) m/s overall. It is seen that pedestrians sheltered linkways (left half of plot), the odds are generally walk at a faster pace along unsheltered link- about three to one in favour of over-estimation for ways as compared to sheltered link-ways, yet they unsheltered link-ways. Hence, it can be seen that perceived as walking longer and farther in unsheltered walking time and distance, as perceived by the pedes- than sheltered linkways. trians, are twice and thrice as likely to be over- per- ceived (than under- perceived) when walking in unsheltered conditions. 4.2 Discussions Based on overall results of mean IDPM value, t;d males had higher mean IDPM values than t;d In order to evaluate the degree of cognitive bias between the perceived and measured values, a dimensionless indicator by way of Index of Difference between Perceived and Measured time/dis- tance IDPM is defined to quantify the difference t;d between perceived and measured values of the walk- ing time and distance, as shown in Equation (1). IDPM > 0 when there is over-estimation, and vice- t;d versa. The IDPM indicator is useful for counting the t;d frequency of over-estimation and under-estimation. perceived measured i i IDPM ¼ � 100% (1) t;d measured where i is participant number; IDPM for walking time, andIDPM for walking distance. IDPM values for walking time and distance are t;d calculated for each participant for which the points are plotted as shown in Figure 5, segmented by shel- tered and unsheltered link-ways. The IDPM points t;d are scattered above (over-estimation) and below Figure 5. IDPM for sheltered and unsheltered link-ways (n = 100). (under-estimation) the neutral horizontal line t;d INTERNATIONAL JOURNAL OF URBAN SUSTAINABLE DEVELOPMENT 193 Figure 6. Mean IDPM by gender. t;d Figure 7. Mean IDPM by age. females, especially for walking time at unsheltered appears males have greater degrees of over- link-ways (Figure 6). The results for walking dis- estimation than females. tance are mixed, with positive mean IDPM values The estimation of walking time across the six age for males and mixed values for females. Overall, it bands is rather mixed (Figure 7). The limitations of Table 4. Summary statistics of IDPM in afternoon and evening periods. t;d Afternoon period (14:00 to 16:30hrs) Evening period (17:00 to 19:30hrs) Category IDPM (%) IDPM (%) IDPM (%) IDPM (%) t d t d Mean 23.4 14.1 21.9 7.1 Median 10.0 12.5 0.3 0.0 Minimum −50.7 −75 −51.1 −75 Maximum 163.2 160 230.9 125 194 S. SUN ET AL. Figure 8. Relative humidity and temperature variations. a small sample size for multi-class classification would period (Table 4) despite the greater utility of shelter in make the distribution indicative only. It appears that the afternoon than in the evening. as pedestrians get older, the degree of over- Temporal temperature was lower, and relative estimation seems to get more severe. humidity was higher, along sheltered link-ways, The mean and median IDPM values during the relative to unsheltered link-ways (Figure 8). Also, t;d afternoon period are higher than those for evening fluctuations of temperature and relative humidity Figure 9. Comparison of satisfaction score of affecting factors between sheltered and unsheltered link-ways. INTERNATIONAL JOURNAL OF URBAN SUSTAINABLE DEVELOPMENT 195 were less in sheltered link-ways as compared to stretch of link-way, 51 along sheltered link-ways, and unsheltered link-ways. This shows that while pro- 49 along unsheltered link-ways. viding the shelter reduces ambient temperature, it A strong tendency was found for subjects to has the dis-benefit of elevating the relative humid- over-perceive their journey times and distances ity. The greenery (i.e. grass or trees) along both when walking along the link-ways. This tendency sheltered and unsheltered link-ways is quite similar, is much greater, at odds of three to one, for sub- therefore, it is not difficult to envisage that the jects walking along unsheltered link-ways. The difference in relative humidity and temperature is degree of over-perception was also more extreme due to the provision of the shelter which might along unsheltered link-ways. This shows that the prevent evaporation beneath the shelter. utility of providing shelters which can make the journey appear not as far as when walking in the open. 4.3. Pedestrians’ satisfaction with the provision Meanwhile, more favourable ratings in the LOS of shelters were accorded to the sheltered link-ways in such As shown in Figure 9, under-sheltered link-ways, environmental factors as weather protection, dis- survey participants rated relatively higher satisfac- tance, accessibility/user-friendliness, comfort, safety tion score for factors like weather protection, dis- and level of crowdedness. On the other hand, there tance, accessibility/user-friendliness, comfort, was a better score on security (fear of theft or safety. In contrast, when along unsheltered link- vandalism involving bicycles) along the unshel- ways, participants rated higher satisfaction score tered link-ways. Again, there are strong merits in for security (fear of theft or vandalism involving the provision of shelters towards enhancing the bicycles). For factors like crowdedness, ancillary travelling environment for the pedestrians. facilities, cleanliness and security (in particular This study demonstrates the value-add applica- bicycle theft), there is no distinctive difference in tions of human-centric indicators to justify the pro- the satisfaction scores for sheltered and unshel- vision of shelters to the link-way for the benefits of tered link-ways. The positive users’ experience in pedestrians. Cognitive bias in pedestrians’ percep- walking under sheltered link-ways makes their per- tion of walk time is found to be a discriminant ceived of time and distance closer to the true indicator. Likewise, users’ ratings of the operating values; whereas the relatively less positive users’ environment show that the sheltered link-ways are experience in walking under un-sheltered link- more conducive mobility environment than open ways elongated their perception of time and dis- link-ways. tance (Table 2). On the premise that pedestrians would walk at a constant speed, the perception of 6. Implications and outlook greater walking time is translated into longer dis- tance for walking under-unsheltered link-ways. The importance of walking as a stimulation of Therefore, the perception of time and distance good health and public transport has been well can be biased by the environment – the less com- established in the public health and transport lit- fortable journey seems to be longer than under the erature. Infrastructural improvements shall need to more comfortable journey. The actual survey ques- be examined carefully to identify efficient schemes tions are attached in the Appendix. to encourage active mobility in the urban areas (Joh et al. 2012). The findings of user-centric indi- cators show very positive values in enhancing the 5. Conclusions quality needs of the pedestrian, by way of provid- This study reports empirical findings of pedestrians’ ing shelters to the pedestrian link-ways. Currently perceived values in response to provision of a shelter in Singapore, sheltered link-ways are provided if along the pedestrian link-way. The performance of major activity centres such as schools, health care link-way shelter was examined by way of cognitive facilities are within 200 m to 400 m radius of bias on journey time and distance perceptions, as well transport nodes. By 2030, eight in 10 homes as Level-of-Service (LOS) ratings. For the experiment, would be within 10-minute walk from a train sta- a sample of 100 subjects walked along a 400-m tion (LTA 2013). 196 S. SUN ET AL. Positive findings from this study could provide the References impetus for the Authority to explore extending the Agrawal AW, Schimek P. 2007. Extent and correlates of walking coverage of covered link-ways given the prevalence of in the USA. 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