Analysis of the Stair Elevation of Pedestrian Bridges for Pedestrian Safety and Comfort

The increase in community activities and transportation amplifies the necessity for pedestrian facilities. In developing a sustainable city, it is necessary to develop friendly and comfortable pedestrian ways and bridges. A sustainable city development should equipped with several instruments such as ecosystem services-based carrying capacity, integrated inter-city transportation, ecocorridors in the form of gardens and street trees, and others [1, 2]. A city requires comfortable pedestrian pathways and bridges to serve the community in walking and safely crossing roads. Pedestrian bridges serve as facilities for crossing roads, motorways, and railways. However, in reality, many pedestrian bridges in some cities are rarely used. An observation was conducted on a pedestrian bridge near a mall in a city in Indonesia, revealing that only 10 to 20 pedestrians use the bridge to cross the road per day. Interviews were conducted with individuals who chose to disobey the rule and not use the bridge while crossing the highway; their primary reason for avoiding the pedestrian bridge was fatigue, as the stairs were too high, causing exhaustion during ascent.

Well-designed pedestrian bridges improve connectivity and accessibility between different parts of a city. They facilitate smoother and more direct routes for pedestrians, including those with disabilities or mobility challenges. This can significantly enhance the ease of movement across barriers like highways or rivers. These bridges also help reduce congestion at street level. When people choose to walk across a bridge rather than waiting at crosswalks or traffic lights, it can lead to smoother vehicular flow and decreased delays for both pedestrians and drivers. Encouraging walking as a mode of transportation supports sustainability goals by reducing reliance on motor vehicles. Pedestrian bridges promote healthier, environmentally friendly transportation, and help to align urban development with sustainability principles. Some cities, like Copenhagen, are well-known for being very pedestrian- and cyclist-friendly. Tokyo, another example, has excellent pedestrian infrastructure. Many pedestrian bridges throughout the city are designed with comfort and accessibility in mind, featuring lanes for wheelchairs and clear directional signs. The movement of people relies not only on spatial syntactic variables but also on the quality and comfort of pedestrian infrastructure [3].

Numerous stairs in public facilities are not optimally designed in terms of size, making it difficult for users to climb. A study conducted on the design of stairs at a University in Surabaya, Indonesia, found that 32.5% of the stairs did not offer a comfortable size for users [4]. According to the Directorate General of Highways in Indonesia, the recommended specifications include a thread depth of 24-30 cm, a maximum riser height of 15 cm, a minimum lane width of 51 cm for a single path, and a width of 120 cm for two lanes. The maximum slope for public stairs is 30 degrees.

Several pedestrian bridges lack safety and comfort facilities. Desirable attributes of pedestrian bridges encompass adequate lighting, cleanliness of steps and handrails, roofs for protection against rain and heat, and other amenities. The dimensions of pedestrian bridge stairs must ensure user safety during ascent, necessitating a rough surface on the steps to prevent pedestrians from slipping. Causes of falls on staircases include difficulties in seeing steps, poor lighting, high risers, short treads, and slipping off the steps [4]. Inconsistently high risers lead to accidents due to overestimation or underestimation of the height [5].

The energy expended while climbing stairs is proportional to the heavy physical load. In a study at Tirtayasa University, 43% of adolescent respondents expended energy at a heavy level when climbing 2 floors or 8.8 meters of a building [5]. Individuals aged 20 to 35 years exhibit the highest levels of physical ability and strength. Those in optimal physical condition, with an ideal body mass index, demonstrate maximum ability when climbing stairs. However, individuals over 40 years old experience a heavier physical load while ascending stairs. Physical ability can decrease by up to 10% for individuals around 50 years old. Halsey et al. [6] measured heart rate were used to estimate energy expenditure during climbing stairs at speeds chosen by the participants. The height of climbing up and down was 14.05 m. The average energy expenditure for ascending one step per stride was 8.5 kcal/min and ascending two stair steps per stride was 9.2 kcal/min. Experiments were conducted on individuals to measure energy expenditure while climbing stairs. Research used two methods of ascending stairs conducted by Halsey et al. [6], double-step methods need different amounts of work energy from each step method. The study found that the double-step method needs a greater metabolic energy than each step method, energy expenditure for each step method was 1.0-1.3 kcal/hour. The speed of stair climbing differs among age groups. The age group over 60 years old climbs at a slower pace compared to those under 60 years old. Leg extensor power shows a strong correlation with the walking speeds of elderly people on stairs [7]. Yaguchi et al. [8] observed no differences in kinematic and kinetic characteristics in the lower limb between the beginning and end phases of long stair climbing among adolescent participants. The speed of climbing stairs influences the relative aerobic strain and energy efficiency. Mbachu [9] found in his research that higher climbing speed correlates with increased energy efficiency and relative aerobic strain (RAS). High-speed climbing becomes crucial during emergencies using public stairs. The descending speed on stairs is affected by interactions among individuals, individual characteristics, and flow units [10]. Extensor power represents the walking speed of elderly people, it shows a strong correlation to people climbing stairs. The inclination of the stairs has a linear relationship with climbing speeds on stairs [7]. In a study of stair climbing speeds, university students demonstrated a maximum ability of 122 steps per minute, sustaining this pace for 2-6 minutes [11]. Gender affects the speed of descending stairs, with male groups descending faster than female groups [12].

The design of public facility stairs that disregard energy expenditure in climbing often deters many people from using them. In addition to demanding significant energy, stairs also pose a potential risk of injury, especially for adult and elderly age groups if they are not used carefully. However, despite these drawbacks, the use of stairs also offers health benefits. Regularly ascending and descending stairs can enhance the body's metabolism and guard against metabolic syndrome [13-15]. Metabolic syndrome involves the stabilization of various components related to blood glucose levels, LDL, HDL, total cholesterol, blood pressure, lipid fractions, and abdominal obesity. Individuals who frequently engage in stair climbing as part of their daily activities have shown improvements in cognitive abilities, reporting increased energy, reduced irritability, and decreased fatigue [16]. Physical activity, including walking in a comfortable environment, positively affects both physical health, as measured by heart rate and blood pressure, and mental health, as assessed by the Indonesian versions of the Profile of Mood States (POMS) and State Trait Anxiety Inventory (STAI) by Pratiwi et al. [17]. By providing safe and comfortable pedestrian bridges, the quality of life for city residents can be improved, creating a more welcoming and comfortable environment for everyone. The use of non-motorized transportation, such as walking and using pedestrian bridges, supports the principles of sustainable and environmentally friendly transportation. This aligns with the global goal of reducing emissions and dependence on private vehicles by encouraging walking and the use of mass transit.

The study aims to analyze the pedestrian workload while using pedestrian stairs. It investigates how physiological loads during stair climbing relate to pedestrian age, seeking to determine the age limit at which individuals feel comfortable and safe when ascending the stairs on the current bridge dimensions. The study models the physical load experienced while climbing pedestrian bridge stairs by age and examines how the slope of the stairs can be adjusted to promote health, and safety, and increase user preference.

Physical work capacity refers to a worker’s potential for energy output, primarily dependent on the energy available in the form of food and oxygen, which collectively sum up the energy provided by both oxygen-dependent and oxygen-independent processes.

Field observations involve direct measurement of the working and resting pulse of the subject using oximeters. The upper limit is the individual’s predicted maximum volume of oxygen uptake in litre per minute, calculated from a calibration procedure utilizing a predicted maximum heart rate given by [19]:

$H R(\max )=200-(0.65) * a g e$     (2)

Participant characteristics and the maximum heart rate are presented in Table 1.

Table 1. Subject characteristics and their heart rate upper limit

The late adolescence group is the 1st to 30th subject, the early adulthood group is the 31st to 60th subject, and the late adulthood group is the 61st to 90th subject.

3.1 Working energy

The working energy is classified based on the ratio of energy consumption (working pulse) to the maximum capacity of subjects, expressed as a percentage of cardiovascular load (%CVL). Table 2 presents subject’s cardiovascular load during climbing stairs and rest periods. Orange cells in the table represent subjects expending energy at high levels when climbing stairs, while yellow cells indicate subjects expending energy at a moderate level.

Table 2. Subject pulse (beats/minute) during climbing stairs and recovery times

According to Table 2, the subjects' pulse rates before climbing stairs ranged from 70 to 100 beats per minute, while the working pulse measured shortly after climbing the stairs ranged between 92 and 135 beats per minute. Within the early adulthood group, 3 subjects, or 10% of the group, expended energy at heavy aerobic levels with a %CVL of more than 50%, while 14 subjects making up 46.67%, expended energy at a moderate aerobic level. In the late adulthood group, a total of 13 people, or 43.33% of subjects, expended energy at heavy aerobic levels, and 15 individuals, or 50%, expended moderate energy while climbing the pedestrian bridge stairs.

Bridgers [19] proposed a method for determining excessive work intensity. The heart rate is measured between 30 seconds and 1 minute after the cessation of work and again between 2.5 and 3 minutes. The first reading should not exceed 110 beats per minute, and the second reading should be at least 20 beats per minute lower. An initial reading surpassing 110 beats per minute suggests excessively arduous work for the individual. If the first reading is below 110 beats per minute and the second reading is not at least 20 beats per minute lower, it implies that the work–rest cycle contains insufficient rest. Climbing bridge stairs led to an increase in pulse exceeding 110 beats per minute for some subjects, indicating excessive work intensity. The high work intensity deters some pedestrians from using pedestrian bridges.

The physical ability of subjects is influenced by various factors such as age, exercise habits, food intake, and gender, among others. With differing physical capacities, the physical load during stair climbing is estimated based on percentage of cardiovascular load (%CVL). Percentage of CVL is a helpful measure in assessing effort and intensity [20].

The percentage of cardiovascular load is an objective means of assessing estimated energy consumption (HR_work) against the maximum capacity of subjects. It indicates the percentage of the energy used by an individual in relation to their available capacity. This energy estimate is particularly suitable for work involving a significant physical contribution and having a lower influence on mental factors. Percentage of CVL serves as an objective assessment because it considers everyone’s maximum ability and reflects relative intensity more accurately. The slope of the stairs in this research is well-suited for the adolescent age group (17-25 years old) and some within the early adulthood group (25-35 years old). However, the slope of these stairs is unsuitable for individuals in the late adulthood age group, especially those above 35 years, as 43.33% of subjects in this age range expend energy at a heavy level when climbing stairs.

3.2 Data processing

In planning a pedestrian bridge designed to serve community members ranging from children to the elderly, it is crucial to understand the physical load experienced by individuals of various ages while climbing stairs. To this end, a linear regression formula was developed to quantify the energy expended during stair ascent.

Data on the subjects’ age and their corresponding %CVL were collected and plotted on a scatter diagram. This plot revealed a strong linear correlation between %CVL and subject age, indicating that as age increases, so does the cardiovascular load during stair climbing. Figure 1 illustrates the plotted data, visually representing the relationship between %CVL and subject age.

1.png

Figure 1. Scatter diagram of relative cardiovascular load (%CVL) and subject age

Based on the scatter diagram, there appears to be a positive relationship (or positive correlation) between the subjects' age and the subjects' %CVL. As subjects' age increases, their %CVL also tends to increase.

Formulating the linear equation for %CVL during stair climbing with a 27-degree slope:

$y=0.999 x+8.733$     (3)

where, y = subject’s CVL(%), x = age (years).

A linear regression model was generated using Excel from Office 2019. The multiple R, which is the correlation coefficient, resulted in a strong correlation within the model with a value of 0.795.

Based on the energy formula related to age, the slope of the pedestrian bridge stairs commonly found in the research is only suitable for individuals up to 41 years old. Beyond this age, a person is likely to experience a cardiovascular load above 50% or the high load category.