Investigating the impact of street width-to-height ratios on stress recovery

Abstract

The rapid urbanization has heightened psychological pressure on pedestrians, leading to a rise in mental health disorders. Given the significance of street spaces as crucial public domains in daily life, they offer a potential strategy for reducing stress and promoting general health and wellness. This study aimed to investigate effects of street width-to-height ratio (W/H) on stress recovery, using virtual reality technology to create five street scenes with distinct W/H ratios: 0.5, 1.0, 1.5, 2.0 and 4.0. The investigation encompassed psychological and physiological indicators of 48 participants. The findings demonstrated that streets with W/H ratios ranging from 1.0 to 2.0 were perceived as more conducive to stress recovery. Subjectively, such streets received elevated Restorative Components Scale scores, ranging from 0.89 to 1.03. Moreover, physiological indicators revealed a significant reduction in pulse pressure (0.07–0.86 mm Hg). The lower LF/HF (0.75–1.0) indicates a dominance of the parasympathetic nervous system (PNS). This is further supported by a higher pNN50 (16.72–16.97%) associated with PNS activation and a longer RR (the time between two consecutive R-peaks, 768.60–773.10 ms), reflecting a significant reduction in physiological stress. Extreme function fitting analysis demonstrated that W/H = 1.25 exhibited the most substantial stress recovery effect amongst the various street configurations tested.

Keywords

Street width-to-height ratio Stress recovery Heart rate variability Blood pressure Restorative components scale

Introduction

The rapid advancement of globalization and urbanization has resulted in the growing presence of traffic noise, environmental pollution and psychological stress, which are key factors driving the rise in mental health disorders.^1,2 A substantial body of research highlights the beneficial impact of natural environments on stress recovery and overall well-being.^3–5 Nonetheless, the scarcity of time and opportunities to connect with nature renders it inadequate to depend exclusively on natural environments for improving health. Consequently, researchers have shifted their focus to investigating the restorative effects provided by everyday urban environments. Streets, as prominent urban elements, extend to every part of the city, comprising 25–35% of the total developed area. As the most frequently encountered daily landscape for urban residents, streets offer minimal opportunities to select favourable routes and avoid unfavourable ones.⁶ Thus, the resilience of streets is crucial for the psychophysiological well-being of inhabitants. Integrating existing knowledge of restorative environments into streetscape design presents a viable approach to creating spaces that align with public preferences and alleviate mental stress. Regrettably, research on the restorative potential of urban streetscapes remains relatively sparse. While much of the focus has been on the role of street vegetation,^7–9 other aspects, such as building complexity on either side of the street,¹⁰ traffic and historical features,¹¹ street-level businesses and overall aesthetics, have typically been explored in isolation.¹²

Street width-to-height ratio (W/H), a fundamental element of street spatial scale, has garnered significant consideration in studies related to the street wind environment, thermal environment and air quality.^13–15 However, its influence on pedestrian perception experience and stress recovery has received limited exploration. Sitte¹⁶ proposed that W/H ratios between 1.0 and 2.0 correspond to an appropriate spatial scale, providing a more comfortable experience for individuals. When the W/H is below 1.0, the increased sense of enclosure leads to feelings of depression. Conversely, when the W/H is above 2.0, the open space feels too dispersed.¹⁶ Herzog¹⁷ observed that street spaces with moderate W/H ratios were more popular compared to those with excessively large or small W/H ratios. Stamps¹⁸ emphasized the significance of street W/H on the sense of enclosure and highlighted that the optimal building height might rely on whether the street view is blocked by adjacent buildings. Alkhresheh¹⁹ considered safety and comfort as preference indicators and demonstrated an inverted U-shaped relationship between these factors and street W/H. Lindal and Hartig¹⁰ proposed that when the street width was fixed at 6 m, an increase in building height from 5.0 to 11.6 m negatively affected subjective restoration. Similarly, Yao et al²⁰ found that the most favourable pedestrian space perception experience was found in underground shopping streets measuring 6–7 m in width and 4–5 m in height. However, the impact of W/H on urban streets remains insufficiently explored. The optimal W/H for pedestrian stress recovery remains unclear. The aforementioned studies primarily focused on subjective perception, utilizing methods such as the Likert scale and semantic analysis to gather people's evaluations, which are inherently subjective. As physiological measurement technology continues to advance, a growing number of researchers are exploring the impact of street environments on psychophysiology by combining physiological signals.^21,22 For instance, Yu et al.²³ found that poor street environments increase systolic blood pressure (SBP) and physiological stress. De Brito et al.²⁴ demonstrated that uncomfortable street environments activate the sympathetic nervous system (SNS), leading to increased neural stress, as indicated by heart rate variability (HRV). Physiological indices such as blood pressure (BP) and HRV are effective measures for evaluating the quality of street environments. Additionally, the development of virtual reality (VR) technology has shown significant advantages in reducing experimental costs and improving efficiency, while also demonstrating high consistency between VR and real environments. Zhang et al.²⁵ explored the similarities and differences in individuals’ perceptions of street features using VR and eye-tracking technology. Liu et al.²⁶ compared the impact of different street greenery on stress recovery amongst youngers, utilizing VR, Restorative Components Scale (RCS), BP and HRV. VR has been proven effective in recreating real street environments. In general, most existing studies provide a suitable range for street W/H but do not specify the optimal values for stress recovery. These studies mainly emphasize the significant impact of building height on restorative effects based on subjective evaluations,¹⁰ without quantitative analysis incorporating objective physiological indicators. The combination of VR and comprehensive psychophysiological measurements has become an important paradigm for studying urban environment perception. Therefore, it is essential to utilize VR technology to explore the optimal W/H conducive to pedestrian stress recovery by integrating subjective evaluations with objective multi-parameter physiological indicators.

In this study, effects of street W/H on stress recovery were thoroughly investigated. To achieve this, five distinct street scenes with varying W/H ratios of 0.5, 1.0, 1.5, 2.0 and 4.0 were designed and created using VR technology for experimental testing. Stress recovery was assessed both subjectively, through the RCS and objectively, by comparing BP parameters (SBP, diastolic blood pressure (DBP), pulse blood pressure (PBP)) and HRV parameters (LF/HF, pNN50, RR). The primary goal was to determine the most conducive street W/H for stress recovery, based on a comprehensive analysis of psychophysiological indicators. These findings aim to provide valuable recommendations for creating high-quality street environments that foster stress recovery and overall well-being.

Materials and methods

Different from Beijing, Shanghai and other modern metropolises, the main urban block of Qingdao features a large number of traditional streets. These streets originated from the German colonial period and are predominantly lined with traditional buildings 2–3 storeys high, possessing rich historical value. Demolition and construction are strictly regulated. Compared to modern streets, the environmental characteristics of traditional streets could help relieve mental stress in pedestrians and improve public health; this finding could provide valuable insights for street design and offer strong support for the preservation of traditional streets. Therefore, the traditional urban block of Qingdao has been selected as the research area.

Participants

To avoid the confounding effects of individual factors such as age and region, relatively strict selection criteria were applied to participants. In June 2022, participants were recruited from a school, and the selection criteria were as follows: (1) participants were required to be 18–35 years old. The youth population experiences significant psychophysiological stress due to prolonged exposure to high-pressure work and life environments. While most research focuses on the elderly, exploring how passive interventions in the daily environment can alleviate stress in young people is meaningful. Therefore, this study's sample population was set to include only young individuals. (2) Participants must have no history of mental disorders or cardiovascular diseases. (3) Participants must have lived in Qingdao since childhood or in Qingdao's traditional blocks for more than 3 years and be familiar with traditional streets. Familiarity with streets can affect perception and experience, and local people are more likely to appreciate the unique characteristics of traditional streets influenced by local culture and social habits. G*Power was utilized to calculate the sample size, with power analysis employed to ensure a high level of statistical power while reducing the risk of errors. The significance level, α, represents the likelihood of a false positive error, while β signifies the probability of a false negative error, and (1 − β) indicates the ability to detect a true effect.²⁷ This study employed a within-subject design and analysis of variance (ANOVA), assuming (1 − β) = 0.8 and α = 0.05. Based on Cohen's criteria, a medium effect size (0.25) was selected,²⁸ resulting in a minimum required 16 participants.²⁹ In total, 48 participants were recruited, including 22 males and 26 females, meeting the sample size requirement. The participants’ demographic information is presented in Table 1. Due to recruitment conditions and sample availability, male participants were primarily lower-year undergraduates, while female participants included both undergraduates and some graduate students, leading to age range discrepancies between genders. However, considering that the age range of 18–27 is commonly used in related studies and that university students generally exhibit a homogeneous lifestyle,^30–33 this study does not aim to investigate gender differences in stress recovery. Therefore, the 48 participants can be regarded as a single group. Additionally, similar studies have treated male and female participants aged 20–33 as a unified cohort,^34,35 supporting the appropriateness of the participant selection in this study. Before the experiment, all participants received comprehensive information detailing the experimental procedures, potential risks involved and measured to ensure confidentiality. Prior to their involvement in the study, each participant provided informed consent, ensuring their voluntary participation. Furthermore, participants were explicitly instructed to refrain from consuming alcohol or caffeinated products for a minimum of 12 h before the experiment to reduce potential confounding effects.

Table 1.

Participants’ information (n = 48).

	Males		Females
	M ± SD	Range	M ± SD	Range
Age	18.67 ± 1.16	18–20	24 ± 1.35	22–27
Height (cm)	173.33 ± 2.89	170–175	164.00 ± 6.63	156–173
Weight (kg)	64.33 ± 3.79	60–67	53.22 ± 6.01	48–65
BMI (kg/m²)	21.23	19.56–22.69	21.16	20.04–22.13

BMI: body mass index.

Environments

Equipment

Participants used the HTC Vive Pro for scene simulation and immersive experience. The device offered a total resolution of 2880 × 1660 pixels, a 90 Hz refresh rate and a 110° field of view. Throughout the experiment, participants were instructed to wear a BP monitor (Yuwell YE660, error: ±4 mm Hg) and an electrocardiogram (ECG) device (Healink-R211B, 1000 Hz sampling rate).

VR environments

The experimental scene was based on a real street environment, which was then modelled using SketchUp2019 software. Figure 1 illustrates the virtual streets as observed through the VR device. The objective was to investigate the impact of streets with varying W/H ratios on pedestrian stress recovery, and as such, five distinct W/H ratios were selected: 0.5, 1.0, 1.5, 2.0 and 4.0. These values were selected based on the range proposed in the work of Ashihara in Street Aesthetics and were further informed by the findings from the study by Lindal et al.^10,36 In the virtual model, each side of the street featured a residential area, with each block measuring 96 m in length. The structures flanking both sides of the street were uniform in structure, varying in height from 1 to 5 storeys, and their individual heights were influenced by the roof type (flat or sloped). Two buildings were deliberately placed at the street's end to create an enclosed space. Importantly, the street width was set at 12 m, while the total height of the buildings on both sides ranged from 3 to 24 m. To prevent the study from being affected by building shadows, the sunshine parameters were calibrated to simulate the conditions at noon on 21 June, the summer solstice, when the sun is at its zenith in the Northern Hemisphere sky. The virtual camera was placed at the centre of the street's near end, positioned at a height of 1.75 m to replicate the eye-level perspective of an average-height adult. Notably, the virtual streetscape deliberately excluded any presence of cars, people or animals.

Figure 1.

VR streets with different W/H ratios.

Procedures

The study was carried out from 4th to 31st July 2022, between 8:00 and 12:30 am. A total of 48 participants were recruited and randomly assigned to various test orders. Each participant entered the laboratory individually. Figure 2 illustrates the experimental process. During the initial stage, participants were equipped with BP and HRV physiological monitoring devices and instructed to maintain a stationary position for 10 min to minimize any early-stage activity interference. Then, the trier social stress test (TSST) was administered. The TSST, a widely used approach for inducing stress, involved two tasks: first, participants rapidly determined whether the word meaning and colour corresponded correctly, followed by performing additions and subtractions of values below 1000. The entire stimulation process lasted for 10 min. During the third stage, participants donned VR headsets and observed a randomly assigned experimental scene for a duration of 3 min, during which HRV data were continuously monitored and recorded. BP measurements were taken at the outset and conclusion of this stage. In the fourth stage, after viewing the scene, participants completed the RCS. The experiment was repeated using various scenes, with their sequence randomized.

Figure 2.

Experimental process.

Psychological indicators

To evaluate the subjective stress recovery, we utilized the RCS, which is adapted for assessing environmental restoration. The RCS was derived from the four environmental dimensions outlined in Attention Restoration Theory: being away, fascination, extent and compatibility.³⁷ Earlier studies have demonstrated the RCS's efficacy in examining expectations and current levels of street recovery.³⁸ Consisting of 15 items, participants provided their ratings using a 7-point Likert scale, spanning from −3 (no sensation) to 3 (very strong).

Physiological indicators

Blood pressure

Arterial BP serves as an essential indicator of the cardiovascular system's functional status, with SBP and DBP values providing insights into the prevailing pressure levels. Due to the significant influence of time on SBP and DBP, certain studies propose the incorporation of PBP as a pertinent predictor of health outcomes.^39,40 PBP, defined as the disparity between SBP and DBP, offers valuable information in this context.

Heart rate variability

HRV has a pivotal role in assessing an individual's stress level by reflecting the activity of the SNS and the parasympathetic nervous system (PNS).^41,42 To obtain continuous single-channel ECG data, an ultra-light portable ECG dynamic measurement (Heallink, China) was used. Subsequently, the acquired data underwent processing by Kubios software. For the assessment of participants’ stress recovery, three HRV parameters were carefully selected and included in the analysis: LF/HF,^43,44 pNN50⁴² and RR,⁴⁵ as presented in Table 2.

Table 2.

HRV indicator definition.

Index	Definition	Relationship
LF/HF	The frequency domain parameters include low frequency (LF; 0.04–0.15 Hz) and high frequency (HF; 0.15–0.40 Hz)	An elevated LF/HF reflects increased SNS activity and a heightened state of arousal
pNN50	The proportion of consecutive heartbeat intervals that surpass 50 ms	An elevated pNN50 value signifies enhanced PNS activity and a more relaxed physiological condition
RR	Sequential normal R–R intervals	A prolonged RR interval reflects enhanced PNS relaxation

SNS: sympathetic nervous system; PNS: parasympathetic nervous system.

Statistical analysis

To comprehensively investigate the diverse effects of street W/H ratios on physical and mental recovery, Spearman correlation analysis was performed on the collected psychophysiological data utilizing SPSS 27.0 software. The correlation strength was measured using the correlation coefficient (r), which ranges from −1 to 1, with r > 0 indicating a positive relationship and r < 0 signifying a negative relationship. The results were classified into five levels based on the correlation coefficient: (i) 0–0.09: negligible; (ii) 0.10–0.39: weak; (iii) 0.40–0.69: moderate; (iv) 0.70–0.89: strong; (v) >0.90: very strong.³⁴ Moreover, to explore the differences amongst different W/H ratios, we employed one-way ANOVA. The significance of correlation and ANOVA was determined by the p-value, divided into three levels: (1) p < 0.001: highly significant; (2) p < 0.01: significant; (3) p < 0.05: weakly significant.⁴⁶

Results and discussion

Influence of W/H of street on physiological responses

Figure 3 illustrates variations in RCS scores in relation to streets with different W/H ratios. With the exception of W/H = 0.5, all other streets with varying W/H ratios were subjectively perceived to offer certain restorative benefits, as evidenced by scores greater than 0. Amongst these, W/H = 1.5 attained the highest RCS scores (1.05) and was deemed most conducive to stress recovery. Streets with W/H ratios of 2.0 and 1.0 followed closely, with RCS scores of 1.03 and 0.89, respectively. A noticeable observation is that streets with W/H ratios within the range of 1.0–2.0 demonstrated superior subjective recovery compared to streets with W/H ratios of 0.5 and 4.0, with RCS scores elevated by 1.02–1.18. These differences showed statistical significance (p < 0.05, see Table 3). The above findings further corroborate the assertion by Ashihara³⁶ that streets with W/H ratios of 1.0–2.0 offer a more comfortable experience and foster enhanced stress recovery. Additionally, other scholars have also highlighted the high preference for street W/H in this range, as it appears to stimulate pedestrian interest in walking and promote health recovery.

Figure 3.

Variations in RCS concerning streets with different W/H ratios. RCS: Restorative Components Scale.

Table 3.

ANOVA for RCS in relation to streets with different W/H ratios.

W/H	0.5	1.0	1.5	2.0	4.0
0.5	1
1.0	0.000***	1
1.5	0.000***	0.000***	1
2.0	0.000***	0.430	0.947	1
4.0	0.019*	0.469	0.000***	0.000***	1

ANOVA: analysis of variance; RCS: Restorative Components Scale.

***p < 0.001; *p < 0.05.

Figure 4 presents the variations in scores for being away, fascination, extent/ and compatibility concerning streets with different W/H ratios. Amongst the streets with different W/H ratios, those falling within the range of 1.0–2.0 exhibited the most notable improvements in all four psychological indicators. Specifically, streets with W/H ratios of 1.0 and 1.5 demonstrated the highest scores for being away (1.23). Existing research indicates that streets with W/H ratios between 1.0 and 2.0 offer the highest visual comfort and provide a better perceived experience for pedestrians.⁴⁷ The street with a W/H of 2.0 was found to be the most preferred in terms of fascination (1.27), followed closely by streets with W/H ratios of 1.0 and 1.5 (0.91–0.95). In contrast, streets with a W/H of 4.0 obtained a low score for fascination (0.14). Excessively large W/H ratios tend to create a sense of emptiness, diminishing the street's attractiveness.¹⁷ Regarding extent and compatibility, the street with a W/H of 1.5 achieved the highest scores at 0.77 and 1.27, respectively. These characteristics attract young people to engage in activities, enjoy social interactions, temporarily forget their troubles and facilitate stress recovery. The results of ANOVA in Table 4 revealed significant distinctions between W/H = 0.5 and other streets concerning being away, fascination and compatibility (p < 0.05), indicating that the positive impact on stress recovery was marginal. This observation aligns with Stamps et al.’s^17,48 findings that people generally disfavour closed environments with limited visual fields, as excessively narrow W/H ratios instigate feelings of pressure and hinder recovery. Overall, compared to W/H ratios of 0.5 and 4.0, streets with W/H ratios of 1.0–2.0 exhibit greater restorative benefits. Amongst these, streets with a W/H of 1.5 obtained the highest scores in the evaluation of being away, extent and compatibility, which corresponds better to features of a restorative environment.

Figure 4.

Variations in scores for different ART dimensions for streets with different W/H ratios. ART: attention restoration theory.

Table 4.

ANOVA for different ART dimensions for streets with different W/H ratios.

	W/H	0.5	1.0	1.5	2.0	4.0
Being away	0.5	1
	1.0	0.604	1
	1.5	0.002**	0.011*	1
	2.0	0.007**	0.029*	0.697	1
	4.0	0.002**	0.011*	0.899	0.697	1
Fascination	0.5	1
	1.0	0.119	1
	1.5	0.000***	0.028*	1
	2.0	0.000***	0.001**	0.297	1
	4.0	0.000***	0.020*	0.896	0.361	1
Extent	0.5	1
	1.0	0.611	1
	1.5	0.254	0.525	1
	2.0	0.611	0.899	0.525	1
	4.0	0.446	0.799	0.703	0.799	1
Compatibility	0.5	1
	1.0	0.018*	1
	1.5	0.000***	0.000***	1
	2.0	0.000***	0.000***	0.881	1
	4.0	0.000***	0.026*	0.179	0.179	1

ANOVA: analysis of variance; ART: attention restoration theory. ***p < 0.001; **p < 0.01; *p < 0.05

In general, streets with W/H ratios ranging from 1.0 to 2.0 demonstrated higher potential for stress recovery when compared to those with W/H ratios of 0.5 and 4.0. Notably, the street with a W/H of 1.5 stood out as particularly restorative, providing individuals with an opportunity to distance themselves from the stress and challenges of daily life while fostering positive and beneficial associations.

Influence of W/H of street on psychological responses

Blood pressure

Figure 5 shows variations in BP in relation to streets with different W/H ratios. Excluding W/H = 0.5, other W/H ratios demonstrated more favourable stress recovery effects on BP. Particularly, W/H = 1.0 exhibited the most significant decrease in SBP, with a reduction of 2.18 mm Hg, followed by the street with a W/H of 1.5, which showed a decrease of 1.45 mm Hg. Fang et al.⁴⁷ also reported that W/H = 1.0 evoked the strongest positive emotions and provided a superior pedestrian experience. Regarding DBP, W/H = 2.0 exhibited the most significant reduction, exceeding that of W/H = 0.5 by 1.28 mm Hg. In terms of PBP, except for W/H = 0.5, all other W/H ratios showed reductions in PBP (0.07–0.86 mm Hg), with W/H = 2.0 having the most pronounced effect, resulting in the largest decrease in pressure levels. Overall, streets with W/H ratios of 1.5 and 2.0 effectively facilitated the reduction of SBP, DBP and PBP (0.09–1.45 mm Hg), making them more beneficial for cardiovascular protection and health recovery.⁴⁹ These findings align with existing research conclusions, indicating that streets with W/H ratios ranging from 0.75 to 2.0 exhibit better cohesion and prevent pedestrians from experiencing feelings of emptiness and depression. Moreover, the street with a W/H of 2.0 allows pedestrians to better appreciate the architectural features of buildings along the street and fosters physical and mental recovery.⁴⁷

Figure 5.

Variations in BP in relation to streets with different W/H ratios. BP: blood pressure.

Heart rate variability

LF/HF.

Figure 6 shows variations in LF/HF in relation to streets with different W/H ratios. Streets with W/H ratios of 1.0–2.0 exhibited the most substantial decrease in LF/HF, reaching 0.63–0.65, signifying a superior decompression effect compared to streets with W/H ratios of 0.5 and 4.0. During the initial minute, the street with a W/H of 4.0 demonstrated the swiftest decline in LF/HF, as the open street scene fostered a sense of proximity to nature, resulting in rapid recovery within a brief timeframe. However, as time progressed, the broader visible sky area impacted safety cognition, heightened vigilance and impeded stress recovery.⁵⁰ Conversely, W/H = 0.5 experienced an increase in LF/HF, indicating that narrow streets intensified the mental stress of pedestrians. Although stress levels diminished after a short adaptation period, they remained elevated. Yao et al.²⁰ also observed that crowded street spaces could elicit negative perceptions and experiences, increasing the sense of tension and pressure. After 3 min, streets with W/H ratios of 1.5 and 1.0 displayed smaller LF/HF (0.75–0.76), indicative of lower pressure levels. Comfortable street environments modulated the SNS and PNS balance of the ANS towards increased SNS activities, thereby supporting pedestrian recovery.^45,49 In conclusion, streets with W/H ratios of 1.0 and 1.5 share similar mechanisms of stress relief and yield more favourable recovery effects. Conversely, excessively narrow streets (W/H = 0.5) prompt an instantaneous increase in individual stress levels, which is unfavourable for psychological and physiological health.

Figure 6.

Variations in LF/HF in relation to streets with different W/H ratios.

pNN50

Figure 7 shows variations in pNN50 in relation to streets with different W/H ratios. In descending order, pNN50 ranked the streets with W/H ratios of 1.0, 1.5, 2.0, 4.0 and 0.5. Higher pNN50 values indicate lower stress levels, and notably, W/H = 1.0 demonstrated the most effective stress reduction, with pNN50 being 2.40% higher compared to W/H = 0.5, followed by W/H = 1.5 (16.80%). In general, W/H ratios ranging from 1.0 to 2.0 exhibited a stronger match with the features of a restorative environment, which is consistent with the findings presented in Street Aesthetics.³⁶

Figure 7.

Variations in pNN50 in relation to streets with different W/H ratios.

RR.

Figure 8 shows variations in RR in relation to streets with different W/H ratios. The ratio W/H = 2.0 exhibited the highest RR, reaching 773.10 ms, followed by W/H = 1.0 (771.13 ms), indicating superior stress relief effects. The stress recovery benefits of W/H ratios = 1.5 and 4.0 were comparable, ranging from 767.36 to 768.60 ms. This indicated that streets with W/H ratios within the range of 1.0–2.0 offered the most favourable experience and contributed significantly to enhanced health promotion. Conversely, W/H = 4.0 demonstrated a slightly superior decompression effect compared to W/H = 0.5, attributed to the wider field of view provided by the former, in contrast to the more crowded street environment of the latter.

Figure 8.

Changes in RR concerning streets with different W/H ratios.

Overall, streets with W/H ratios of 1.0–2.0 exhibited improved recovery in HRV, with enhanced PNS activity, which could aid in reducing cardiovascular risk and promote pedestrian health. Additionally, the street with a W/H of 4.0 also contributed positively to stress recovery due to their wider sight lines. However, an excessively large visible sky area may hinder the provision of a desirable sense of enclosure, leading to increased stress levels.⁵¹ Additional research is needed to explore the specific effects of these factors.

Correlation analysis

In Table 5, LF/HF exhibited a moderate positive correlation with RCS (r = 0.64, p < 0.01), while showing negative correlations with scores for being away, fascination, extent and compatibility. Additionally, pNN50 demonstrated a significant correlation with RCS (r = 0.203). These findings highlight a consistent trend between psychological and physiological indicators regarding stress recovery. The consistency is linked to the interaction between physiological arousal and emotional responses, with restorative environments enhancing positive emotions and alleviating autonomic stress responses.⁵²

Table 5

Correlation analysis of psychophysiological indicators for various street W/H ratios.

		Physiological indicators
r		Being away	Fascination	Extent	Compatibility	RCS
Psychological indicators	LF/HF	−0.347**	−0.477**	−0.272**	−0.426**	−0.640**
	pNN50	0.129	0.184	0.082	0.085	0.203*
	RR	−0.109	−0.144	0.178	−0.061	−0.067
	SBP	−0.005	−0.109	0.112	0.029	−0.081
	DBP	−0.116	−0.040	0.075	−0.084	−0.072
	PBP	0.111	0.205*	0.115	−0.157	0.117

***p < 0.001; **p < 0.01.

The optimal street W/H

The research findings indicated that streets with W/H ratios between 1.0 and 2.0 possess attributes in line with the restorative environment. These attributes could facilitate the alleviation of daily pressures, allowing individuals to experience both physical and mental relaxation. Both the RCS and physiological indicators (BP and HRV) demonstrated favourable stress recovery benefits. However, due to the similar effects observed, an optimal threshold has not yet been determined. To elucidate the underlying mechanisms through which street W/H could influence stress recovery, a correlation model between street W/H and stress recovery has been developed. Based on the correlation analysis, LF/HF showed a highly positive correlation with all subjective assessments (p < 0.01), signifying a strong relationship. Thus, LF/HF was selected as the evaluation index for predicting the optimal W/H. Figure 9 shows the fitting curves of LF/HF and street W/H. An extreme function model of equation (1) was derived by analysing the LF/HF difference before and after the participants view street scenes. The fitting coefficient R² was 0.87, indicating a good fit for the model:

y = 0.23 + 0.6 e^{- e^{- z} - z + 1}

(1)

where z is (W/H − 1.25)/0.33, 0.5 ≤ W/H ≤ 4.0. Significantly, at the y’s peak, LF/HF underwent a notable decrease, resulting in a considerable reduction in stress levels. Consequently, for W/H ranging from 0.5 to 4.0, when W/H = 1.25, it is deemed to be the most favourable condition for stress recovery.

Figure 9.

Fitting curve of LF/HF and street W/H.

Limitations and future research

As far as we know, this is the first study to investigate street W/H ratios and stress recovery by combining VR and multiple psychophysiological indicators, which contributes to the human-centred design of urban spaces. However, the study has some limitations. Although the study included data from 48 participants, meeting the minimum sample size requirement, expanding the sample size in future studies is essential to improve the generalizability of the findings. Additionally, all participants were university students, representing only a portion of this age group. Future studies should encompass a broader range of age groups. Notably, while the study found that the optimal W/H ratios indicated by different measures were all within the range of 1.0–2.0, there were variations in the specific values. This may be related to individual differences in environmental preferences and warrants further exploration. Although VR has been proven to effectively replicate street environments with high fidelity, differences still exist compared to real street environments. To improve the practical applicability of the results, future research should focus more on real street environments. Additionally, street spaces are complex environments where factors like building facade design and traffic flow could impact restoration and warrant further investigation.

Conclusion

This study aimed to investigate effects of different street W/H ratios on pedestrian stress recovery by testing 48 university students using subjective evaluation metrics and objective physiological indicators. The goal was to determine the optimal W/H that helps alleviate pedestrian stress, thereby providing guidance for the human-centred design of urban streets and the protection and renewal of traditional streets. The conclusions drawn from this study are as follows:

Subjectively, streets with W/H ratios of 1.0–2.0 were perceived as more restorative, exhibiting higher RCS scores ranging from 0.89 to 1.03. Amongst these, the street with a W/H of 1.5 received the highest scores (0.77–1.27) in the dimensions of being away, extent and compatibility, aligning well with the characteristics of restorative environments.

Regarding BP, streets with W/H ratios of 1.5 and 2.0 demonstrated more positive effects on stress recovery, leading to significant reductions in BP. Specifically, SBP was reduced by 0.95–1.45 mm Hg, DBP was reduced by 0.09–1.05 mm Hg, and PBP was reduced by 0.59–0.86 mm Hg.

Regarding HRV, streets with W/H ratios of 1.0–2.0 exhibited significantly better recoverability compared to streets with W/H ratios of 0.5 and 4.0. Streets with W/H ratios of 1.0 and 1.5 showed lower LF/HF (0.75–0.76) and higher pNN50 (16.80–16.97%). Additionally, streets with a W/H of 2.0 had the longest RR (773.10 ms).

Through the application of extreme function fitting, this study revealed that the most substantial stress recovery occurred when the street W/H = 1.25.

Footnotes

Acknowledgements

The authors want to thank those participants who volunteered for the experiments.

Authors’ contribution

All authors contributed equally in the preparation of this manuscript.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Funding

The authors received no financial support for the research, authorship and/or publication of this article.

ORCID iDs

Nan Zhang

Lin Zhao

Genzheng Guan

Chao Liu

References

Bao

Tao

Zeng

Dewancker

. Adapting to changes in the COVID-19 pandemic: research and recommendations on spatial layout and resident experience in MURBs. City Built Environ 2023; 1: 12.

Kang

. Soundscape in city and built environment: current developments and design potentials. City Built Environ 2023; 1: 1.

Zhang

Liu

Wang

Meng

Yao

Gao

. A review of EEG signals in the acoustic environment: brain rhythm, emotion, performance, and restorative intervention. Appl Acoust 2025; 230: 110418.

Beemer

Stearns-Yoder

Schuldt

Kinney

Lowry

Postolache

Brenner

Hoisington

. A brief review on the mental health for select elements of the built environment. Indoor Built Environ 2021; 30: 152–165.

Zhang

Jiao

Liu

Shi

Gao

. Effects of spring water sounds on psychophysiological responses in college students: an EEG study. Appl Acoust 2025; 228: 110318.

Yin

Thwaites

Simpson

. Exploring the use of restorative component scale to measure street restorative expectations. Urban Des Int 2022; 27: 145–155.

Lindal

Hartig

. Effects of urban street vegetation on judgments of restoration likelihood. Urban For Urban Green 2015; 14: 200–209.

Lin

Tsai

Sullivan

Chang

. Does awareness affect the restorative function and perception of street trees? Front Psychol 2014; 5: 906.

Van Dillen

De Vries

Groenewegen

Spreeuwenberg

. Greenspace in urban neighbourhoods and residents’ health: adding quality to quantity. J Epidemiol Community Health 2012; 66: e8.

10.

Lindal

Hartig

. Architectural variation, building height, and the restorative quality of urban residential streetscapes. J Environ Psychol 2013; 33: 26–36.

11.

Bornioli

Parkhurst

Morgan

. Psychological wellbeing benefits of simulated exposure to five urban settings: an experimental study from the pedestrian's perspective. J Transp Health 2018; 9: 105–116.

12.

Bornioli

Parkhurst

Morgan

. Affective experiences of built environments and the promotion of urban walking. Transp Res Part A Policy Pract 2019; 123: 200–215.

13.

Hang

Chen

. Experimental study of urban microclimate on scaled street canyons with various aspect ratios. Urban Clim 2022; 46: 101299.

14.

Huang

Zhuang

. Analysis of height-to-width ratio of commercial streets with arcades based on sunshine hours and street orientation. Appl Sci 2021; 11: 1706.

15.

Chen

Yang

Hang

Lin

Wang

Liu

. The influence of aspect ratios and solar heating on flow and ventilation in 2D street canyons by scaled outdoor experiments. Build Environ 2020; 185: 107159.

16.

Sitte

. The art of building cities: city building according to its artistic fundamentals. Translated by Stewart CT. 1st ed. London: Collins, 1965, pp. 32–50.

17.

Herzog

. A cognitive analysis of preference for urban spaces. J Environ Psychol 1992; 12: 237–248.

18.

Stamps

IAE

. Enclosure and safety in urban scapes. Environ Behav 2005; 37: 102–133.

19.

Alkhresheh

. Enclosure as a function of height-to-width ratio and scale: its influence on user's sense of comfort and safety in urban street space. PhD Thesis, University of Florida, Gainesville, USA, 2007.

20.

Yao

Yuan

Rui

Chen

Duan

Sun

. Research on the scale of pedestrian space in underground shopping streets based on VR experiment. J Asian Archit Build Eng 2020; 20: 138–153.

21.

Kilicaslan

Malkoc

Turel

. Comparative analysis of traditional, modern, and renovated streets in physical, visual, and life aspects: a case study on Buca District – Izmir (Turkey). Indoor Built Environ 2008; 17: 403–413.

22.

Zhang

Zhuo

Wei

Yin

. Emotional responses to the visual patterns of urban streets: evidence from physiological and subjective indicators. Int J Environ Res Public Health 2021; 18: 9677.

23.

Lee

Luo

. The effect of virtual reality forest and urban environments on physiological and psychological responses. Urban For Urban Green 2018; 35: 106–114.

24.

De Brito

Pope

Mitchell

Schneider

Larson

Horton

Pereira

. The effect of green walking on heart rate variability: a pilot crossover study. Environ Res 2020; 185: 109408.

25.

Zhang

Jeng

Zend

. Cityscape protection using VR and eye tracking technology. J Vis Commun Image Represent 2019; 64: 102639.

26.

Liu

Zhang

Shi

Gao

. Preliminary data on effects of different street vegetation on stress recovery. Build Simul 2023; 16: 2109–2121.

27.

Faul

Erdfelder

Lang

Buchner

. G*Power 3: a flexible statistical power analysis program for the social, behavioral, and biomedical sciences. Behav Res Methods 2007; 39: 175–191.

28.

Cohen

. Statistical power analysis for the behavioral sciences. 2nd ed. Abingdon-on-Thames, Oxfordshire, UK: Routledge, 2013, pp. 30–42.

29.

Guan

Mao

Liu

. People's subjective and physiological responses to the combined thermal-acoustic environments. Build Environ 2020; 172: 106709.

30.

Alipour

Abbasalizad Farhangi

Dehghan

Alipour

. Body image perception and its association with body mass index and nutrient intakes among female college students aged 18–35 years from Tabriz, Iran. Eat Weight Disord 2015; 20: 465–471.

31.

Kolawole

Kevin

Oluwole

Ademola

. The association of socio-demographic factors with overweight/obesity among students (ages 18–35 years) in Cavendish University, Uganda. Epidemiology 2017; 7: 1000328.

32.

Karadayian

Merlo

Czerniczyniec

Lores-Arnaiz

Hendriksen

Pantea

Bruce

Verster

. Alcohol consumption, hangovers, and smoking among Buenos Aires University students during the COVID-19 pandemic. J Clin Med 2023; 12: 1491.

33.

Jeon

Lee

. Psycho-physiological restoration with audio–visual interactions through virtual reality simulations of soundscape and landscape experiences in urban, waterfront, and green environments. Sustain Cities Soc 2023; 99: 104929.

34.

Wang

Menassa

Kamat

. Investigating the effect of indoor thermal environment on occupants’ mental workload and task performance using electroencephalogram. Build Environ 2019; 158: 120–132.

35.

Deng

Wang

Menassa

. Measurement and prediction of work engagement under different indoor lighting conditions using physiological sensing. Build Environ 2021; 203: 108098.

36.

Ashihara

. The aesthetic townscape. J Aesthet Art Critic 1986; 44: 416–417.

37.

Laumann

Gärling

Stormark

. Rating scale measures of restorative components of environments. J Environ Psychol 2001; 21: 31–44.

38.

Yin

Thwaites

Shao

. Balancing street functionality and restorative benefit: developing an expectation – current approach to street design. Sustainability 2022; 14: 5736.

39.

Benetos

Thomas

Bean

. Role of modifiable risk factors in life expectancy in the elderly. J Hypertens 2005; 23: 1803–1808.

40.

Zhang

Zhao

Shi

Gao

. Impact of visual and textural characteristics of street walls on stress recovery. Sci Rep 2024; 14: 15115.

41.

Zhang

Morère

Sieler

. Reaction time and physiological signals for stress recognition. Biomed Signal Process Control 2017; 38: 100–107.

42.

Jiang

Yongga

Yan

. Short-term effects of natural view and daylight from windows on thermal perception, health, and energy-saving potential. Build Environ 2021; 208: 108575.

43.

Jin

Juan

. Is Fengshui a science or superstition? A new approach combining the physiological and psychological measurement of indoor environments. Build Environ 2021; 201: 107992.

44.

Lei

Yuan

Lau

SSY

. A quantitative study for indoor workplace biophilic design to improve health and productivity performance. J Clean Prod 2021; 324: 129168.

45.

Castaldo

Melillo

Bracale

. Acute mental stress assessment via short-term HRV analysis in healthy adults: a systematic review with meta-analysis. Biomed Signal Process Control 2015; 18: 370–377.

46.

Liu

Zhang

Wang

Pan

Ren

Gao

. Correlation between brain activity and comfort at different illuminances based on electroencephalogram signals during reading. Build Environ 2024; 261: 111694.

47.

Fang

Song

. Reflection of Yoshinobu Ashihara's research about the proportion of street width to building height: a study of street space based on human scale. New Archit 2014; 5: 136–140.

48.

Stamps

IAE

. Visual permeability, locomotive permeability, safety, and enclosure. Environ Behav 2005; 37: 587–619.

49.

Kabisch

Püffel

Masztalerz

Hemmerling

Kraemer

. Physiological and psychological effects of visits to different urban green and street environments in older people: a field experiment in a dense inner-city area. Landsc Urban Plan 2021; 207: 103998.

50.

Fang

. Spatial renewal strategy of urban living street under healing orientation: a case study of Dalian city. PhD Thesis, Dalian University of Technology, Dalian, China, 2022.

51.

Appleton

The experience of landscape. 1st ed. New York: Wiley, 1996, pp. 1–11.

52.

Ulrich

Simons

Losito

. Stress recovery during exposure to natural and urban environments. J Environ Psychol 1991; 11: 201–230.