Urban Streetscape Changes in Portland, Oregon: A Longitudinal Virtual Audit

Abstract

Streetscape imagery has considerable potential for observing urban change. The literature lacks sufficient longitudinal studies, however, on urban change considering human perception and activities. We conducted a longitudinal virtual audit to observe the change in urban liveliness, human activities, and built environment by examining streetscape imagery taken in the late 2000s and the late 2010s in Portland, Oregon. Eleven untrained crowd workers were recruited to provide liveliness ratings of 24,242 streetscape images for both periods. Tabulation, mapping, and multilevel regression analyses were conducted to observe the distribution, changes in liveliness, and the factors affecting these changes. The results confirmed that the city had become livelier during the ten-year study period, which was spatially associated with the increase in pedestrians and cyclists and particular elements of the built environment, such as mid- and high-rise buildings and sidewalk signs. Although these results were somewhat expected, this study’s value lies in confirming the potential of virtual audits conducted using Google Street View Time Machine for retrospectively examining subjective and objective urban change. Caution should be exercised, though, while interpreting urban change as temporal conditions (e.g., season, weather, and irregular events) can potentially bias the results in longitudinal studies.

街景图像在观察城市变化方面具有相当大的潜力。然而, 文献缺乏基于人类感知和人类活动的城市变化纵向研究。我们进行了纵向虚拟审核, 研究了2000年代末和2010年代末在美国俄勒冈州波特兰市拍摄的街景图像, 观察了城市活力、人类活动和建成环境的变化。我们招募了11名未经培训的群众工作人员, 对这两个时期的24,242张街景图像进行活力评级。通过制表、绘图和多层次回归分析, 观察了城市活力的分布和变化以及影响这些变化的因素。结果证实, 在此10年期间, 这座城市变得更加有活力。这种变化在空间上与行人和骑自行车者的增加和建成环境的特定元素有关(例如, 中高层建筑和人行道标志)。这些结果在一定程度上是意料之中的。本研究的价值是, 在回顾性地探讨城市的主观和客观变化中, 本文确认了通过谷歌街景时间机器进行虚拟审核的潜力。然而, 将城市变化解释为时间条件(例如, 季节、天气和不规则事件), 可能会带来纵向研究的偏差。

Las imágenes del paisaje callejero tienen un gran potencial en lo que concierne al cambio urbano. Sin embargo, la bibliografía relacionada con este tópico es pobre en estudios longitudinales suficientes sobre el cambio urbano en lo que toca con las percepciones y actividades humanas. Efectuamos una auditoría virtual longitudinal para observar los cambios en vitalidad urbana, las actividades humanas y el entorno construido, examinando las imágenes del paisaje callejero tomadas a finales de los años 2000 y 2010 en Portland, Oregón. Se contrataron once trabajadores sin experiencia para que calificaran la vitalidad de 24.242 imágenes del paisaje callejero en los dos períodos de observación. Se realizaron análisis de tabulación, mapeo y regresión a multinivel para observar la distribución y los cambios en vitalidad, y los factores que afectaban aquellos cambios. Los resultados confirmaron que la ciudad ha adquirido mayor vitalidad durante el período de estudio de diez años, lo cual estuvo asociado espacialmente con un incremento en el número de peatones y ciclistas, y con elementos particulares del entorno construido, tales como edificios de mediana y mayor altura, y señalización en las aceras. Aunque en cierta manera estos resultados eran esperados, la valía del estudio se encuentra en la confirmación del potencial de las auditorías virtuales, llevadas a cabo mediante el uso de la máquina del tiempo de Google Street View para examinar de manera retrospectiva el cambio urbano subjetivo y objetivo. Sin embargo, debería tenerse cautela a la hora de interpretar los cambios urbanos, puesto que las condiciones temporales (e.g., estación, el tiempo meteorológico y los eventos irregulares) pueden potencialmente sesgar los resultados en estudios longitudinales.

Key Words:

• liveliness
• Portland
• streetscapes
• urban change
• virtual audit

关键词:

• 活力
• 波特兰
• 街景
• 城市变化
• 虚拟审核

Palabras clave:

• auditoría virtual
• cambio urbano
• paisajes callejeros
• Portland
• vitalidad

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by JSPS KAKENHI, Japan (Grant Numbers JP17H00947, JP18KK0371, and JP20H00040).

Notes on contributors

Tomoya Hanibuchi

TOMOYA HANIBUCHI is an Associate Professor in the Department of Geography, Kyoto University, Kyoto, Kyoto 606-8501 Japan. E-mail: [email protected]. His research interests include urban geography, health geography, and survey methodology.

Shohei Nagata

SHOHEI NAGATA is an Assistant Professor in the International Research Institute of Disaster Science, Tohoku University, Sendai, Miyagi 980-8572 Japan. E-mail: [email protected]. His research interests include health geography, GIScience, urban informatics, and disaster science.

David Banis

DAVID BANIS is an Associate Director in the Center for Spatial Analysis & Research, Portland State University, Portland, OR 97201. E-mail: [email protected]. His research interests include applied GIS, map design, cultural geography, and natural resource management.

Hunter Shobe

HUNTER SHOBE is a Professor in the Department of Geography, Portland State University, Portland, OR 97201. E-mail: [email protected]. His research interests include cultural geography, urban geography, cultural cartography, sense of place, urban landscapes, public space in the city, place-based branding and marketing, geographies of graffiti and murals, place-based identities and sport, and nationalism.

Tomoki Nakaya

TOMOKI NAKAYA is a Professor in the Graduate School of Environmental Studies, Tohoku University, Sendai, Miyagi, 980-8572 Japan. E-mail: [email protected]. His research interests include GIScience, spatial epidemiology, and health geography.