Which distance-decay function for migration and which one for commuting? A case study of Slovenia

Cycling is a green, sustainable, and healthy choice for transportation that has been widely advocated worldwide in recent years. It can also encourage the use of public transit by solving the “last-mile” issue, because transit passengers can cycle to and from transit stations to achieve a combination of speed and flexibility. Cycling as a transfer mode has been shown to be affected by various built environment characteristics, such as the urban density, land-use mix, and destination accessibility, that is, the ease with which cyclists can reach their destinations. However, cycling destination accessibility is loosely defined in the literature and the methods of assessing cycling accessibility is often assumed to be equivalent to walking accessibility using the same decay curves, such as the negative exponential function, which ignores the competitive relationship between cycling and walking within a short distance range around transit stations. In this study, we aim to fill the above gap by measuring the cycling destination accessibility of metro station areas using data from more than three million bicycle-metro transfer trips from a dockless bicycle-sharing program in Shenzhen, China. We found that the frequency of bicycle-metro trips has a positive association with a trip distance of 500 m or less and a negative association with a trip distance beyond 500 m. A new cycling accessibility metric with a lognormal distribution decay curve was developed by considering the distance decay characteristics and cycling’s competition with walking. The new accessibility model outperformed the traditional model with an exponential decay function, or that without a distance decay function, in predicting the frequency of bicycle-metro trips. Hence, to promote bicycle-metro integration, urban planners and government agencies should carefully consider the destination accessibility of metro station areas.

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Modelling walking accessibility: A case study of Ljubljana, Slovenia

Moravian Geographical Reports ◽

10.2478/mgr-2019-0015 ◽

2019 ◽

Vol 27 (4) ◽

pp. 194-206

Author(s):

Jernej Tiran ◽

Mitja Lakner ◽

Samo Drobne

Keyword(s):

Distance Decay ◽

Integrated Network ◽

Distance Threshold ◽

Transport Distance ◽

Fixed Distance ◽

Different Types ◽

Best Fitting ◽

Retail Services ◽

The City

Abstract Walkable access is recognised as one of the most important factors for deciding to walk instead of using other modes of transport. Distance has been less accurately taken into consideration in previous walking accessibility measures, however, as they are often based on an isotropic approach or on a fixed distance threshold. The objective of this paper is to present a method of modelling continuous walking accessibility to different amenities in a city, with an integrated network-based and distance-decay approach, applied to a case study of the city of Ljubljana, Slovenia. The approach is based on a web survey to obtain data on acceptable walking distances to different types of amenities. Several distance decay functions were analysed for each type of amenity from the cumulative frequency of responses. The best fitting functions were used to model the walking accessibility surfaces for individual amenities in the network, representing five domains (retail, services, recreation, education and transportation) and an overall walking accessibility index. Despite certain limitations and a further need to assess the validity of the methods, our distance-decay network-based approach is more accurate than the isotropic or even network-based modelling of walking distances in continuous or threshold approaches, as it enables the researcher to take into account the differences in propensities to walk to different amenities. The results can be used by city authorities and planners for implementing actions to improve walking accessibility in the most problematic areas.

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A Modified Gravity p-Median Model for Optimizing Facility Locations

Journal of Systems Science and Information ◽

10.21078/jssi-2018-421-14 ◽

2018 ◽

Vol 6 (5) ◽

pp. 421-434 ◽

Cited By ~ 1

Author(s):

Zhuolin Tao ◽

Qingjing Zheng ◽

Hui Kong

Keyword(s):

Modified Gravity ◽

Distance Decay ◽

Decay Parameter ◽

Distance Threshold ◽

Facility Locations ◽

Spatial Equity ◽

Average Travel Time ◽

Tertiary Hospitals ◽

The Difference

AbstractThe gravityp-median model is an important improvement to the widely-usedp-median model. However, there is still a debate on its validity in empirical applications. Previous studies even doubt the significance of the gravityp-median model. Using a case study of tertiary hospitals in Shenzhen, China, this study re-examines the difference between the gravityp-median model with thep-median model, by decomposing the difference between the two models into gravity rule and variant attraction. This study also proposes a modified gravityp-median model by incorporating a distance threshold. The empirical results support the validity of the gravityp-median model, and also reveal that only when the attractions of candidate facility locations are variable will the gravityp-median model lead to different results with thep-median model. The difference between the modified gravityp-median model and the gravityp-median model is also examined. Moreover, the impacts of the distance-decay parameter and distance threshold on solutions are investigated. Results indicate that a larger distance-decay parameter tends to result in a more dispersed distribution of optimal facilities and a smaller average travel time, and a smaller distance threshold can better promote the spatial equity of facilities. The proposed method can also be applied in studies of other types of facilities or in other areas.

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An Analysis of Mobility Patterns in Sexual Homicide

Homicide Studies ◽

10.1177/1088767919884601 ◽

2019 ◽

Vol 24 (2) ◽

pp. 178-202 ◽

Cited By ~ 1

Author(s):

Julien Chopin ◽

Stefano Caneppele ◽

Eric Beauregard

Keyword(s):

Crime Scene ◽

Distance Decay ◽

Mobility Patterns ◽

Spatial Mobility ◽

National Data ◽

Decay Function ◽

Data Set ◽

Sexual Homicide ◽

Safe Place

This article—based on a national data set ( N = 173)—focuses on extrafamilial sexual homicides and their spatial mobility. The study combines the location of the crime scene and the offenders and victims’ residences in mobility crime triangles. The findings reveal that most of the homicides fall within the categories of offender mobility and total mobility. Our results show the validity of the distance decay function, with over 70% of homicides occurring within 10 km of the offender’s residence. It appears that under certain circumstances, sexual murderers perceive their surroundings as a safe place to commit a homicide. Finally, the study proposes a four-category spatial typology of sexual homicide.

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Trap of weights: The reuse of weights in the floating catchment area (FCA) methods to measuring accessibility

F1000Research ◽

10.12688/f1000research.51483.1 ◽

2021 ◽

Vol 10 ◽

pp. 751

Author(s):

Lina Zhang

Keyword(s):

Primary Schools ◽

Catchment Area ◽

Distance Decay ◽

Geographic Patterns ◽

Job Opportunities ◽

Resource Type ◽

The Stability ◽

Model Features ◽

The Impact

Background: Geographic weights are vital in the floating catchment area (FCA) method of accessibility measurements due to their simulation of spatial barriers in various ways. When modelling population demand, geographical weights with different distance decay coefficients can reflect diverse distance tolerances in facility utilization and could lead to erratic accessibility results. Quantifying accessibility as the sum of weighted supply-demand ratios can alleviate the distance decay coefficient's influence and generate stable geographic patterns. However, the effects of weighted ratios on different FCA models and resources have not been investigated. Methods: To identify impacts of weighted ratios on various FCA variants, this study contrasted the accessibility calculated from the sum of ratios (access) and the sum of weighted ratios (access ratios) within three prevalent FCA models: enhanced two-step FCA (E2SFCA), modified two-step FCA (M2SFCA), and three-step FCA (3SFCA). In addition, the accessibilities of various resources evaluate the stability of the weighted ratios' effect. This study therefore examined the accessibilities to primary schools, job opportunities, and major hospitals in Shanghai. Shanghai is a case study that provides lessons on using big data to measure accessibility in metropolitan areas. Results: Geographic weights can not only mitigate the impact of the distance decay coefficients, but can also eliminate model features, which reduces the performance of the M2SFCA's supply decay and the 3SFCA's population demand adjustment in accessibility results. Moreover, weighted ratios tend to overestimate accessibility in marginal communities that lie within fewer catchments, regardless of the resource type. This tendency can lead to an epistemological trap that creates an inaccurate and counter-intuitive perception of resource distribution in a given area. Conclusions: The results identify a gap between the methodological logic and the empirical perception in accessibility measurements. This study concludes that the use of geographic weights needs to be cautious and epistemologically consistent.

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