Visualizing pedestrian flows using GPS-tracking
to improve inner-city quality (No. 200)
Authors
Tine van Langelaar and Stefan van der Spek
Affiliation and contact
Langelaar, Christine Maria van – BBA BBE MSc Urbanism graduation student
E-mail: [email protected] (corresponding author) Spek, Stefan Christiaan van der – MSc PhD
Assistant professor of Urban Design E-mail: [email protected]
Delft University of Technology, Faculty of Architecture, Department of Urbanism
Julianalaan 132-134, PO BOX 5043, 2600 GA DELFT, the Netherlands, Office BG.West.800
Abstract
Every environment has its own characteristics and people react individually to that structure; in an interactive, passive or avoiding way. This paper focuses on pedestrian movement in the city centre of Delft, the Netherlands. It is dedicated to find new and exciting ways of improving city centres for pedestrians by using a Global Positioning Systems (GPS) tracking system. The main role is to develop proposals based on evaluated visitor experiences and to observe the use of public space. This research is related to earlier studies of pedestrian behaviour like Pedestrian mobility and the regeneration of the European city centre. Street-level desires: Discovering the city on foot (Van der Hoeven et al., 2008) and Urbanism on track: Application of tracking technologies in urbanism (Van Schaick et al., 2008). It is directly linked with submitted papers from Stefan van der Spek and Ohyoon Kwon.
The aim of this paper is to inventory, analyze and understand how the city centre of Delft is used by three different groups of pedestrians; city visitors most likely show different behaviour than neighbourhood residents and these will differ from city centre inhabitants. Questions like: “How do pedestrians use the city centre of Delft?”, “What is the current quality of the public space and built environment in the city centre of Delft?”and “Which spatial design interventions can improve public space for pedestrians in order to retain city visitors in the city centre of Delft by using GPS tracking technology?” are answered by using methods like GPS tracking, questionnaires and trip diaries. Pedestrian movement will be visualized and mapped with regard to trips, duration and destination. Thereafter, the paper provides a spatial quality analysis of the inner city of Delft using
photographs.
The outcome of this paper contains the use of the city centre of Delft by three different groups of pedestrians. When these results are combined with the visual quality analysis, flaws and strengths in the urban fabric can be found. Certain areas and streets are used frequently while others are undesirable ignored. Consequently, street life can be improved by making spatial
recommendations and strategic design interventions. The city centre of Delft will therefore become more attractive and more people will stay longer, have a good time and spend more money. City life will flourish.
Key words
– Pedestrian movement; visualization; historic city centre; GPS tracking; critical
positive and negative quality factorsBiography
Tine van Langelaar currently works on her MSc Urbanism graduation project “Measure, know and improve; visualizing pedestrian flows to improve inner-city quality in Delft using GPS-tracking technology.” at TU Delft. After graduation she would like to continue doing research on urban problems in a company or through a PhD.
Stefan van der Spek is lecturer and researcher at TU Delft in the field of Urban Design. His central subject is Pedestrians, Flows and Public Space. His main areas of interest are transit oriented development (stations) and vital city centers.
Tracking Delft are experimental pilot projects with GPS-tracking which are carried out by TU Delft students for the elective course "Urban Design: People, Pedestrians & Public Space”. More information: http://bk.tudelft.nl/trackingdelft (Dutch only)
Visualizing pedestrian flows using GPS-tracking
to improve inner-city quality (No. 200)
Authors
Tine van Langelaar and Stefan van der Spek
Affiliation and contact
Langelaar, Christine Maria van – BBA BBE MSc Urbanism graduation student
E-mail: [email protected] (corresponding author) Spek, Stefan Christiaan van der – MSc PhD
Assistant professor of Urban Design E-mail: [email protected]
Delft University of Technology, Faculty of Architecture, Department of Urbanism
Julianalaan 132-134, PO BOX 5043, 2600 GA DELFT, the Netherlands, Office BG.West.800
Introduction
Every environment has its own characteristics and people react individually to that structure; in an interactive, passive or avoiding way. Local behaviour depends on cultural, social, demographical, economical, physical and political aspects. People’s behaviour in a certain area can be measured and mapped in order to gain knowledge about their movements. It is unknown yet how
pedestrians move through the city centre of Delft, what their routes and destinations are and how much time they spend on the streets. This research is adding information about another historic European city centre in the idea of the ‘Spatial Metro’ project (Van der Hoeven et al., 2008). Cities like Norwich, Bristol, Rouen, Koblenz and Biel/Bienne have been analysed previously. Delft has the same organic structure as its predecessors and has about the same size; approximately 100,000 inhabitants.
If human behaviour in relation to the context is better understood, then governments can manage city centres in such a way that it will be more attractive for visitors and inhabitants. Pedestrians feel more at ease, are happier and enjoy being in a city centre. Eventually, pedestrian models for urban environments can be made to predict behaviour and guide it in desired directions. Street life will flourish and city centres will become more safe because there are more eyes on the street (Jacobs, 1961; Gehl, 1971; Alexander et al., 1977; Bosselmann, 2008). Urban economics will improve as longer visits mean more money spending (Van der Hoeven et al., 2008). Give the streets back to the people. Street activity and quality are critical for urban life in today’s society (Gehl et al., 2006-a).
Based on the geographical origin of participants, a distinction of three different pedestrian groups is made for this research: tourists/visitors, neighbourhood residents and city centre inhabitants. The first research question is: “How do pedestrians use the city centre of Delft?”. Similarities and differences between these three groups of pedestrians and their use of the city centre of Delft can be analysed and mapped. One can think about used and ignored areas, how long trips take, visited destinations, et cetera.
Second, behaviour is easier and faster to understand if the surroundings are well analysed. Certain city parts attract more pedestrians than others. Subsequently, the following research question is: “What is the current quality of the public space and built environment in the city centre of Delft?” What does it look like on the streets and which qualities are found there? After these questions are answered, the main research question rises: “Which spatial design interventions can improve public space for pedestrians in order to retain city visitors in the city centre of Delft by using GPS tracking technology?”
In order to answer the first question two research pilots have been done using GPS-tracking technology (temporal-geographical information), questionnaire surveys and trip diaries (social-geographical information). Results consist of visualised GPS-tracks (GIS maps) and facts & figures (SPSS statistical analysis).
The first research pilot refers to the name “Tracking Delft 1” on the poster. Here, visitors of the city centre of Delft were followed in November 2009. It concerned 325 people who arrived by car, parked it in a garage and continued their trip on foot. This was done during 4 days. The second research pilot refers to the name “Tracking Delft 2” on the poster. Here, neighbourhood residents and city centre inhabitants of Delft were followed during 4 days in April/May 2010. A total amount of 570 trips was gathered and 78 residents (42 households) participated. Every movement and all transportation modes outside the house were recorded. Only the trips on foot were selected for this paper.
The approach to the fieldwork in historic city centres as well as households can be found in previously written literature (Van der Hoeven et al., 2008; Van Schaick et al., 2008; Van der Spek et al., 2009, p. 3038). All outcomes should be considered as results of the involved participants. The study does not give insight in the background and behaviour of all visitors, but only for the selected group.
In order to answer the second question, pictures of streets were made and city life was visually criticised using positive and negative factors which were mapped (Gehl et al., 2006-b). All images are made by the authors unless stated otherwise. Hereafter, results and conclusions were
transformed into spatial design interventions in order to answer the main research question. The next section deals with the city centre use by tourists and other visitors of the city centre of Delft. Functions and results were mapped in order to draw conclusions. The third section reviews the inhabitants of the city centre of Delft as well as residents who live in the surrounding
neighbourhoods. Preliminary results of city centre and neighbourhood participants who visited the city centre of Delft are shown, analysed and discussed. Subsequently, section four looks at the visual quality analysis of the city centre of Delft. What do pedestrians experience when they walk through streets, squares and alleys? Ultimately, the use of the city is combined with the quality analysis which results in spatial recommendations and design interventions for the city centre of Delft in the last section.
City centre use: tourists and other visitors of the city centre of Delft
Figure 1 shows the location of both garages which were the starting points for pedestrian
movement. When the zip code data of the participants was mapped (figure 2) it was striking that there still are people who live close to the city centre and take the car to visit the area. An explanation is that inhabitants went to the large supermarket that is located just above the Zuidpoort garage.
Another possibility is that it concerned a group of (an) adult(s) with young children. Taking the car then is the easiest way of transportation. In order to find out how walking city centre inhabitants move through the city centre a second research pilot was done.
Figure 3: Inventory of retail, leisure (left) and places of interest (right) in the city centre of Delft In order to understand where pedestrians go, an analysis of the city centre of Delft was made. Retail, leisure and places of interest were mapped (figure 3). Some final results of the first pilot can be found in figures 4 - 12. The full report is an intermediate version which focuses on the analysis and findings of the GPS and interview data, conclusions and spatial interventions. If you are interested to learn more about the project and its results, feel free to contact us.
Figure 4: Density analysis Phoenix garage on a Wednesday (left) and Thursday market day (right) Image 4 (left) shows a density analysis of the Phoenix garage on a Wednesday. The majority of the pedestrians leave the garage by the Nieuwstraat. The Choorstraat (north) and
Vrouwjuttenland (east) are boundaries in pedestrian movement. With the exception of the Barbarasteeg, the entire south-west part of the inner-city is ignored.
Low density
Image 4 (right) shows a density analysis of the Phoenix garage on a Thursday. Pedestrian movement on Thursday clearly altered from the usual pedestrian pattern as the Grote Markt and the Brabantse Turfmarkt are frequent and intensely used due to the markets. The markets attract not only pedestrians to the Grote Markt but also further to the south and west. The area around the Army Museum, Breestraat and Achterom are used now. Orientation is east-west.
Figure 5: Density analysis Zuidpoort garage on a Wednesday (left) and Thursday market day (right) Image 5 (left) shows a density analysis of the Zuidpoort garage on a Wednesday. It clearly
distinguishes that Vestpoort and Bastiaanpoort are both used to exit the Bastiaansplein. In general, pedestrians walk in line with these streets. Pedestrian movement on Thursday clearly altered from the usual pattern.
Image 5(right) shows a density analysis of the Zuidpoort garage on a Thursday. Pedestrians from Zuidpoort are also drawn further to the west on this day. Pedestrian movement is also here limited to the Choorstraat. The orientation is in the north-south direction. Therefore the east and west areas are not used to their full potential, based on the analysis of the land-use plan.
Above: visitors leaving garage to visit Grote Markt area Beyond: visitors leaving garage to visit Bastiaansplein area
Figure 6: Heat maps and destinations in the city centre of Delft Phoenix Phoenix Zuidpoort Zuidpoort Low density High density
The heat maps in figure 6show different areas visited by pedestrians from the two garages in relation to a set of defined destinations. The intensity of the red columns together with the height expresses the number of visitors. Relatively more people from the Phoenix garage go to the Grote Markt. Visitors of the Brabantse Turfmarkt and the Jacob Gerritsstraat come from both garages in equal amounts. The Choorstraat is barely used by pedestrians leaving the Zuidpoort garage. Statistics show that both garages are visited mostly by regional inhabitants (figure 7). From the national visitors a percentage of 23% (Phoenix) and 36% (Zuidpoort) live in Delft. The largest part of 50% (Phoenix) and 54% (Zuidpoort) do not live in The Hague, Rotterdam or Rijswijk. Most of the visitors did not have a specific purpose in the inner-city (figure 8). Most pedestrians visited the city centre for the duration of 1-2 hours (figure 9).
Figure 7: Statistics – Origin of visitors
Figure 8: Statistics – Purpose
Figure 9: Statistics - Trip duration
The largest group of pedestrians that visited the city centre was aged 40 – 55 years old (figure 10). For both garages the household situation of ‘partner without children’ was the largest category (figure 11). Pedestrians went into the city ‘alone’ (34% Phoenix and 30% Zuidpoort) or ‘with partner’ (33% Phoenix and 35% Zuidpoort).
Lastly, the Phoenix garage has a percentage of 11% of first time visitors and Zuidpoort 8%. Consequently, most pedestrians visit Delft frequently. Statistics infigure 12show that the majority of visitors who enter the city centre once or twice a month come on Thursday; probably to visit the market. Phoenix Phoenix Zuidpoort Zuidpoort Phoenix Zuidpoort
Figure 10: Statistics – Age
Figure 11: Statistics – Household situation
Figure 12: Statistics – Frequencies Phoenix (left) and Zuidpoort (right) garage
City centre use: neighbourhood and city centre inhabitants of Delft
The question what the favourite transportation mode for trips to the inner city of Delft is, received contradictory answers. First, the questionnaire: 87% on foot, 11% by bike and 2% gave no answer. Second, the GPS data (the used transportation): 25% on foot, 68% by their bike and 7% by car. Questionnaire surveys and GPS tracks sometimes show two different outcomes. When questioned, people tend to give the most socially desired answers instead of the truth (Millonig and Gartner, 2009).
A number of preliminary results can be found in figures 13 - 19. Figures 13 and 14 show used streets and destinations in the city centre of Delft by its inhabitants on foot. Due to local events, Queensday shows different and many more locations than on a normal day are being used. Several differences between city use of city centre and neighbourhood inhabitants can be found. City centre inhabitants tend to ignore the south-western part of the city centre (Barbarasteeg – Breestraat area) while these streets are frequently used by neighbourhood inhabitants.
Neighbourhood inhabitants tend to ignore the south-eastern part of the city centre while city centre inhabitants do use the Oosteinde and Oosterstraat.
City centre inhabitant movement is mainly focused in north-south direction while neighbourhood inhabitants show a dominant east-west motion. Destinations of city centre inhabitants are more spread along several areas while neighbourhood residents seem to concentrate them in some streets.
Phoenix Zuidpoort Phoenix Zuidpoort
Figure 13: Destinations in the city centre by its inhabitants on foot
Figure 14: Destinations in the city centre by inhabitants from neighbourhoods on foot
A similarity can be found in the fact that no pedestrian walks past the Geerweg in the north. This is a boundary, apparently. Also, the area around the Army Museum and the Nieuwe Langendijk are not visited by either party.
Figure 15 shows an access point step depth analysis of the neighbourhood inhabitants on foot by Space Syntax. Red lines represent well connected network roads while blue lines mean bad network connectivity. First, pedestrians make little use of well integrated streets. However, these streets have few functions and since shopping is the main purpose, most streets will not attract that much people.
Moreover, it is striking that there are only four access points to go into the city centre. Even with the flexibility of being on foot, there is a small diversity of chosen east-west routes. In total, there are eleven streets that connect the western neighbourhoods to the city centre.
However, a short analysis shows that only four of these eleven streets are connected to other west-east streets. Seven streets and alleys end on a canal. Routes inside the city centre are blocked by the water and therefore, do not continue.
Figure 15: Access point analysis neighbourhood inhabitants using Space Syntax – on foot
A second argument could be that in two of the four used streets shops can be found. So, it is most likely that pedestrians choose an entrance street with (shopping) functions before they continue their trip into the centre.
Figure 16 demonstrates the destinations of trips inside the city centre of Delft by its city centre inhabitants. Residents mostly go shopping, followed by leisure and drinking & dining.
Figure 16: Destinations of trips inside the city centre of Delft by inhabitants of the city centre Figure 17 looks at destinations in the city centre of Delft by its city centre inhabitants by means of the slow network transportation. It can be concluded that inner-city residents prefer visiting nearby destinations going by foot. Examples are leisure, drinking & dining, dog walking and work. However, when residents go shopping their favourite transportation mode is a bike.
Figure 17: Destinations in the city centre by inhabitants of the city centre, organized by means of the slow network transportation (by bike and on foot)
Figure 18 demonstrates the destinations of trips inside the city centre of Delft by its
neighbourhood inhabitants. Residents mostly go shopping, followed by leisure (specifically on Queensday) and activities related to their children. Figure 19 deals with the choice of
transportation mode to the city centre from the surrounding neighbourhoods. Most favourite travel mode is going by bike (60%) followed by walking (31%). There still is a group of 10% that uses the car for this short movement.
Figure 18: Purpose of trips Figure 19: Transportation mode to city centre
Visual quality analysis
The previous two sections focussed on the movements (‘city use’) of pedestrians in Delft. In this section an analysis of the spatial qualities of the public space in the inner city of Delft is made. This investigation will help explaining why certain streets and areas are used frequently while other spaces are neglected. The analysis concerns a quick scan of the visual quality of the city centre of Delft in order to answer the second research question.
Images were taken to illustrate flaws and good quality of the environment in the city centre of Delft. Streets were analysed using critical positive and negative factors as mentioned previously in literature (Gehl et al., 2006-b). Critical positive factors are: (i) 5 km/h scale (ii) Open (transparency) (iii) Interactive (appealing to many senses) (iv) Rich in sensory experience (v) Diversity of
functions (vi) Vertical façade rhythms. Critical negative factors are: (i) 60 km/h scale (ii) Closed (transparency) (iii) Passive (not appealing to many senses) (iv) Boring (not rich in sensory experience) (v) Uniform functions (vi) Horizontal façade rhythms.
Figure 20 illustrates an overview map where positive and negative factors can be found. What do pedestrians see when they walk around?
Streets and squares
Figure 20: Critical positive factors in green; critical negative factors in red (image by Google Earth) In the city centre of Delft a lot of good quality areas can be found. Figure 21 shows the
Beestenmarkt; a popular busy square. Here are a lot of different activities like shops, eat & drink facilities and leisure. The picture illustrates a skating rink while in summertime the square becomes one huge terrace.
The Grote Markt (figure 22) is a busy square, especially on market days every Thursday. Here are a lot of different activities and functions such as shops, eat & drink facilities and leisure. In
summertime a lot of terraces can be witnessed in front of the cafes. Events like fairs, military shows and weddings in the old Town Hall can be seen here as well (figure 22).
Figure 22: Positive factors – Grote Markt square (left: market day and right: a wedding)
Other attractive streets can be seen in figure 23. Details are designed for a 5 km/h scale, windows are transparent, facades are interactive (appealing to many senses), streets are rich in sensory experience, there is a great diversity of functions and vertical façade rhythms appear.
Figure 23: Positive factors – Vrouwjuttenland, Choorstraat and Cameretten / Voldersgracht
Figure 24: Negative factors – Shopping façade Ezelsveldlaan (photograph by Google Earth) The city centre of Delft has some bad quality streets and areas as well. Just around the Zuidpoort garage the street Ezelsveldlaan is situated (figure 24). It is the perfect example how a ground floor façade should not be designed: the façade is closed regarding transparency, passive and not
appealing to any sense, boring and not rich in sensory experience, uniform functions and partly horizontal façade rhythms. There is no reason to enter this street unless you need groceries from the supermarket.
The façade which measures 90 meters has only one entrance (the green circle in figure 24) instead of every 7-9 meters to enhance urban life (Gehl et al., 2006-b, p. 39). The other four non-transparent doors in the façade are emergency exits. Figure 25shows more examples of
unattractive streets; closed walls, non-transparent windows, passive facades, streets are boring with uniform functions and horizontal façade rhythms.
Figure 25: Negative factors – Kruisstraat, Gasthuislaan and Molslaan
Alleys
The centre of Delft is characterized by a lot of alleys. The first and biggest problem of most alleys is that it is unclear what is going on inside; there is not enough visual contact with the programme at the beginning / end of the street. Not every visitor is waiting for a surprise and do feel unsafe entering such streets.
Figure 26: Alleys – Kromstraat (entrance Jac. Gerritstraat, halfway through and entrance Koornmarkt)
The Kromstraat (figure 26) is a fine example of an alley that partly shows bad quality (graffiti, neglected space and empty buildings) as well as good quality (an art gallery, a children’s shop, new pavement). When the street is entered from the Jacob Gerritstraat there is no programme other than empty buildings and a coffee shop. A sudden change is made when the art gallery and shop appear; the environment becomes livelier. Unexpectedly, the street gets tighter and graffiti can be seen. The feeling of being unsafe returns. Looking at the entrance on the Koornmarkt it looks entirely different than the one on the Jacob Gerritstraat; the width profile narrows down from 4 to 2 meters.
A more extreme example can be found in the Poppesteeg, figure 27. The left picture that shows a clear vision through the alley towards the station (you can see the train passing by). However, halfway through the “eyes” (windows and doors) disappear and graffiti and neglected buildings present itself. The entrance from Westvest does not attract pedestrians to enter the alley.
Figure 27: Alleys – Poppesteeg (entrance Oude Delft and entrance Westvest)
Consequently, three main conclusions can be drawn from the visual analysis: (i) There are too much barriers (mostly canals, buildings and wide car roads) blocking the natural walking routes pedestrians could use (ii) Bad visibility, poor maintenance buildings and unsafety feelings in narrow / curved alleys (iii) Poor quality of the ground floor facades in the shopping area.
Spatial recommendations and design interventions
After the movements of city tourists, visitors and inhabitants are mapped (‘city use’) and the inner-city is analysed visually (‘quality analysis’) it is time for spatial recommendations or design
interventions. The focus is on areas which do not attract as much pedestrians as desirable and which show one or more problems regarding spatial quality at the same time.
Figure 28: Design intervention “East-West connection” is on city scale
The first intervention is called “East-West connection”, see figure 28. Looking at the history of Delft it seems that the city centre remained the same until the area of Zuidpoort was restructured with underground parking, new stores and dwellings. The city centre expanded towards the south. In other words, when people arrive on Delft Central Station, there is no clear route towards the centre. Despite the fact that east and west have functions as shops and retail not many people visit these areas as can be seen in the previous density maps.
Today Delft has two major new building projects. A new Central Station in the west and a new underground parking garage in the east. These two new changes, either on one side of the city, give a great opportunity to strengthen the east-west direction. The current west side of the city centre contains a program which allows a more intense use of the urban space. The main cause of the low intensity is the lack of an ‘attraction’ like a garage and the fragmented urban space. With the planned development of the new Central Station a new entrance is the ‘attraction’. The east part of the Oude Langendijk is unclear defined. The west part of the Oude Langendijk is a busy shopping street.
However, it suddenly flows into a sort of square with a public transport point. The current program of the buildings surrounding this ‘square’ also does not support the square. Building a bigger bridge would make a nice pedestrian square with the opportunity for lunchrooms, bars and a nice place for boats of the canal tours. The Nieuwe Langendijk can be transformed to an area with the focus on pedestrian movement. The central part of the road, currently used for parking places, should be transformed to a pedestrian area towards the city centre.
Figure 29: Design intervention “Former library area” is on street scale (map and street views - before and after the transformation)
The second intervention is called “Former library area”, see figure 29. This intervention is based on the analysis of pedestrian movements and the places pedestrian stop for a short stay. The places are seen as functions people use. It was discovered that the area around the old library does not function well. Most pedestrians who were followed used the Paradijspoort instead of the
Kruisstraat and functions that are connected to this area are not very often used. So the connection between the Bastiaansplein and the Beestenmarkt is not optimal used. The second problem is that the Kruisstraat and the Achtersack are used as short cuts for cyclists. The proposals consist of a programmatic intervention and a logistic intervention.
At the place of the former library a new building block will appear with a public plinth and apartments on top of it. The functions in the ground floor attract pedestrians to this area of the city centre. The Kruisstraat becomes a pedestrian street without bicycles. The upper part of the Kruisstraat will be connected with the northeast side of the Beestenmarkt. This street becomes the bicycle access road to the north site of the city centre. At the other side of the new street a new housing block is introduced connected to the housing area that surrounds it.
The difference between those two areas is emphasized by giving the living area a green character with trees and small courtyards. The corner of the Molslaan and the Kruisstraat will become a striking point to invite pedestrians into the old library area.
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