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Yet Another Urban Blog

~ Yoav Lerman's Blog

Yet Another Urban Blog

Category Archives: Tel Aviv

Pedestrian Movement and the Built Environment in One Simple Diagram

28 Wednesday Oct 2015

Posted by Lerman in Academia, Israel, Land-Use, Tel Aviv, Transportation

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Space Syntax; Bill Hillier

Following the previous post which discussed actual observed pedestrian movement and commercial streets in Tel Aviv, we now turn to the major theoretical contribution we made in our last paper regarding the connection between the built environment and pedestrian movement.

In order to understand the connection between pedestrians and urban environment we have quantified a lot of built environment features. Those variables were divided into four different dimensions:

  1. A spatial dimension. This dimension is related to the structure of the road network, meaning the basic urban space mainly consisting of streets and squares. This dimension of the built environment is relatively stable and does not change. Various studies have already shown the importance of the street network configuration to pedestrian movement as well as other urban dynamics.
  2. A functional dimension. This dimension relates to land use and we included in it the distribution of retail fronts and proximity to public transit.
  3. A physical dimension. This dimension is related to actual street sections, meaning the width of the sidewalk and carriageway, which determines how easily a pedestrian can cross a street.
  4. A demographic dimension. This dimension is related to residential and employment densities.

While conducting this study I have spent numerous hours doing field surveys to map all kinds of missing data. Specifically, retail fronts locations as well as road and pavement widths are not easy to come by. As the age of Big and Open Data is fast approaching I hope that more types of data will be collected on a regular basis, leaving us with more time for analysis. After we have collected all the quantitative data we ran endless statistical correlations to better understand how the built environment and movement are tied together. The conclusions below are derived from the statistical connections we found.

Our study draws heavily on space syntax theory, which emphasizes the dominance of the street network structure on various urban dynamics. One of the best known papers in this field deals with the connection between urban space and pedesrtian movement. This paper from 1993, written by Bill Hillier and others describes the natural movement of people in urban space and connects movement, land use and street network structure.

Hillier offers the following diagram as a description of the interaction between movement and the spatial and functional dimensions. Hillier presents the argument that the spatial configuration is the basis of urban processes. He shows that the configuration can impact both movement and land use, but land use and movement cannot impact the spatial configuration. Movement and land use have a reciprocal connection, meaning that movement may induce retail development and that retail may in turn impact movement in its area. In the diagram below movement is marked with M, retail is marked with A (for attraction) and street network is marked with C (for configuration):

Hillier et al. (1993) pedestrian movement diagram

Original Hillier

Our findings are in line with Hillier’s diagram. Our theoretical contribution is an extension of Hillier’s diagram to include the physical dimension and add the urban area type (traditional vs.contemporary) as the basis of the generation of urban space itself.  The physical dimension was found to be impacted by the configuration and to have an impact on movement (similar to the functional dimension). Essentially, sidewalk width may change due to people movement and in turn change the movement pattern. In the diagram below you can see Hillier’s original triangle to the right and at the the top is the urban area type which impacts all the urban environment dimensions.

Lerman and Omer (2016) pedestrian movement diagram

DiagramForBlog

The next post will deal with specific finding and the struggle to find the best movement model for every city.

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Where People Go and Commercial Streets Grow

26 Monday Oct 2015

Posted by Lerman in Academia, Israel, Land-Use, Planning, Tel Aviv, Transportation

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Commerce

The next few posts will be dedicated to my PhD dissertation dealing with pedestrian movement in different urban contexts. The paper containing my dissertation’s major findings has been accepted for publication in the journal – “Computers, Environment and Urban Systems” – and for a limited time is available for free. The paper was written together with my advisor, Itzhak Omer, under the title:

Urban Area Types and Spatial Distribution of Pedestrians: Lessons from Tel Aviv

Essentially, this study aims to examine what conditions lead to greater pedestrian movement in urban space. To achieve this goal we have quantified various attributes of the built environment and then checked their statistical association with the level of observed pedestrian movement. The research was carried in four different areas in the city of Tel Aviv. Each of those areas was split into a traditional urban area and a contemporary one, reflecting the major shift that occurred during the 20th century in urban planning from a humanistic discipline to a technocratic one. In this sense Tel Aviv is an ideal case for such an investigation containing both contemporary and traditional urban areas in close proximity.

This post will focus on the observed pedestrian movement volume and the retail fronts distribution. First, let’s have a look at the chosen research areas and their division to traditional and contemporary urban areas. The map below shows the research areas in the context of the city of Tel Aviv (click to enlarge):

ResearchZones

The close up aerial photos below show clearly the differences in the street network between the traditional connected areas to the contemporary less connected areas:

The first area (marked with the number) is centered on Ibn Gabirol Street, which is one of the major commercial streets in the city. The second area comprises of Florentine Neighborhood. In these areas both the traditional and contemporary parts were planned, yet they differ significantly in the connectivity levels and in land use composition. In both cases the contemporary area is a super-grid of the older traditional area next to it. In addition, Florentine’s contemporary area was planned as an industrial area and as a result have a rather low residential density.

The third area comprises of the neighborhoods of Hatikvah (traditional) and Yad Eliyahu (contemporary), while the fourth area is made of the neighborhoods of Shapira (traditional) and Kiriyat Shalom (contemporary). In both of these case the traditional neighborhoods were unplanned in some sense and had a bottom-up process of generation. In contrast, both of their contemporary counterparts were planned from the top in the fashion of early modernistic planning after the second world war.

The following map shows our findings regarding observed pedestrian movement volume and retail fronts distribution in all of the research areas. The pedestrian movement volume is distributed in a heavy-tailed way, meaning that there are only a few streets that carry a lot of movement while most of the streets carry low movement volumes. To visualize this we have emphasized the points where the top 10% of pedestrian movement was observed with red points and the next 20% are highlighted using orange points. In this context, heavy pedestrian movement means over 400 pedestrian per hour and medium movement rate means stands for over 200 pedestrians per hour. As for retail distribution – streets sections in which both sides have retail are marked with red lines, while streets with only one side of retails are marked with orange lines.

PedestrianCountAndRetail

Basically, the traditional areas have a more connected street network, with a higher presence of retail fronts and a higher volume of pedestrian movement. Moreover, even in the traditional sub-area where the lowest pedestrian movement volume was observed (which is Shapira Neighborhood in the top of area number 4), the average movement volume per road segment was higher still than that in the contemporary sub-area with the highest pedestrian movement volume (which is the eastern Ibn Gabirol area – to the right of area number 1). Pedestrian movement is higher in that traditional area even though the residential and employment densities are lower than that of the contemporary sub-area.

It can be clearly seen that in all traditional urban area commercial streets have successfully developed, while in the contemporary urban areas no commercial streets managed to grow. This happened regardless of municipal regulations that sometimes tries to prohibit commercial development and at other times tries to promote it. The commercial streets have all developed along the most central streets. Over the fine grid of Florentine (top-right in area number 2) an extensive grid of commercials street had sprouted from the top-right intersection, which is a rather central intersection in the city of Tel Aviv.

In conclusion, urban commerce does not happen based on an abstract will of a planner, but is the result of certain conditions, where the most important aspect is the road network, its intensity and the centrality it provides to certain streets. The next post will deal with the statistical associations themselves between commerce, street centrality and pedestrian movement. In addition, these findings are in line with other studies on the growth of urban commercial activity. Recommended reading on this subject include the following papers, which are free to access:

“The effects of block size and form in North American and Australian city centres” by Arnis Siskna. This paper examines 12 CBDs of North-American and Australian cities and reaches findings on land use formation based on the street network and morphological structure. Siskna points to the spontaneous development of urban commerce in the shape of a spiky potato.

Another and better known paper extends Siskna’s findings: “Centrality as a process: accounting for attraction inequalities in deformed grids” by Bill Hillier. In this paper Hillier suggests several insights regarding the development of intense urban centers and the needed conditions for them.

And as previously mentioned, you can find my new paper which further confirms and extends on Hillier’s work here.

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Planning Committee Sinks Apartment Tower into Groundwater in Tel Aviv

23 Thursday Apr 2015

Posted by Lerman in Criticism, Housing, Israel, Parking, Planning, Tel Aviv

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Arlozorov Towers, Young Towers

Tel Aviv, the financial center of Israel, is notoriously known for its housing shortage and rapidly rising prices (some of it due to the incompetent Israel planning regime). On more than one occasion it seems as if the regulations have been put in place to insure chronic housing shortage. Building anything next to something else is almost impossible, while creating new cheap apartments in centrally located areas belongs to the realm of science fiction.

Last week gave us just such as an example in a project called the Young Towers (although nobody living today will be young when they are completed). This project consists of two towers of over 40 floors each (video visualization here), under construction right next to the corner of Arlozorov Street and Begin Road (named after the late Israel PM Menachem Begin and not related to any actual beginnings). Although the project is located in the commercial center of the metro area next to the largest train station in Israel and with plenty of public transit access, the authorities made the developer build six underground floors (!) for car housing parking. Digging that deep the developers had not reached molten lava, but did hit the groundwater sucking money and time out of the project. Even a special Dutch expert brought in to address the issue (and who knows better than the Dutch how to keep the sea dry) could not handle the situation. This is a photo taken from this article (in Hebrew) describing the boondoggle that the project got drowned in:

Groundwater stops construction of an extensive underground parking lot. (source)
Apartment Blockers in Tel Aviv

This shows Israeli planning at its current worst and resembles many situations in places that are not as backward as Tel Aviv. The main priority of planning committees in Israel lies in providing cheap accommodation for cars, while every other objective (housing, schools and so forth) gets pushed back. Israel has planning regulations that dictate the provision of at least one off-street parking spot for each new residential unit, while completely ignoring the size of the new unit and its location. On top of this policy directive, municipalities tend to provide free on-street parking at all times, leading many underground lots to be underused as people keep searching for free spots above ground.

Alan Durning from the Sightline Institute composed an eye-opening post on such mandatory parking lots in Seattle, which he termed “Apartment Blockers” due to the cost and time they add to the construction of new housing units, and the fact that these requirements lead to reductions in the amount of housing units a developer is allowed to build:

City requirements for off-street parking spaces jack up rents. They jack it up a lot at the bottom of the housing ladder. Proportionally speaking, the bigger the quota and the smaller the apartment, the larger the rent hike. For one-bedroom apartments with two parking places, as is required in places including Bothell and Federal Way, Washington, as much as one-third of the rent may actually pay for parking. A flotilla of studies supports that claim, and I’ll summarize them in this article, but first, a case study of residential real estate development may illuminate how critical parking is to the affordability of housing.

While Tel Aviv may be a little bit behind regarding rational urban development it’s surprising that even urban role models such as Portland, Oregon have the same stupid rules. We can take some comfort in the fact that more people are aware that “free” parking is anything but free, and that parking is, in fact, not a public good. Even the city of Mumbai has finally started to charge a fee for on-street parking.

Tel Aviv should learn the obvious lesson from this groundwater case and start focusing its planning priorities on those among us who really need central and affordable housing – humans.

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