How might the built environment be used to support sustainable travel, and how do attitudinal and cultural factors interrelate? How might the theory be applied in practice?
Introduction As concerns surrounding climate change and subsequent natural disasters have become increasingly realistic, so has the importance of addressing these concerns through sustainable measures. By 2040, it is expected that global CO2 concentration levels will reach 450 ppm, resulting in a 78% likelihood of exceeding 2ºC in rising global temperatures (Hickman and Banister, 2014). While this temperature increment may not sound drastic, it contributes significantly to the risk of destructive natural disasters (Hickman and Banister, 2014). Cities have been largely targeted as a starting point from where sustainable measures should be initiated, and rightfully so, as they are responsible for a significant amount of pollution and waste, and are focal points for human activity (Breheny, 1992). Though cities and sustainability are complex bodies with a variety of potential contributors to this field, this paper focuses particularly on the ‘built environment’ and ‘sustainable travel’ at the city level. In particular, how different features of the built environment can be used to support sustainable travel will be analyzed by critically examining compact cities and the low-consumption-city model, the ‘New Urbanism’ concept and transit-oriented planning/development, and the built environment’s Dvariables. Cultural and attitudinal factors will then be considered, studying the role of selfselection in altering the influence of the built environment on sustainable travel. Finally, the city of Dubai, UAE will be considered as a case study and analyzed in relation to theoretical findings.
Body Compact Cities and the Low-Consumption City Model Allowing for variations in variables such as gasoline price, income and vehicle efficiency, Newman and Kenworthy (1989) studied how physical planning policies relate to the conservation of transportation energy by comparing the gasoline consumption in 32 cities globally. In particular, they focused on factors of the built environment: land-use parameters size (population/urban area), density (population/job), and central city strength (proportion of population living in the inner city and average journey-to-work trip length) – and transportation planning factors – use of non-automobile modes (biking/walking), traffic speeds, and availability of parking infrastructure. With similar findings amongst the 32 samples, a unified conclusion was formed. While combining all these factors, it was found that in order to strive towards sustainable travel, better rail transit and more walking/biking are required; as such, the ‘lowconsumption city’ model should be adopted which features low transportation energy, a dense form, a strong center, and intensively utilized suburbs (Newman and Kenworthy, 1989). Using an empirical example to put things into perspective, a comparison is made between the inner areas of New York City and Houston. At the time of publishing, it was found that New York City was a transit-oriented city (64% car use) with a relatively dense inner area (population density: 43.3 persons/acre; job density: 21.5 jobs/acre), and a gasoline production of 335 gallons/capita. In comparison, Houston was found to be an automobile-based city (93% car use) with a lowdensity inner area (population density: 8.5 persons/acre; job density: 10.5 jobs/acre), resulting in a much higher gasoline consumption rate of 567 gallons/capita (Newman and Kenworthy, 1989).
In response, Gordon and Richardson (1989, 1997) rejected the idea of urban
compactness and the low-consumption city model as a whole. While Newman and Kenworthy theoretically tackled the world’s environmental and social issues, Gordon and Richardson responded with a practical and economics-based argument on why applying the suggested
model would not be feasible, without addressing the concerns initially raised, or providing alternative solutions. As a result, most of Gordon and Richardson’s arguments do not relate specifically to the built environment and sustainable travel, however some hold significance to the discussion at hand, and will be focused on further: transit-oriented development/planning and consumer preferences/lifestyle choices (self-selection).
The New Urbanism Movement and Transit-Oriented Development Different time eras have resulted in the formation of different city types. Starting with the ‘walking city’, the arrival of trains and trams then brought about the development of the ‘transit city’ (Newman and Kenworthy, 1996). In both these city types, land-use and transportation were strongly linked, influencing each other heavily. In the 1940’s – mostly in American and Australian cities – the arrival of motor vehicles resulted in the ‘automobile city’ (Newman and Kenworthy, 1996). While the limits of the walking and transit cities were 5km and 30km, respectively, automobiles resulted in developments expanding up to 50km away from the city center, resulting in high levels of decentralization, dispersion and urban sprawl (Newman and Kenworthy, 1996). More importantly, the ‘automobile city’ weakened the transportation-land-use connection as personalized transport meant people could now live anywhere (Newman and Kenworthy, 1996).
Without transportation-related limitations, automobile-dependence and
urban sprawl feed off each other, resulting in obvious and exponential consequences: air pollution, excess noise, and high levels of parking/road-related construction and materials (Newman and Kenworthy, 1996). To counter these car-related problems, a few approaches have been considered, namely: vehicle efficiency, economics and transit-oriented development (Newman and Kenworthy, 1996). Technological advancements (vehicle efficiency) and economics-based measures (fuel taxation/parking charges) both help reduce automobile usage; however, they are unable to
address all the highlighted issues that accompany it. With improved vehicle efficiency, there still remains a need for roads and parking, resulting in obvious consequences; with fuel taxation and parking charges, cars will still be used unless an alternative mode of transport is provided, it will only be more expensive to do so (Newman and Kenworthy, 1996). The
third
approach,
based
on
the
‘New
Urbanism’
concept
and
transit-oriented
planning/development, differs from those previously mentioned in that it tackles all the raised concerns associated with car-dependence (Newman and Kenworthy, 1996). The ‘New Urbanism’ concept aims to link transportation and land-use within cities, improving on their efficiency, equitability, livability and sustainability (Newman and Kenworthy, 1996). Transitoriented developments fit into the ‘New Urbanism’ concept and are a good example of how the built environment might influence sustainable travel. The concept behind these developments is to increase densities surrounding transit stations using the built environment and market forces, resulting in mixed-use development; this will reduce urban sprawl and create sub-centers around the stations (Newman and Kenworthy, 1996). As a result, public transit will become more accessible than in the automobile city, encouraging people to use this more sustainable form of travel. In addition, the mixed-use nature of these developments will encourage other forms of sustainable travel, such as walking and biking to access the station and its surrounding areas.
D-Variables In an effort to further understand the associations between the built environment and travel, Ewing and Cervero (2010) carried out a meta-analysis and arrived at conclusions by summarizing empirical data. As a result, the concepts that were previously discussed in this paper were seemingly splintered and re-assessed, in the form of ‘D-variables’. The Seven Dvariables are: density, diversity, design, destination accessibility, distance to transit, demand management and demographics (Ewing and Cervero, 2010). By analyzing the D-variables in
relation to specific travel outcomes (Vehicle Miles Travelled (VMT), mode choice, trip frequency and trip length), it was found that the relationship between the built environment and travel behavior is inelastic (Ewing and Cervero, 2010). However, it can still be concluded that by combining different D-variables, the built environment can substantially influence travel outcomes (Ewing and Cervero, 2010). Finally, contrary to findings by Cao, Mokhtarian, et al (2009), it was found that by controlling self-selection, the influence of the built environment on travel behavior was not affected (Ewing and Cervero, 2010). Therefore, Ewing and Cervero (2010) have found that self-selection does not have a significant effect on how the built environment influences travel behavior. As such, we will look at this point in more detail, and further examine the role of self-selection (cultural and attitudinal factors) in relation to the built environment and travel behavior.
Self-Selection and Cultural and Attitudinal Factors Through findings in the studies previously mentioned in this paper, it can be concluded that the built environment can in fact have a strong influence on travel behavior; however, to form a realistic image, the incorporation of self-selection must be thoroughly considered as it can potentially alter this influence. Cao, Mokhtarian, et al (2009) focused on empirical data from different studies to understand the extent to which self-selection affected the influence of the built environment on travel behavior. Results from 38 studies based on 9 different approaches have shown that the built environment does in fact have an influence on travel behavior once self-selection is accounted for; however, they have also shown that this influence does decrease considerably as a result of self-selection (Cao, Mokhtarian, et al, 2009).
It is yet to be
concluded which of the two has a stronger autonomous influence on travel behavior; however, it is important that both are considered simultaneously, as analyzing the built environment without accounting for self-selection could result in misdirected land-use policies and an overestimation of their true impacts (Cao, Mokhtarian, et al, 2009).
Case Study In order to understand how this theory can be applied in practice, and to put the theories discussed in this paper into perspective, Dubai (UAE) will be adopted as a case study. Dubai started to develop its urban infrastructure (including roads and transportation networks) upon the discovery of oil in 1966 (Government of Dubai, 2014). Today, Dubai’s urban structure is composed mainly of a one high-speed motorway (Sheikh Zayed Road) along which dense, mixed-use developments have formed. Further away from the motorway, less dense, mostly single-use developments can be found, as well as other less prominent high-speed motorways. Traditionally, Dubai was an automobile-based city with limited public transport facilities. Though it is uncertain when the public bus system started running, the main public transit facility – the Dubai Metro – was introduced in 2009 (Dubai Metro, 2014). Initially running on one line, a second line was introduced in 2011, with additional lines planned to be introduced in the future (Railway Technology, 2014). With two operational Metro lines, one of which services the main high-density motorway (Sheikh Zayed Road), the Dubai Tram was introduced in 2014 to serve as a feeder to the Metro and enhance the public transit system by integrating the residential, lower-density and single-use developments into the network (Dubai Metro, 2014). In order to examine the influence of the built environment on sustainable travel in Dubai, and how cultural and attitudinal factors interrelate, some statistical figures will be analyzed. While the Metro was introduced in 2009, the statistical analysis will focus mainly on the 2011-2013 period, in order to have allowed some time for the project to start taking effect. Public Transport The annual Dubai Metro ridership increased from 6.9 million passengers in 2009, to 138 million in 2013, including a 30 million jump (2010-2011) with the introduction of the second line (Dubai Statistics Center, 2014). Prior to the introduction of public transit, taxis were generally used as a
means of transport for people without personal automobiles; between 2011 and 2013, while the number of taxis available increased from 7,942 to 8,702, the number of trips declined by almost 10 million (91.5 million trips in 2011 to 81.6 million in 2013) (Dubai Statistics Center, 2014). In addition, as the number of buses and available bus routes increased, the public bus ridership increased from 107,408 passengers in 2011, to 115,676 passengers in 2013 (Dubai Statistics Center, 2014). Automobiles On the contrary, although no information was found relating to VMT or gasoline consumption in Dubai, the number of light vehicles registered increased from 925,013 in 2011, to 1.1 million in 2013 (Dubai Statistics Center, 2014). However, the number of speeding violations decreased from 1.52 million violations in 2011, to 1.25 million in 2013, hitting a low of 1 million in 2012 (Dubai Statistics Center, 2014). Population General population trends have been increasing since the establishment of Dubai. In particular, for the time frame included in this analysis, there was a population increase from 2 million in 2011, to 2.21 million in 2013 (Dubai Statistics Center, 2014). Findings What can be concluded from analyzing this case study is that both the built environment and self-selection play important roles in influencing sustainable travel. With a relatively good landuse system already in place, improving the built environment by adding a strong public transit system resulted in positive movement towards sustainable travel in Dubai. The ridership of the Dubai Metro has increased steadily, the number of taxi trips (formerly a substitute for public transit) has decreased dramatically, and the number of speed-related traffic violations has also
decreased; all of which are signs that point towards more sustainable travel. Although no direct measure of car usage was found (VMT/gasoline consumption), the number of light vehicles registered has been increasing, meaning Dubai is still relatively car-dependent. This can be explained with a few points: 1. Limited access to Metro facilities: main metro line serves the prominent Dubai motorway (Sheikh Zayed Road), making it harder for areas further away to access the service; 2. Self-selection: Dubai is historically an automobile-based city, meaning people are culturally more accustomed to the use of automobiles, and their attitudes are potentially ‘locked-in’ to personalized transport as a result; 3. Any new intervention requires ‘time to breathe’ before taking full effect; 4. Steadily increasing population. With the newly introduced Dubai Tram, a feeder to the Dubai Metro that is expected to integrate the currently lesser connected areas into the transit system, it is expected that Dubai will become more dependent on public transit and less on automobiles, thus advocating sustainable travel and reducing the environmental/social consequences accompanying the automobile city.
Conclusion Through studying different findings published over the last quarter century, conclusions have been drawn regarding the influence of the built environment on sustainable travel and how cultural and attitudinal factors interrelate. Dubai, UAE was adopted as a case study, and the application of the theoretical findings were analyzed in a practical sense. The main findings are that the built environment and self-selection (cultural and attitudinal factors) both have a significant influence on sustainable travel, and while it cannot be concluded which has a greater impact, it is imperative that they are not considered autonomously. A few important lessons can be extracted from the process of preparing this paper. Firstly, moving towards sustainable travel is a complex transition with both tangible and intangible features, all of which need to be jointly considered and coordinated to achieve a desirable outcome. Secondly, by zooming out of the
scope of this paper and looking at the ‘bigger picture’, the lessons taken can be translated to a wider spectrum. For example, much like self-selection plays an ‘intangible’ role in affecting how the built environment can influence sustainable travel, factors such as regional neighborhood location (Handy, 2006), population demographic and environmental awareness are examples of others, both tangible and intangible, that could substantially impact this influence. Finally, given the earth’s worsening condition and the pending consequences of a business-as-usual approach, any interventions that can alter the built environment in pushing forward sustainable travel should be seriously considered.
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