Urban Transportation Problems - Assignment Example

Urban Transportation Problems How does the new tendency toward mixed use, new urbanism development techniques tend to complicate and undermine theaccuracy of traditional trip generation and traffic projection/modeling techniques? What can be done to counteract and offset these problems? Mixed use, new urbanism development is a characteristic of smart growth planning and contemporary land use techniques, the aim of which is to reduce the dominant use of private automobiles and encourage walking or biking. The idea is to put offices, shops, restaurants, residences, and similar such activities close to each other and to residences, so that the shorter trip changes from what should have been an external trip by motor vehicle, to an internal walk, bike, or transit trip (Feldman, Ewing & Walters, 2010). Because the mixed use configuration is essentially internal and encourages pedestrian and non-automobile transportation methods, the forecasting of traffic patterns through trip generation and traffic projection utilised by practitioners tended to be similar to each other. The Institute of Transportation Engineers (ITE) have formulated a method by which trip generation can be performed. Feldman, Ewing and Walters (2010) describe the procedure in the following steps: The analyst gathers information about the amounts and kinds of different land uses (e.g. residential, office, commercial retail) that are present in the area for development; The estimated figures are then multiplied by a set of per-unit trip generation rates that ITE has developed, to get a preliminary estimate of the number of vehicle trips that are generated by the site; The initial estimates of generated trips are then lowered by a certain percentage, based on lookup tables by the ITE. The reduction represents the internal capture of trips in the mixed use development. The share of internal trips as shown in the look-up table is multiplied by the total number of trips for each of the different uses, to arrive at a first estimate of internal trips for each use. For each pair of uses (production and attraction, or source and destination use) are reconciled, so that the number of internal trips produced by one use is equal to the number of trips attracted by the other use. The lower of the two estimates of internal trips is the limitation of the number of internal trips created by the other use (Feldman, Ewing & Walters, 2010). The traditional trip generation method developed by the ITE has some advantages when applied to mixed-use development areas. First, the process appears to be objective, because if two different analysts worked on the same data, they will arrive at the same result. The steps used for calculation are specific and do not allow for deviation. Secondly, the procedure appears logical, because productions (where the trip originates) and attractions (where the trip is destined for) appear matched for each trip purpose, so most analysts and engineers easily accept that the degree of internalization can be determined from these relationships. Thirdly, the method is fast and straightforward, and an analyst can easily develop a spreadsheet template where he can input the data, and produce an answer almost instantaneously (Feldman, Ewing & Walters, 2010). On the other hand, there are some weaknesses that the method poses when it is applied to the mixed use development project. Feldman, Ewing & Walters (2010, p. 3) lists these shortcomings as follows: The traditional method makes use of two look-up tables prepared by the ITE. The table figures were, however, were based on a set of data based on three sites analyzed by the Florida Department of Transportation (ITE Trip Generation Handbook, 2004, p. 130). Since the accuracy of the forecasts depend upon the accuracy of the table figures, the correctness of the estimates will depend upon how closely the figures in the table approximate the actual site being studied, which of course is not necessarily Florida. There may be instances when the error introduced between the table figures and the actual figures is substantial. The look-up table is limited in that it provides values for only three uses, namely residential, retail and offices. Any uses other than these that are present in the mixed use area cannot be assessed for their traffic impact on the model. The method disregards the scale of development of the mixed use area. If the site were large with many productions and attractions, there will certainly be more “matches” than those present for small sites. In the look-up tables, therefore, large sites will produce higher cell percentages than those for small sites. A distortion based on the scale of development is therefore introduced. The traditional method of trip generation or traffic modelling ignores the land use context for development projects. It is only normal to expect that projects that are found in remote locations will more likely capture trips that are on-site than those captured by projects that are more closely located to other attractions, and which therefore experience a lower capture rate to the external destinations. The traditional trip generation method likewise fails to take into account the possibility that there may be significant shifts or changes in modes of travel, especially for well-integrated and transit-served sites (Feldman, Ewing & Walters, 2010). To illustrate this last point, consider the following conceptual framework of the mixed-use development model. The nature of the different choices is apparent, as to destination as well as to mode of travel. The D variables refer to the familiar “D” elements, including the “three Ds” suggested by Cervero and Kockelman (1997, in Feldman et al. 2010), namely density, diversity and design. Four additional Ds suggested by other authors include destination accessibility, distance to transit, and demographics, suggested by Ewing and Cervero (2001), and development scale, suggested by Feldman et al., 2010). The variety of choices among destinations and modes complicates the traffic projections and trip generation model for mixed use development. Source: Feldman, Ewing & Walters, 2010, p. 3 There are several practical means by which these problems in the application of the traditional method of traffic projection to mixed use projects may be addressed. ITE’s Trip Generation Handbook itself proposes some of these. Firstly, it is necessary to consult with experts on the matter of traffic modelling, in order to solicit reliable advice based on the particular conditions in the project being evaluated. Secondly, the application should be done on a case to case basis. It is misleading to conceive of the traditional method as an error-free, fail safe system, because of the simplicity and straightforwardness of its procedure. Adjustments may be required based on the particular case under consideration. Thirdly, consultations may be necessary on those uses for which the ITE tables do not provide the necessary information. It must be recalled that table values are provided only for residential, retail and offices, therefore for mixed uses involving restaurant, theatre, and other commercial uses, actual onsite evaluation by a qualified traffic engineer or planner may be necessary. 2. Describe how a context sensitive, complete streets transportation system can counteract the impacts of a sprawl development pattern. What are the limitations of retroactively applying such a system to an already sprawling urban community? The complete streets policy seeks to ensure that future road projects in a community take into consideration the various requirements of all users, from all age groups, of different abilities, and using non-automotive means of mobility (such as pedestrians and bicyclists, in particular). Typically, complete streets have allocations for sidewalks, bicycle paths, bus stops placed at convenient locations, median islands, frequent crosswalks, and pedestrian traffic signals (Ernst & Shoup, 2009, p.9), although the particulars may vary from place to place. Furthermore, a design is context-sensitive when it requires that part of the input to a design would be considerations about the environmental impact, ensuring that the engineering design does not result in endangerment to the ecology (Amekudzi & Meyer, 2005, p. 13). On the other hand, urban sprawl is defined in architecture as any unplanned development of open land, usually located on the outskirts of a city. It is characterised by low-density development, distance from employment centers and commercial establishments. Because urban sprawl is a spontaneous development that did not rely on planning, it is relatively incoherent, with land use choices made by many different personal decisions. Sprawl is considered costly in that the relatively low density population is still allocated government funds for the building of roads, sewers, and basic services, which is usually subsidized by non-users. There are negative effects associated with sprawl, such as air pollution, water pollution, and other implications on the use of automobiles; because sprawl is remotely located, and less frequented by transit systems, it necessitates a significantly greater use of automobile transportation. Therefore, sprawl is also associated with higher travelling speeds, fewer sidewalks, absence of crosswalks, and consequently a higher rate of pedestrian accidents involving particularly children and the elderly. Sprawl also impacts on the elderly and those who are unable to access automobile transport, meaning that there is less access also to medical care, social services, shopping for necessities, particularly where mass transit is unavailable (Surface Transportation Policy Project, 2000). Part of the attributes of sprawl is the inefficient street layouts, which is a sign of the lack of planning and high degree of individual personal decisions. It is therefore possible that the institutionalisation of a context sensitive, complete streets transportation system may lessen or counteract the effect of sprawl. A complete streets and context sensitive system will immediately assure pedestrians of a much greater degree of safety than can be encountered in the typical roads in sprawl. Existence of pedestrian lanes and crosswalks, as well as speed humps and elevated islands, provide pedestrians additional protection when crossing the road. The mere availability of safe avenues for pedestrians would encourage people to walk to nearby destinations, and conversely, more commercial establishments will be encouraged to set up shop in sprawl communities because of accessibility to its markets. The result is a reduction in the use of automobile, which in turn causes a drop in car emissions and eventually, lower air and water pollution. This in turn should result in an improvement in health conditions of the citizens. There will be greater difficulty in trying to apply a context sensitive complete streets transportation system in the area with advanced sprawl characteristics. Complete streets may require a wider use of land than is available, because of allocations of parking, sidewalks, and crosswalks. Likewise, the unplanned allocation of land according to use makes it difficult to allocate for design features such as a wider sidewalk for commercial areas where pedestrians would tend to gather in front of entrances/exits and to look at the display window. Another possible drawback would be the existence of local legislation affecting land use or the setting up of additional infrastructure. However, it is not difficult to the point of being impossible, as most arterial roads in sprawl may be converted to more pedestrian and bicycle-friendly thoroughfares. It would be relevant at this point to mention the relatively recent paradigm known as emergent urbanism. Emergence proceeds on the principle that urban “planners” are seldom presented with the opportunity to design cities from bare earth. Most of the time, a community is already existent, a thriving thing that is more analogous to a biological entity than an engineering or physical project, because it presents complexities to its transformation. The introduction of complete streets design to a community with advanced sprawl is one such dilemma. In a way, emergence is the opposite of design (Helie, 2007), in that it commences in the midst of a situation already existing, and instituting the desired change in such a way as to minimize any disruption or displacement in the existing community. In advanced urban sprawl, roads tend to be built for fast driving with all obstacles cleared away (Helie, 2008). This is in direct contrast to the complete streets concept that not only allows but encourages non-automotive mobility. A change of attitude among the residents must likewise be engendered by the designers, together with a change of street design and construction, or maybe through it, which will require a study of the complexities of the way of life of residents in the area. References Amekudzi, A & Meyer, M 2005 “Consideration of Environmental Factors in Transportation Systems Planning”, National Cooperative Highway Research Program Report 541, Transportation Research Board, Washington D.C. Ernst, M & Shoup, L 2009 Dangerous by Design: Solving the Epidemic of Preventable Pedestrian Deaths (And Making Great Neighborhoods). Surface Transportation Policy Partnership and Transportation for America. Federal Highway Administration (FHWA) 2006 University Course on Bicycle and Pedestrian Transportation. Publication No. FHWA-HRT-05-133, July 2006. Turner-Fairbank Highway Research Center, McLean, VA. Feldman, M; Ewing, R; & Walters, J 2010 Evidence of Mixed-Use Trip Generation – Local Validation of the National Survey. Accessed 2 November 2010 from www.westernite.org/annualmeetings/.../ITE%20Paper_5B-Feldman.pdf Helie, M 2007 Emerging the City. Emerging Urbanism: Rediscovering Urban Complexity. 18 October 2007. Accessed 2 November 2010 from http://emergenturbanism.com/2007/10/18/emerging-the-city/ Helie, M 2008 Producing land with nested markets. Emergent Urbanism: Rediscovering Urban Complexity. 30 November 2008. Accessed 2 November 2010 from http://emergenturbanism.com/2008/11/30/producing-land-with-nested-markets/ Institute of Transportation Engineers (ITE) 2006 Context sensitive solutions in designing major urban thoroughfare for walkable communities. Institute of Transportation Engineers, Washington D.C. New Urbanism site. 2010 Principles of Urbanism. Accessed 7 November 2010 from http://www.newurbanism.org/newurbanism/principles.html Surface Transportation Policy Project (2000). Mean Streets 2000: Pedestrian, Health, and Federal Transportation Spending. Washington, DC. Read More