Chapter 6 Road Collisions and Urban Development
6.4 Effective Land Use Planning
6.4.2 Land Use Planning Risks
One of the most contentious issues surrounding land use planning and road colli- sions is traffic flow. This is a consequence of the land use planning itself and has a direct and indirect impact of the volume and nature of road collisions. Little has been researched on road collisions and traffic flow, for a number of reasons, largely data.
Accurate data are limited only to large cities, and then it can be difficult to aggregate.
Traffic flow is largely linked to speed, which often means that when traffic flow is slow, the likelihood of an injury collision is low. However, when traffic flow is fluid, the speeds are higher and likelihood of collision risk is higher.
Generally speaking, studies of relationships between collisions and traffic flow can be divided into two types: (a) aggregate studies, in which units of analysis repre- sent counts of collisions or collision rates for specific time periods (typically months or years) and for specific spaces (specific roads or networks), and traffic flow is rep- resented by parameters of the statistical distributions of traffic flow for similar time and space; and (b) disaggregate analysis, in which the units of analysis are the colli- sions themselves, and traffic flow is represented by parameters of the traffic flow at the time and place of each collision. Disaggregate studies are relatively new and are made possible by the proliferation of data being collected in support of intelligent
transportation systems developments. Transportation management centers routinely archive traffic flow data from sensor devices such as inductive loop detectors, and these data can, in principle, be matched to the times and places of collisions.
Traffic congestion and road collisions are two important externalities created by road users. Increased travel time caused by traffic congestion imposes costs to road users, both in terms of economic loss and also the reduced quality of life and mobil- ity. The costs of road traffic collisions to individuals, property, and society in general have also been significant. Traffic congestion and collisions both impose a burden to society, and as such it is important to reduce their impacts. An ideal solution would be to reduce them simultaneously but this may not be possible; however, it is specu- lated that there may be an inverse relationship between traffic congestion and road collisions (Shefer and Rietveld 1997). Shefer and Rietveld (1997) hypothesize that in a less congested road network, the average speed of traffic would be normally high, which is likely to result in more serious injuries or fatalities. On the other hand, in a congested road network, traffic would be slower and may cause less fatalities and serious injuries. This increased traffic congestion may lead to more collisions due to increased traffic volume; however, those collisions may be less severe. This suggests that the total external cost of collisions may be less in a congested situation relative to an uncongested situation. This poses a potential dilemma for transport policy makers since it would appear that traffic congestion can improve road safety; however, traffic congestion reduces mobility, which subsequently decreases economic productivity.
Land use is a principal determinant when making trips and is the main influ- encing factor for road-based environments and its related variables including traffic flows, speed limits, and pedestrian activities (Lupton et al. 1999). According to urban safety management theory, land use policy is one of the strategies used to prevent and reduce road collisions (The Institution of Highways and Transportation 1997).
Different types of land use generate different types of trips and encourage different types of driver behavior, which in turn can lead to the potential of a road collision.
If we take a wider perspective, many other aspects of road collision analysis are also associated with different land uses and associated activities.
Noland and Quddus (2005) reiterates the issue that although congestion (and reduced traffic flow) leads to more collisions, these collisions are less severe. However, they point out that this poses a policy dilemma for decision makers. As Noland and Quddus (2005, 738) summarizes, “[e]xternal costs associated with congestion may be off-set by external benefits associated with fewer traffic fatalities due to conges- tion.” Noland’s study of congestion and road safety in London found inconclusive results, speculating that the speeds are generally low in both inner and outer London, and those areas are congested already and have infrastructure already in place, which mitigates the safety effects of high-speed traffic (Noland and Quddus 2005).
Special mention must be given to China with regard to land use, road collisions, and increasing urban population. Rapid motorization in China especially private cars increases about 15%–20% each year. This increase creates undesirable environ- mental and social problems. In China, there are 160 cities with a population over one million; it is safe to say land use and rapid urbanization followed by motorization has a large role to play in the increasing number of road collisions. According to official studies, there are about 450,000 car collisions on Chinese roads each year, which
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cause about 470,000 injuries and 100,000 deaths. The total cost of these collisions was 2.4 billion dollars. The study concluded that 92% of these collisions were due to bad driving skills. These figures are disputed by a WHO study, which reported that the actual number of fatalities on China’s roads is more than twice the official figure, or about 250,000 killed each year. This study estimates that 45,000 people are injured and 680 killed on China’s roads each day. Road traffic collisions are believed to be the leading cause of death for people 15–45 years old. The direct and indirect costs of these collisions are estimated at between 12 and 21 billion dollars, or about 1.5% of China’s GNP. This collision rate means that roughly 20% of the world’s fatal car collisions take place in China (Zhang et al. 2008).
One of the major issues for China is the speed of urbanization and land use plan- ning, residential and associated amenities are car-centric, building on the U.S. style of car-based infrastructure. With the increasing number of individual vehicles, road space and traffic control measures cannot keep up; the result is traffic congestion, safety, and parking problems. Although the rapid conversion of land from rural to urban areas is mostly due to financial incentives, it provides more transport infra- structure opportunities, which could indirectly increase the demand for automobiles.
In turn, higher demand for automobiles could also result in suburban development, leading to long-term urban sprawl in low-density regions accessible only by individ- ual vehicles, as public transport cannot afford to provide service when densities are low. Providing gasoline for private cars and mopeds and diesel for trucks also leads to rising air pollution as well as increasing greenhouse gas emissions.
Since motorization began to increase some two decades ago, road safety has been recognized as a major issue in China. During the period from 1975 to 1998, traffic fatalities increased 243% (Kopits and Cropper 2005). Currently, road collisions in China account for about 300 deaths per day (CRTAS 2006). The increase in the number of automobiles is one of the main factors contributing to the increase in traf- fic fatalities. Even with relatively low specific motorization rates, China already had 104,372 road-collision-related deaths in 2003. Put in perspective, the U.S., with about six times the number of motor vehicles (three if two-wheelers/mopeds are counted), has only 45% as many fatalities. Both the high number of pedestrians/cycles/two- wheelers as “targets” and poor safety per se account for this huge difference in collisions per vehicle, which would be even starker if the greater distances/vehicle characterizing the U.S. over China were used in the comparison.
The WHO estimates that 1.2 million people are killed in traffic collisions globally every year (Peden et al. 2004), implying that almost 3300 people are killed every day, of which approximately 10% occurred in China. The significant number of traf- fic fatalities in China is most likely to be caused by the sudden increase in motor vehicles in dense urban areas with infrastructure principally built for nonmotorized transport users. Moreover, the increase in the inflow of people from rural to urban areas could also result in the high fatality rate, as people are still adapting to the relatively new and rapidly developing city traffic flows.
Rapid motorization often leads to inequities in transport mobility and accessibil- ity. Motor vehicles have clearly benefited people who can afford to own private cars, but traveling conditions for pedestrians and cyclists have deteriorated over the past few decades, mainly due to the significant reductions in sidewalks and bike lanes.
Benefits, therefore, to a proportion of society have come at a high cost to the major- ity, as cars have invaded the space of others. Problems caused by such changes have not been solved, nor have government authorities started looking into these issues yet. Numerous reports across major Chinese cities—including Beijing, Shanghai, Shenzhen, Nanjing, Fuzhou, Guangzhou, Hangzhou, and Shenyang—describe the takeover of pavements and bike lanes by motor lanes, and subsequent public dissatisfaction with these developments. As these reports on road-space distribution suggest, the integration of social issues in current transport planning is generally lacking. Currently, there is no legal regulation that forbids motor vehicles to travel on traffic lanes not specifically designed for their usage. Motor vehicles generally have the right-of-way, which cyclists and pedestrians find threatening. Bike-free streets in Beijing first appeared in the late 1990s, and Shanghai urban transport officials were known to project the role of bus transit as a replacement for walking. Rapid motorization in China presents individuals and authorities with a daunting challenge.
Chinese car penetration is well below 100/1000 people, except in Beijing and a few other coastal cities. In a sense, it threatens to play the role of the third scenario in the original work used for the present scenarios, which was called “car collapse.” What car collapse—gridlock in major Chinese cities—threatens to do is to deprive China and its people of the true benefits of individual motorization and the utility of owning cars. If that were to push China’s automobile industry itself off the road to healthy growth and success, the costs would be very high. Many of the social problems asso- ciated with motorization could be mitigated if there were more time. The speed at which cars became popular in Beijing, however, suggests there is not much time.
Wedagama et al. (2006) investigated the relationship between pedestrian injuries and certain land use types, for example, retail, offices, leisure, and junction density, on weekdays and weekends. Furthermore, the analysis intended to derive a relation- ship between different land use types or trip attractors and temporal variation of pedestrian and cyclist injuries. However, the analysis by Wedagama et al. (2006) did not disaggregate the pedestrians by age. Graham et al. (2005) investigated the influ- ence of area deprivation on child and adult pedestrian injuries, considering England as a case study. This study concludes that the residential areas are likely to be safer for children than mixed use areas in inner cities.
The issue of land use and road collisions has often been focused on pedestrians and cyclists. In the U.S., pedestrians are the second largest population group to die in motor-vehicle-related collisions (LaScala et al. 2000). In the United Kingdom, The House of Commons Transport Committee (1996) examined ways to reduce risk to pedestrians and cyclists. In addition, the Department for Transport (DfT) is promot- ing a modal shift to walking and cycling for shorter journeys and aims to make these modes safer. An increasing degree of urbanization is associated with an increase in nonmotorized transport injuries through demographic factors (e.g., population den- sity) and road and traffic environment factors such as road length, junction density, and land use. For instance, the risk of a pedestrian collision is up to five times greater for children living in urban areas than for those living in rural settlements (Petch and Henson 2000).
A few previous studies have been published on the links between land use and road traffic collisions. For example, Levine et al. (1995) investigated the relationship
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between zonal land use and road traffic collisions. They found that residential pop- ulation density, manufacturing, retail trade, and services industry were positively related to the number of road traffic collisions. A study of child road safety in Salford, England (Petch and Henson 2000) examined child injuries by Enumeration District zones, covering an area of about 100 km2 over a 40-month period. Factors related to land use, principally the number of trip attractors or trip generators, percentage of terraced housing, and amount of open space, were found to be significant explana- tory variables. Ivan et al. (2000) identified the number of driveways to the public highway on each road segment as a significant predictor of single-vehicle and multi- vehicle collisions. Researching pedestrian injuries, LaScala et al. (2000) suggested giving priority to efforts to prevent pedestrian alcohol impairment and reducing neighborhood alcohol availability. This was based on the relationship among the spa- tial location of alcohol retail outlets, demographic factors, and the road environment with pedestrian injuries. In relation to land use, the number of bars, off-licenses, and restaurants per kilometer location of activities and their spatial density have a signifi- cant role in determining the relationship between land use and transport. Land use patterns tend to be due to local decisions to respond to market demand for housing, employment, and services. In theory, land use should be planned to minimize road traffic conflict, particularly between motorized and nonmotorized transport. This can be achieved by reducing the need for motorized transport, for example, by locat- ing shops and schools within walking distance of homes. In other words, locating trip generators and trip attractors close to each other could reduce the need to travel by car, thus encouraging walking and cycling.
Kim and Yamashita (2002) compared the vehicle-to-vehicle collisions with vehicle-to-pedestrian and vehicle-to-bicycle collisions per acre land use category for Honolulu over a 10-year period. They found that vehicle-to-vehicle collisions were highest in commercial and industrial areas (6.62/10 acre year), visitor lodging (5.15/10 acre year), and manufacturing and industry (3.67/10 acre year). The order was somewhat different for vehicle-to-pedestrian collisions with visitor lodging (0.43/10 acre year), commercial and industrial (0.30/10 acre year), and public ser- vices (0.20/10 acre year) being the three highest categories. The vehicle-to-bicycle collisions followed the similar pattern, although the collision rates were typically less than a half (visitor lodging 0.22/10 acre year).