1.1.3.1 Global Urbanisation
The proportion of the world’s population living in urban areas is increasing rapidly. The exact figure depends on the definition of an urban area, which varies significantly between countries, and thus is very difficult to produce. For example by Swedish census methodology, 200 people is considered an urban settlement, whereas in Mali, the minimum is 40,000 [64]). It is widely accepted that more than half of the global population is living in towns or cities, up from 30% in the 1950s [65]. That percentage is expected to rise to 85% by 2050 [66]. In total this corresponds to 3.9 billion people living in urban areas worldwide today, up from just 746 million in 1950. By 2050, an additional 2.5 billion people are expected to be living in towns and cities. This figure is made up of a combination of both population growth and rural to urban migration.
The gap between the developing and developed countries must also be considered. In the UK, the urban proportion of the population (which had been steadily just under 80% since the 1950s) is now at 82% and expected to reach nearly 90% by 2050, a pattern which is repeated across other developed countries [65, 67]. However, despite the lower proportions of urban residents in developing countries, the absolute numbers are higher. Asia alone contributes more than 50% of the world’s urban population, whereas Europe contributes just 14%. In terms of growth, the urbanisation process is happening fastest in Africa and Asia (these two continents are expected to generate more than 90% of the increase). India, China and Nigeria alone are predicted to account for 37% of urban population growth by 2050 [65].
An additional distinction is the size of the cities. Of the world’s population, only one eighth live in so-called ‘mega-cities’, with more than 10 million inhabitants [65] (of which there are 28 worldwide). By contrast, more than half live in towns or cities with a population of less than 500,000. Whereas in 1950 the majority of the world’s largest cities were found in developed countries, most mega-cities now are found in developing countries. The fastest- growing type of city is mid-sized cities in Africa and Asia, with between 500,000 and 1 million inhabitants [65].
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1.1.3.2 Impacts of Urban Freight
High population density creates a number of challenges for providers of goods and services to those populations, which will only increase as the world’s population becomes increasingly urban [68]. Transporting goods into and waste out of city centres must be done by road in almost every case, which generates a high volume of vehicles on the roads, both personal and commercial. This usually contributes significantly to congestion, and causes additional problems such as high noise levels, risks for vulnerable road users and greenhouse and noxious gas emissions [68].
Managing urban freight activities can be a complex task, as there are many competing goals to be balanced [69, 70]. These include national authorities seeking to limit Greenhouse Gas emissions; local authorities looking to manage congestion, noise and air quality emis- sions; operators attempting to minimise costs; residents avoiding noise (particularly outside of working hours), and all parties wishing to improve safety.
McKinnon et al. refer to the concept of negative externalities associated with road freight [38]. These can be considered the ‘non-financial costs’ of moving freight on the roads. For example the effect on public health of reduced air quality due to freight vehicles in urban areas is a negative externality. (In this case, there is a financial cost, but it is borne by the health service, rather than the freight industry.)
The externalities of road freight in urban centres are different to those on long-haul routes. First, noise pollution becomes a much more significant factor when there are people around to hear it [71]. Secondly, while greenhouse emissions are a negative externality for all freight vehicles, noxious emissions are only really a problem in densely populated areas [72]. Thirdly, congestion is a serious negative impact of increased freight vehicle traffic on urban routes [28]. Finally, there is the risk of damage to infrastructure, or collisions with vulnerable road users [73, 74].
One additional difference between long-haul and urban driving is that drive-cycles in city centres are much lower average speeds, and include a lot more starting and stopping [75, 28]. This makes them ideal candidates for electrification, but in the short term means that the fuel economy and therefore emissions statistics are poorer for urban vehicles than long-haul vehicles.
A simple approach to reducing the negative externalities associated with urban road use is to reduce the number of vehicles on the roads. As well as reducing emissions and noise and improving safety, this would also reduce congestion, which has a further effect on emissions, since vehicles spend less time stationary [28]. Treiber at al. [76] showed that reducing congestion can inherently reduce vehicle emissions by up to 80% in extreme cases, simply by reducing the length of time vehicles spend on the road idling.
12 Introduction
1.1.3.3 Barriers to Higher Capacity Urban Vehicles
There are a number of pressures or perceived pressures limiting the size of current urban vehicles.
Negative public perception Negative public perception of heavy goods vehicles has lead to strict legislative controls, and reluctance of operators to switch towards larger vehicles. Larger vehicles are generally seen as being more polluting, and more likely to cause damage to structures or to cause accidents involving vulnerable road users [77]. In fact, research into Long Combination Vehicles by Woodroffe showed that larger vehicles are often safer, due to the fact that fewer of them are required, and that operators tend to use their best drivers for their biggest vehicles [78].
Woodroffe’s study showed that the crash rate of Long Combination Vehicles operating under a special permit in Alberta was five times less than standard tractor semi-trailers on the same roads [78]. This was partly attributed to the special permit required to operate the vehicles. A report for the Department of Transport in the UK evaluating the trial of longer semi-trailers showed a 70% drop in accidents on a per-km basis for longer semi-trailers compared to standard semi-trailers [79]. Similar results have been observed in the RTMS programme in South Africa [80], and for higher capacity vehicles in Australia [81].
Increasing capacity of freight vehicles will lead to some decrease in traffic congestion [82]. This can be attributed to the reduced number of vehicles required for a given freight task, despite a marginal increase in length per vehicle.
Legislative limits An important barrier to higher capacity vehicles for urban delivery applications is the UK definition of a Light Goods Vehicle (LGV), which must have a Gross Vehicle Weight (GVW) of less than 3.5 t. Consequently vehicles weighing less than 3.5 t do not require drivers to hold an HGV license, or follow HGV driver shift length rules, or the vehicle to be fitted with a tachograph [83]. These would increase operating costs significantly, making it uneconomical to use a vehicle larger than 3.5 t unless a significantly larger vehicle was feasible.
As a response to recent consultation with operator associations, the Department for Transport has relaxed this limit for ‘alternatively-fuelled’ vehicles to 4.25 t [84]. This is intended to mitigate the payload penalty caused by the increased weight of alternative power-trains, such as battery weight.
For larger vehicles such as tractor semi-trailers, the maximum dimensions are set by the standard roundabout test [63]. To pass, the vehicle must be able to turn through 360° without exceeding an outer radius of 12.5 m, or an inner radius of 5.3 m.
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Manoeuvrability If larger vehicles are required to access the same roads as smaller ve- hicles, then any given vehicle is more likely to cause damage to infrastructure or accident involving other road users, due to the manoeuvrability penalty of being larger [5]. Vehicles with a larger wheelbase have a wider turning circle and so require more space to turn. Ve- hicles with a longer overall length and therefore longer overhangs from the front and rear wheels have larger ‘frontswing’ and ‘tailswing’, thus can collide with obstacles. These effects will be described in more detail in the following chapters.
Vehicle fill and driver workload Since using a single, larger vehicle instead of a single, smaller one for a given route causes higher fuel consumption, it is clear that unless the larger vehicle can be filled, the smaller vehicle is the more suitable. In other words, if a larger vehicle is not carrying more freight than a smaller vehicle, then the smaller vehicle should be used instead. For some logistics operations a fleet of larger vehicles is less efficient.
Similarly, for operations where increasing capacity means increasing the number of vehicle stops (such as home delivery) rather than the size of each drop, the length of time required to make all the deliveries from a larger vehicle could exceed a sensible driver shift length. This would then incur additional costs of returning to base to swap drivers (in which case the vehicle could be reloaded anyway) or arranging for drivers to meet out on the route. Therefore it is necessary to match the size of vehicles to the number of deliveries that can be completed in a single shift.