Town planning was previously focussed on somewhat sterile grid layouts dedicated to single usage. Areas could thus be planned to have a residential usage, or be oriented towards
CONtENtS
2.1 Introduction ... 17 2.2 Land use policies ... 17 2.3 Policies relating to network planning ... 19 2.4 The policy of the ‘complete street’ ... 21 2.5 Geometric design as a ‘precise science’ ... 22 2.6 Policies related to design ... 23 2.6.1 Cost-efficient design ... 23 2.6.2 Access control ... 24 2.7 Conclusion ... 25
18 Geometric design of roads handbook
commercial or industrial applications. The fact of the matter was that everybody had to move from home to job and back again in the evening. The proliferation of the passenger car resulted in many people being able to enjoy the convenience of using their own car to get to work. Home was generally in some outlying residential suburb and the workplace was either in an industrial area or in an office in the central business district (CBD).
Congestion, air pollution, rat-running and noise were inevitable accompaniments to the single-usage township layout. A further consequence of this layout was that people relied on their cars to get anywhere and did not exercise much, if at all, resulting in a population that included 25 per cent obese people, many of whom were morbidly obese.
More recently, a cellular policy of township layout has emerged and the single-usage layout largely abandoned. Basically, the ‘cell’ would be surrounded by arterials and have relatively few accesses to the arterial network, with no portion of the internal road system serving as a short cut to anywhere. In the case of existing grid layouts it would thus be easy to eliminate rat-running through the community altogether. The land usage inside the cell could include high- and low-density residential accommodation, local retail outlets, possibly light industries and other employment opportunities, schools, churches and recreational areas. In a cellular multi-usage township the ‘home above the shop’ is a distinct possibility whereas the single-usage policy precluded this.
A cellular township layout is illustrated in Figure 2.1.
Legend Arterial street Commercial area Local street Collector street Public area
Figure 2.1 Typical cellular township. (From American Association of State Highway and Transportation
Policy 19
Many people would be able to walk or cycle to work within the cell area, thus getting healthy exercise while simultaneously reducing the pollution caused by hydrocarbons. The employment opportunities in the township would have an obvious although possibly restricted impact on the traffic on the arterials. One of the more obvious benefits of the cel- lular policy is that it would engender a strong community spirit.
In the case of existing grid layouts, the application of the cell concept is achieved through the application of traffic calming. Traffic calming is a retrofit application to eliminate rat- running, amongst other things. It is aimed at reducing both the speed and the volume of traffic of traffic in a residential area. This is briefly discussed in Chapter 13.
An important aspect of land use is that it should seek to minimise the footprint of the road, which is the extent of land required for the provision of the road. This is required to ensure that land that could have been used for other profitable purposes isn’t sterilised by incorporation into the road reserve. An example is the insistence on an overly generously sized median island. Examples exist whereby the Transportation Authority demanded and got a median island with a width of 20 metres on the basis of the distance that an out-of- control vehicle would travel beyond the boundary of the travelled way. The assumption made was that this vehicle would not travel further than about 10 metres away from the travelled way. If two vehicles travelling in opposite direction were to cross the median simul- taneously in an out-of control fashion such that they could collide, the likelihood of a fatal crash would be high. Hence the need for the 20-metre width!
Obviously, the likelihood of the precise location of the two vehicles on departing from their carriageway and their subsequent paths being such that a crash will occur is vanish- ingly small. A 20-metre wide median that is, say, 50 kilometres long occupies an area of 100 hectares forever removed from economic activity.
The need to accommodate the desired cross-section and ancillary features such as drainage of the road and widening of the road reserve to accommodate intersections or interchanges as well as space for utilities must be the basis of the determination of the footprint of the road.
Having established the extent of this footprint, the land required has to be acquired by the Transportation Department. This is often by an agreed on price on the basis of a willing seller/willing buyer process. Unfortunately it also happens that agreement on the purchase price sometimes cannot be achieved, usually because the value that the seller attaches to the land to be acquired is unrealistic. It would then be necessary to go to a process of expropria- tion whereby the seller is forced to accept the purchase price offered. Normal practice is that the price offered is market related. In some countries, the acquired land is legally transferred into the name of the Transportation Authority through a deed of sale or equivalent mecha- nism, whereas in others the acquired land is not transferred but remains the property of the owner even though he or she does not derive any benefit from ownership of the expropriated land. Some countries levy taxes to finance the upkeep of the local road system, with these taxes being based on the area of the owned property. In these cases, not taking transfer of the land would be manifestly unfair.
The creation of the road reserve may result in portions of the property being alienated from the remainder of the property, for example, without access from the remainder and being too small to be operated as an economic unit. The alienated portion should then be incorporated in the footprint of the road reserve.