ROADS PLANNING Roads are skeleton of any town plan, or, to vary the simile, the arteries of the organisms through which the life blood of communication flows. The planner must necessary let the road engineer have the last word regarding road material, gradient camber, super elevation, radii of horizontal and vertical curves, etc through he should be well aware of the technical factors governing them, and he should regard the traffic engineer or traffic planer as an indispensable colleague. This is not to imply that sheer traffic efficiency should be determinant in preparing the town plan, for numerous other factors may well be of equal or greater importance, but certainly a Town Plan which dose not ensure the efficient flow of traffic is little more useful than an aircraft which will not fly. Roads are of greater antiquity.
They were original pedestrian track along which, before the invention of the wheel, loads might be dragged on rough sledges; they became, as human civilization progressed, routes along which animals were driven, led or ridden and horse drawn, later, mechanically propelled vehicle traveled. Always, roads have had a dual function: as traffic routes and as means of access to dwellings and other buildings; it is only since the vast growth of transport which has arisen from the invention of the internal combustion that these have been seriously in conflict with each other. Today this conflict is very grave, and leads to terrible injury and loss of life and to grossly wasteful delay in the transport of worker and goods. A casual inspection of road traffic is apt to give the impression of a vast number of vehicle moving about the country in random fusion, but this impression is false. It is remarkable that the average length of a vehicle journey in this country is only six miles. Traffic forms definite patterns which vary form day to day and at different times during each day.
Nearly all journeys have a purpose, so that careful observation of existing traffic part tens and analysis of the number of people likely to visit traffic-attacking uses to be established in the future road requirements. In early of the morning there are usually very few vehicles on the roads -in the U. S. A, this traffic is termed as the "O. W.
L." Around 6 a. m. , however, early manual workers appear on the scene, together with vehicles delivering milk, newspapers, etc. This traffic builds up to peak, usually before 8 am, to be joined by the and school traffic. The office traffic may continue sporadically until about 10 a. m but by 9 p.
m it has diminished greatly even on few specially heavily used routes, while else where it has virtually disappeared. Traffic then falls to a level well below the daily average, being made up of local delivery traffic, but the morning progresses flows tend to build up again as the business traffic increases, and a small quantity of shopping traffic joins the stream. By 11. 30 a. m flows are usually about equal to average hourly flow for a sixteen -hour day (6 am - 10 pm) and the hour of 11 am to 12 noon is a useful period to assess this figure.
Owing to the universal habit of lunching at some time between 12 and 2 pm traffic declines again during this period although there may be short burst of 10 to 15 min when flows are considerable. By 2 pm flow have returned to average. In the afternoon of typical weekday flows increase again because of commercial traffic. By 4 pm children are returning home from school, commercial vehicle are returning to their to their depots, and mothers who have been shopping are returning home to their children; flows tend to increase appreciably at this time. Some manual workers finish work as early as 4. 30 pm, but most do not finish until 5 pm or later; office worker tend to finish work between 5 pm and 5.
45 pm and so the evening peak period tend to be more compressed, with flows higher than in the morning. After 6 pm much depend on the nature of the road and the time of year as to the amount of the amount traffic which it carries but as general rule flow s tend to decline appreciably as the evening wears on, except for a short peak about 10. 30 pm when the pubs close. By midnight, nearly all the evening social travelers are home and flows are once more down to the OWL level. Although the above is generally true much depends upon the location and nature of the road. A radial road linking extensive dormitory development with a central area will tend mostly to carry office workers on their morning evening surges, with much smaller volumes of traffic during the rest of the day.
Conversely, a minor lateral road will a more or less uniform flow through out the day. As, a general rule, a road system which has been designed to carry the work -tip traffic will have sufficient capacity to accommodate all flows during the remainder of the day, though there are exception in the immediate vicinity of shopping centers, football grounds and roads carrying large volumes of racing or Hoilday traffic. A great difficulty in di suing road design is that one is inevitably drawn to the use of expressions which have not been closely defined and which indeed, may be incapable of precise definition. Congestion, 'free flow ', 's safety ' are three of special important and difficulty. Statement of extreme are sometime useful in such circumstances. Completely free flow and a complete absence of congestion and danger imply condition in which the driver of motor car can get into it, starts his journey and immediately accelerate to what ever speed he wishes and his vehicle is capable of sustaining, maintain this speed until he slows down on approaching his destination and having, during this journey, endangered nobody.
It is not possible to think of a road system being constructed which would make this a reality. The extreme of danger on the other hand, represent condition in which no vehicle can be driven anywhere at any speed with out endangering life; while the extreme both of congestion and absence of free flow can be defined as condition in which vehicle on the road cannot move and vehicle off the road cannot be driven on to the roads. These, at times, seem less impossible of fulfillment. What sort of standards, then should be sought? As to safety life itself is a chancy, uncertain affair.
Accidents of many kinds tragically kill and maim many people. we cannot hope to eliminate all accidents associated with motor vehicles. We can, however hope to reduce them very by creating condition in which only gross stupidity or or real accidents (a wasp in the eye, sudden heart failure) produce accidents An important, and as it seems to me, obvious first step in this direction is to regulate the design of motor vehicles by law so that they are incapable of standards of performance, in terms of top speed and acceleration, which are not matched by the engineering and other standards of the roads system which we decide we can afford. an overall speed limit of 70 m. p. h.
seems to me sensible provision but it would be much more effective if no cars were made for use on public roads which were capable of traveling at more than 70 m. p. h. Damping down acceleration performance so that dangerously lively driving in minor road system is made difficult is perhaps more complicated but is hardly insoluble. This is no matter with in the scope of planning control. A realistic road design programme would be, I think, one to ensure safe travel at 70 m.
p. h on arterial roads outside towns, at 40 m. p. h on arterial roads inside towns and major roads and at 2 0 m.
ph an all minor roads. Free flow and congestion can be regarded as opposite sides of the same coin, and it is were possible every hard to suggested in the preceding paragraph one could clearly regard standards as being very high. But the great problem is that if the roads are designed so that they can cope with peak hour traffic (particularly if the peak is a 'sharp' one of short duration) they will be very much more costly and capacious than is necessary most of time. If one suggested that, at worst, an average speed of 20 m. p. h should be possible for journey with in towns this would be an apparently modest standard yet sufficiently speedier than travel on foot to be worth while and much faster than is achieve with in many towns at many times.
Useful discussion about the problem of planning road system depends partly upon designing a clear and valid system of terminology for distinguishing between different types of roads. Roads fell into three main classes-'arterial', 'sub - arterial' and 'local' - the first carrying great masses of traffic between towns or between different parts of same town, the second linking network of local roads with in reach other and with the arterial roads, the third having the main function of giving access to premises. This is a convient nomenclature, although it is not always easy to decide which roads should be placed in the intermediate class of 'sub - arterial'. Roads in urban areas follow the classification as: PRIMARY DISTRIBUTORS: These roads from the primary network for the town as a whole.
All longer-distance traffic movement to, from and with in the town should be canalised on to the primary distributors. DISTRICT DISTRIBUTORS: These roads distribute traffic with in the residential, industrial and principal business district of the town. They form the link between the primary network and the roads within environmental areas (i. e. area free from extraneous traffic in which consideration of environment predominate over the use of vehicle. ) LOCAL DISTRIBUTORS: These roads distribute traffic with in environmental areas.
They form the link between district distributor and access roads. ACCESS ROADS: These roads give direct access to buildings and land with in environmental areas. THE URBAN ROAD SYSTEM The problem of designing new roads and road systems and improving existing ones are obviously different, and it will be convenient to deal with them separately and in that order. The arterial roads is commonly linked to a rail way, in as much as the criterion of its success is the extent to which it provides a route along which motor vehicles can proceed safely and uninterruptedly, except at infrequent controlled points, at speed comparable to those of trains.
It follows that, except at these infrequent controlled points, there should be no intersections with other roads and that no buildings should have direct access to the road. These requirements are accepted as absolutely essential for railway but are still sometime regarded as startling or impracticable in relation to roads; yet, in fact, the dangers of uncontrolled intersection and access points are vastly greater in case of arterial roads than of railway. Large units (trains) pass along the railway lines at fixed and relatively infrequent intervals at a fairly constant speed, but hordes of vehicle traverse arterial roads in no special order and at considerably varying speeds. The danger of accident bear no comparison; yet, although to build a row of houses fronting directly on to an unfenced railway would be regarded as the act of a lunatic, such a procedure beside an arterial road was common from between the wars.
The reason forthe difference in view point is fundamentally, that the railway came to life in a virtually mature form, with every one alive to its dangers, whereas the long history of the roads and its dual function delayed public opinion from insisting upon similar restrictions to the frontage of arterial roads. Arterial roads can appropriately be sub divided into the following principal types: O National and regional through routes which link different parts of the country, avoid towns, and are fed byO Main radial routes running through towns and joining them to other towns. O Town ring or lateral roads which link the radials. An outer ring road may also join, or, for a short distance, merge with a national or regional through route. National and regional through routes. Pedestrian and cyclists have no place on national and regional through routes, and there is, therefore, no necessity to provide either cycle tracks or footpaths along them.
The sole points at which access should be provided are at junctions with other roads of the same kind and with feeder roads from nearby towns and for occasional filling and service stations and places of refreshment. Through routes should bridge or underpass all roads other than their feeders. They should be planned to allow vehicles to travel fast, and gradients and curves, both horizontal and vertical, should therefore be of the easiest. The necessary components are simply two unidirectional carriageways of sufficient width to carry the volume of traffic which will use them. The physical separation of fast-moving streams of traffic moving in opposite directions is, of course, essential for the avoidance of head -on collision, and the removal of this possibility materially relives the strain and fatigue of driving. Fatigue may also be reduced by other means which, fortunately, also assist in enhancing the visual attractiveness of the road itself and in reducing its inevitably marked effect upon the landscape.
It is undesirable that a road should run dead straight or dead level for any great distance, for the monotony which this causes exerts a marked hypnotic effect on long journeys and may contribute substantially to a driver falling asleep at the wheel, with hideous results. The route may therefore, within reasonable limits, follow contours, hedgerows, and the sides of woods, which helps the roads to fit in with the landscape rather than violate it, and enables interference with farm units to be minimized. Similarly, it is unnecessary for the carriageways to run parallel to each other. They may, appropriately, diverge to considerable distance at some points, and may run at quite different levels in hilly country. Ring and radial roads: Cyclist and, in some cases, pedestrians, may have to be provided for along these, which afford the main communication between different and parts of the towns although it is desirable that motor traffic, Cyclist and pedestrians should be effectively segregated on all arterial roads, which means not only that separate tracks must be provided for each, but that each class of user must be physically prevented from straying off his own track on to that of another class. It is, for example, not good practice to place a foot path immediately adjoining a carriage way, since pedestrians can, and often do, step off and get knocked down by motor vehicles.
A good solution is to combine physical separation with park way treatment of the road if land availability allows. If this is done the total width of the road is considerable; each element of it is separated by a substantial strip of land and the part of the road not occupied by carriageway, footpaths and cycle tracks are given landscape treatment, not in an attempt to simulate the open countryside, but in a more sophisticated fashion appropriate to urban area. As radial road approach the town center and converge upon each other parkway treatment is unlikely to be possible, and it will then be necessary for separation of the different elements to be achieved by fences, hedges, walls or embankments. The need for pedestrians to cross the road is likely to become greater as the center is approached, and in order to preserve the safe traffic, bridges or sub ways should be provided for them at suitable points.
Some general aspects of radial and ring roads must be consider. Rush -hour traffic creates a special problem on radial roads, since most of the traffic travels in one direction in the morning and other direction in the evening. This can be solved in two ways. One is to have triple instead of dual carriageways on the radial roads.
The direction of traffic along the center one being changed twice daily to accommodate the excess traffic; the other is to place moveable division along a single carriageway width devoted to each direction of traffic flow, in accordance with temporary condition. A third possibility is to use illuminated overhead signs to indicate which lanes are to be used but this method is obviously less safe though cheaper than the others. The inner ring road: This road is of very special character, it will wholly or partially encircle the central area of the town; on its outer side it will be joined by radial roads and on its inner side by roads leading into the central area; the town's bus station must be necessarily be located close to it. Traffic will be very heavy and intersections numerous, so that high average speed of traffic will not be possible.
The main objective must be a continuous and safe flow of traffic. Segregation of motor traffic and pedestrian is more essential than elsewhere, and since width is likely to have to be restricted, can best be achieved by vertical rather than horizontal barriers. Cyclists become a serious problem; it is desirable than they be segregated because of the great density of traffic to be expected, yet the cost of their segregation becomes prohibitive, since, to be effective, cycle tracks must cross intersections either above or below vehicular level, and, as already noted, intersections are numerous. Although result obtained by methods other than spatial arrangement are really outside our terms of reference it seems reasonable to suggest that cyclist should not be permitted to ride in the inner ring road, but be required to wheel their cycles. MAJOR ROADS: They include all those which are joined by numerous minor roads. They comprise roads within the central area, the principal roads within industrial areas, and the principal roads within residential neighborhoods, to which the minor roads connect.
On these roads high speeds cannot be permitted because of the multiplicity of road junctions, each of which is a danger point, and it is therefore less necessary to segregate different classes of road use, as well as being impracticable. Adequate widths of carriageways and footway's, and the maintenance of sufficient straight lines at junctions are of first importance. The whole road system is like a river, with its tributaries, stream and brooks, all bearing water to each other in varying quantities. At some point there necessarily has to be a road which, having gathered the traffic from the minor roads and cut-de-sac which flows into it, because of some traffic but which, because of economy and indeed of convenience of lay out, nevertheless has to be treated as minor road to the extent of having a large number of minor roads leading into it at ordinary uncontrolled junctions. These road may also carry local bus services. The first requirement is not to make roads of this kind too long and straight, for this, even though a speed limit is enforced, will encourage dangerously fast speeds.
But this is not too easy to contrive with out serious disadvantages. It is important for numerous reasons that the major roads of residential area, and should carry traffic reasonably directly. In the absence of directness the structure of the neighbourhood tends to break down into a formless 'medi veal' pattern in which accessibility is severely reduced and the multiplicity of turning movements at road junctions may, quantitatively, create more dangers of speed on straight, direct spine road. MINOR ROADS: First the requirement for these are, that the system of minor roads should not afford opportunities for the astute motorist to take short cuts through it instead of using the arterial and major roads; deliberately design of the lay out is necessary to secure this.
Second, the imposition of a speed limit is, of course, essential, but in addition, along, straight lengths of road should be avoided so that the lawbreaker is discouraged. Third, the capacity of the road must be sufficient to allow the free passage of vehicles are parked outside buildings. Fourth, sight lines at junction must be adequate, and direct intersections avoided. However few the vehicles which use minor roads a collision is always possible at an intersection, and can be just as serious as one on an arterial road.
Fifth, roads are very costly to construct, and the total lengths and widths of minor roads constructed should be kept to the minimum consistent with fulfillment of the foregoing requirements. The footway and carriageway widths of minor roads must be graduated according to the amount of traffic likely to use them. The residential cut-de-sac will not be used by the people living in it and those who call on them. Several cut-de-sac may open on to the same minor through road, which will be used by the people going to and from the cut-de-sac in addition to those using the through road itself. This increase of traffic volume continues progressively until eventually a major road must be provided. Roads have to be fairly wide to enable vehicles to pass each other and to allow space for parked vehicles.
The remaining element which can be varied, through few attempts have so far been made to do so, is that of smoothness. It is certainly possible, and in my view is desirable, to insist on minor residential roads being constructed with a very irregular, wavy surface so that any speed greater than, say 15 miles an hour would result in great discomfort to motorists and peril to the springs and back axles of vehicles. At first sight this idea may seem eccentric but it is rooted in common sense. It may be impracticable to limit the speed, and hence the danger to pedestrians, of motor vehicles by appeals to law or common sense; physical limitations, however, are less easily ignored. Speed within a residential area, has to be sacrificed to safety; the motorist has moved out of the road system proper and is simply threading his way to a destination. Experiments on these lines have already been made by making humps or gutters across private residential roads to limit speed.
It would be easy to design roads deliberately with similar configuration but in a way which would keep the road in a stable condition instead of subject progressive deterioration. Very pleasant visual effects could be worked into the designs. A different method is the use of 'Ripple bars. These are humps running across a carriageway which can be to added existing roads. They are placed 60 to 70 yards apart and rely for their effect upon the discomfort they produce to the occupants of vehicles which cross them at more than 15 m.
p. h. they are used in various places.