Nearly 1,000 miles of great new express motorways, or Autobahnen, as they are called, have in recent years been built in Germany. Ingenious flying and burrowing junctions have been built to assist the flow of traffic
BRIDGE-BUILDING for the new motorways of Germany has given employment to thousands of men in steelworks and associated industries. The new roads have involved the building of numerous bridges and viaducts across rivers and valleys. Where possible the natural stone of the district has been used for bridges and masonry piers so that they will harmonize with the scenery.
IN all countries there is a movement for the amelioration of roads, to keep pace with the ever-increasing speed and density of motor traffic. Not only are existing roads being straightened and widened, but express highways, reserved for motor vehicles, are being built also.
In no country have there been more striking developments than in Germany. Nearly 1,000 miles of motorways have been built in recent years. As will be seen from the map below, these motorways extend north, south, east and west. In each of these roads a central strip separates opposing streams of traffic and level crossings are eliminated by ingenious systems of road junctions. Speeds as high as 150 miles an hour can be attained with safety.
Even in backward regions the authorities are bound to improve the roads, for not only the convenience of the public but also economic considerations demand the modernization of streets and highways, as well as adequate realinement in the interests of safe driving. Relatively high consumption of motor spirit and lubricating oil, rapid depreciation or even fatal accidents may be due to the -bad layout and imperfect maintenance of a country’s roads. Thus the question has become one of national importance.
It does not normally pay to build express highways in regions sparsely populated and poor in natural resources, though the existence of good roads tends to induce the inhabitants to improve their standard of living. Peasants get into touch with hitherto unattainable markets; financiers become inclined to develop the country wherever possible. The distance between town and country decreases; the poorest farmer longs to participate in the amenities of town life, and he will work and produce more and more until he can buy a cycle, a motor cycle and finally a motor car. It is the ideal of the youth everywhere in the world to-day to sit at the steering wheel of a car, preferably a car of his own.
Farm-to-market traffic covers only one part of the problem. The exchange of goods between the industrial centres is also of importance. The lorry offers special facilities in the way of door-to-door conveyance of goods between the factories and the buyers. Mass transport, however, will probably never leave the railways, especially when the railway administrations modernize their rolling stock and goods depots.
The motor tourist has become a factor of prime importance. The money spent by motorists visiting a foreign country has its effect, as an invisible export, on that country’s finances. No Government, therefore, can afford to neglect such a prolific source of revenue.
A NETWORK OF MOTORWAYS is being built for fast motor traffic in Germany. This map show, the roads that have been planned and those that were completed or under construction in 1937. Nearly 1,000 miles of double carriageways had been completed in that year. They included roads between Berlin and Stettin, Lubeck and Bremen, Konigsberg and Elbing, Hanover and Berlin, Cologne and Duisburg. Giessen, Frankfurt, Mannheim and Karlsruhe have been linked, and in 1937 the whole of the extension through Stuttgart, Augsburg and Munich to the Austrian frontier at Berchtesgaden was either under construction or completed. Breslau, Dresden, Leipzig and Bayreuth stand on completed portions of the great network and links in every direction are under construction.
When planning new roads the authorities have to consider the probable quantity of products which agricultural and mining centres will transport in present and future years, the movement of settlers and tourists, and the distribution of industrial products in the country.
The layout of roads depends on geographical factors, though dense traffic would justify the building of costly bridges, the penetration of swamps, or the boring of tunnels through mountain ranges. If one car or lorry has to consume a shilling’s worth more petrol by taking a circuitous route instead of a direct thoroughfare, 500 motors daily would waste over £9,000 in a year. Even if a new road, with its bridges and viaducts, replacing the old and longer road, were to last only ten years, the sum of £90,000 could be economically spent on its construction. This calculation takes no account of probable increase of traffic.
An important factor in road planning is the competition between road and rail. In some instances the existing railways cannot suffer the competition of cars and lorries and will close down. On the other hand, new roads, especially those serving as feeder roads to the railway stations, will help to increase the railway traffic. The German Government is claimed to be the first to have elaborated plans for the future of motors and motor traffic. It was the personal idea of Herr Adolf Hitler to create a network of motorways combining the results of technical research and of economic and geographical investigations.
The Chancellor wished to promote motor traffic as far as possible, and allowed for a considerable increase in the speed and number of cars and lorries. Having motored thousands of miles in all parts of Germany, he was well aware of the former bad condition of German roads. He realized that shortsighted repair work would be of little use, and that new construction offered the best solution. Germany and Italy had already planned motorways since 1925, and American express highways were in existence, but the new German road system was to be unique in its technical details as well as in its general layout.
The planning of a network comprising great thoroughfares from east to west and from north to south was also to be of fundamental importance to transcontinental traffic, which the central situation of Germany in the heart of Europe attracted in large numbers.
Because of the former bad condition of the general road system the number of motor vehicles in Germany was relatively low —only one car for every hundred inhabitants. Therefore the building of better roads was especially calculated to promote an increase of internal motor traffic in Germany.
Since the opening of nearly 1,000 miles of motorways in Germany the number of private cars and lorries has greatly increased. The general road system has been improved also. The motorways are not isolated, but are connected by numerous feeders with the country roads.
DOUBLE CARRIAGEWAYS are universal on the German motorways. The strip between the two tracks is generally 16 ft. 6 in. wide. Each track is 24 ft. 6 in. wide. The roads are designed for speed, so there are no level crossings or ordinary intersections, and corners are banked. The photograph shows a portion of the motorway between Munich and Berchtesgaden, in South Germany, on the Austrian frontier.
The planning of the network not only had in view the traffic between industrial centres, harbours, mining and agricultural regions, but also envisaged areas not yet fully opened to traffic. Germany has about 50,000 communities, of which only 12,000 have railway connexions. The motorways have therefore been planned with an eye on these neglected areas.
The motorway programme in Germany forms an important part of the labour scheme in combating unemployment. About 100,000 men have found new jobs on the motorways, and another 150,000 have been able to work on the building of bridges, in quarries, steelworks, factories and associated industries.
The German Government’s aims embody the suggestions of practical motorists as well as the advice of technical experts, the object being motorways which offer the greatest margin of safety in all conditions of traffic.
Special attention has been given to the preparation of the foundations. It has sometimes happened that a newly-made road will, after some months, suffer from the effects of subsidence. The German authorities are determined that no such defect shall develop on their motorways.
Geologists and soil specialists have been asked to ascertain the bearing capacity of the subsoil and to give practical hints. Soil testing in connexion with laboratory work has been adopted in many instances, been made of such devices and tamping machines obtain compact subsoil.
The vibrating machines used to transmit oscillations through the subsoil, and seismographic readings are taken at various distances from scene of operations.
The tamping machines vibrate the concrete laid out on the road bed. Oscillations up to 4,000 blows a minute compact the concrete and expel superfluous water; the same apparatus accurately levels the surface.
Excavated material is deposited in layers varying in thickness from 1 ft. 6 in. to 3 ft. 6 in. Consolidation of the ground, when filled, is effected by the use of drop hammers or consolidating machines in which four hammers operate side by side, over 90 per cent of the new roads concrete is used throughout. Bituminous surfacing and small stone setts are used for the remainder. Several reasons have been given for this marked preference for concrete. It is claimed that concrete roads are safer, cheaper to maintain, and provide smoother running surfaces than roads made up of any other material.
When concrete construction has been adopted, the builders have used reinforced concrete slabs. The slabs have a thickness of 8 in. to 10 in., and the steel mesh reinforcement is 4 lb. to the square yard. The standard chemical content of the concrete is 528 lb. to the cubic yard.
In the early days of construction the concrete was laid in two courses of different grades. The upper course was of better quality than the lower course.
It was, however, soon found desirable to change this method, and the roads are now generally built with single courses, of uniform quality. Transverse joints are spaced at intervals varying from 26 feet to 65 feet, to suit varying conditions in different parts of the country.
The concrete is laid on waterproof paper. After that the work is done by machines spanning the track and running on rails on either side. The rails are the verges, to which further reference is made below. For this reason the verges are — as a rule — the first part of the tracks to be built.
PLAN OF A ROAD INTERSECTION on the German motorway system. Vehicles wishing to turn right from A proceed down the spur road to B. Traffic wishing to turn left from one main road at A proceeds down the same spur road but turns left to D, across the second main road, continues to bear left under the motorway it was on originally, and then bears right to E. Through traffic proceeds directly from A to C and is carried across the second main road and the spur roads by bridges. Thus no streams of traffic meet or cross on the level.
The aggregate and cement are mixed to the appropriate quality at a mixing plant, and then brought to the scene of the work by skips drawn by a locomotive running on the rails which have been laid on the verges.
The mixer delivers the material into distributor buckets, which deposit the concrete where it is required.
Next the surface finisher comes into play. This machine levels the surface, tamps it and vibrates it. Virtually the whole of the work is done by mechanical means.
The newly laid concrete is protected from the effects of rain by canvas screens until it has set. It is then kept wet for a period of three to four weeks by wet sand, canvas or other means.
The Inspector-General of German Roads, who is the administrator of the entire German road network, including all kinds of motorways, has stipulated that the irregularities of surface shall never exceed 5/32 in. for every 12 feet.
In view of this stipulation, a machine has been devised for detecting irregularities; this machine records its results on an autographic diagram.
The cross-section of the motorways has been planned according to the experience of motorists. The roads are divided into two tracks, each 24 ft. 6 in. wide. The road surface has a camber of 1½ per cent. The tracks are separated by a central strip of 16 ft. 6 in. This strip makes for safety, especially in view of the dazzling effect of headlamps.
The edges of the central strip are covered with grass. The middle portion, about 10 feet wide, is planted with hedges and shrubs. To make room for cars which have to stop for repairs or other reasons the verges have been metalled for a width of about 3 ft. 3 in. The outer part of the verges, about 1 ft. 6 in. wide, may be used for hedges, lamp-posts or milestones.
This cross-section is of a unique type — so much so that the German name of Autobahn, in the same way as the Italian expression autostrada, has come familiar other countries, the Autobahnen, curves have been laid out for speeds of 150 miles an hour; the camber of the motor-the carefully engineered gradients permit the attainment of the highest speeds with safety.
One of the most striking features of the German motorways is that there are no level crossings. The driver need not fear the sudden appearance of another vehicle. Even the approaches from other roads have been designed in such a manner that the car entering the Autobahn can filter into the traffic only at an acute angle. Several types of one- and two-sided junctions eliminating level crossings have been developed. Cars can never meet cars going in the opposite direction. On these structures it is also possible to turn into the left carriageway (in Germany the rule of the road is to drive on the right).
The photogravure illustrations shows the general arrangement of one of these specially designed road intersections. In this instance the east-west route crosses the north-south route by means of a viaduct. Vehicles wishing to turn to the right from one road to another do so by means of spur roads laid at acute angles.
As traffic drives along the right-hand side of the road, a right-hand turn is a simple matter. A left-hand turn, however, is made by a form of flying junction. Traffic which is travelling in an easterly direction and wishes to join the north-south route in a northerly direction ignores the first spur road, passing along the viaduct over the north-south road and then turning to the right down one of the curved spur roads. This road turns through three-quarters of a circle and joins the northerly route at an oblique angle in the same direction as the north-bound traffic.
Natural Stone for Scenic Effect
The same kind of spur road is provided for traffic travelling in each of the four directions. Natural obstacles, such as rivers and railways, add to the complications of building these ingenious intersections, for additional bridgework is necessary on some of the spur roads.
Filling stations, repair shops, hotels and the like are being built at numerous places. Any road facility which might be required has been planned in advance.
Great care has been taken in preserving the amenities of the landscape. Gardening experts have been invited to assist in planning the road and to suggest suitable kinds of trees, shrubs and plants. Fine old trees are preserved whenever possible. This principle of making scenic roads is now applied to all German streets and highways. The aim is for the road of the future not only to be safe, but agreeable to its users.
With a view to preserving the landscape, the authorities have preferred to use natural stone in bridge building. This has a further advantage, as Germany is relatively poor in iron. The tendency to use natural stone for scenic effect is becoming more and more popular in all branches of civil engineering. Thus the Autobahn work has indirectly influenced general architecture.
It is relatively easy to build beautiful roads in mountainous districts. In the plains also every effort is being made to plant groups of trees and hedges here and there to improve the outlook. Only indigenous trees and shrubs are planted. The landscape gardeners also try to cultivate plants otherwise dying out.
It has been said that straight ribbons such as the modern motorways cannot be considered beautiful. But safety has to be put first in building such roads. The engineer puts in curves as often as he can, to guard against fatigue on the part of the drivers; well planned surroundings will also be of assistance.
FLYING JUNCTION OR BIFURCATION on a German motorway. Traffic for Frankfurt-on-Main proceeds straight ahead up the incline and across the bridge. Traffic for Mannheim bears right, along the spur road and under the Frankfurt road. In over 90 per cent of the new roads concrete is used throughout. Bituminous surfacing or stone setts are used for the remainder.