PLANNING INDICATIONS
7.1.2 Planning of roads and railways (routing)

Even if city planning is usually less concerned with the large-scale planning of roads and railways, we would like to treat a selection of planning principles in this context.

In sound technological terms, it is advantageous to plan the route of e.g. bypasses and railways as far away from uses requiring protection as possible. This also means that uses requiring protection, e.g. residential areas, must not come close to existing bypasses (fig. 7/1). A doubling of the distance between the two uses leads to a level reduction of 3 to 4 dB (see fig. 3/4 in section 3.1.2.4). This shows that the displacement of the routing has only minor effects if the distance between transport route and place of immission gets bigger.

Wherever possible, roads shall be planned and constructed in a way that traffic can move slowly and uniformly. Roundabouts are therefore preferred to normal crossings in this context. Rapid sound level increases through braking or starting vehicles (see section 7.1.5) cause particular disturbances. This is why RLS-90 consider the nuisance factor of signal-controlled crossings with a sound level addition of up to 3 dB when determining the rating level.

Slopes also have negative effects on the noise level. The lower the gradient, the lower the noise pollution. The provision of RLS-90 defining that only slopes as from a gradient of 5 % shall be taken into account does not go far enough as also slopes with a lower gradient make themselves heard due to the vehicles' higher engine speed and thus lead to more disturbances for the residents.

As mentioned before, the concentration of transport routes ("noise to noise" principle) is advantageous in sound technological terms. Existing noise sources shall therefore be taken into account in the planning of roads and railways. The path of future transport routes is best aligned along existing sound sources, e.g. a road along existing railways. Noise pollution in the area of the existing transport route is often only slightly increased and areas not exposed to noise remain quiet.

Planners should consider topographic elements which are favourable in sound technological terms, e.g. indented positions, when selecting the route.

In the context of the construction of bypasses, the affected population must be further relieved through traffic calming measures (fig. 7/2) and the renaturation of existing through roads.

An adequate and sufficient curve radius must be considered along the course of railway lines. Narrow curves lead to squeaking noises and to sound level increases of up to 8 dB.

Curve radius and gradient of the route should be favourable for the tram dynamics. The speeds on the individual track sections should be adapted to the type of use of the area along the tracks and the individual urban development situation. Standalone tracks should have a curve radius and continuous tracks that allow for the use of the maximum speed in track curves.