Noise protection is one important aspect among the "requirements of environmental protection" mentioned in the Federal Building Code to which the principle of weighing according to § 1 para. 6 of the Federal Building Code is to be applied in relation to other, potentially competing interests. Financial reasons are often opposed to the optimum solution to noise protection problems in city planning but also other aspects of environmental protection and structuring since noise barriers can change the landscape in a negative way and obstruct the circulation of wind near the ground.

In the drawing up of a legally binding land-use plan (figure 6/34) it does not suffice to include appropriate noise abatement measures but comprehensible reasons must be given for the selection of these measures and designations. All major aspects must therefore be taken into account for the weighing against other interests.

This is why the argumentation of a legally binding land-use plan must consider the following questions:

• Which noise sources are currently active in the plan area or the designated area?

• How can the resulting noise situation be assessed?

• Which noise sources are changed or must be added due to the planning?

• Are there acoustic characteristics like short-term level peaks or branch-specific features which must be considered?

• Do the conditions relevant for sound propagation change due to the planning?

• Which impacts do these changes have in the plan area, which noise abatement measures are possible and which measures are taken in particular?

• What is the sound level prognosis for the plan area in consideration of the applied measures and how can the intended situation be assessed?

• Are there alternative measures in order to improve the result within the meaning of § 50 of the Federal Immission Control Act, regulating that harmful environmental effects must be kept to a minimum?

The argumentation of a legally binding land-use plan should contain the information, calculation foundations, prognosis data or expert opinions on which it is based.

In some cases it may be enough to treat these questions in detail only for the critical parts of a plan area. But the cases will be rare which can completely do without considering the noise aspect. This can be true for quiet areas for which obviously no relevant acoustic changes are expected due to the planning. What must be considered in very quiet areas is the fact that even relatively slight traffic increases or new noise sources can change the situation sustainably. And new, so far unfamiliar noises particularly stand out.

Excess planning in particularly noisy urban development situations which require acoustic redevelopment can definitely improve the situation but this does still not fulfil the requirements of due noise protection. Planners are then forced to deal with the above-mentioned questions and this "on the occasion of and not due to" the planning. The indication that the noise situation in the relevant area can by no means be deteriorated does not suffice for an appropriate weighing of the situation.

The assessment of the acoustic conditions in the process of a legally binding land-use plan is based on the "acoustic orientation values" designated within Supplement 1 of DIN 18005-1 (Noise abatement in town planning). Planners must deal with the question of which measures can be taken in order to meet the sound level values or, for a minimization of the harmful environmental effects, stay below them. As the intended values are only "orientation values", they can also be exceeded. More stringent technical or urban development arguments are expected, however, depending on the extent of the predicted exceedance. A distinction should also be made between newly planned areas and already developed areas as the range of active noise abatement measures in developed areas is usually more restricted.

The Federal Building Code (§ 9 para. 5 No.1) provides for the fixing of the necessity of constructional or passive sound insulation measures in the affected areas within the legally binding land-use plan. But as such measures (like the installation of soundproof windows) can only create indoor environment quality to a limited degree, the earmarking for noise abatement must by no means degenerate into a universal remedy for all situations in which mostly very high noise barriers should rather be avoided or cannot be established due to a lack of space in already developed areas. For an appropriate weighing of this problem planners must thoroughly concern themselves with the question of whether there is no other urban development concept or road traffic measure to produce relief.

The Traffic Noise Ordinance (16th Federal Immission Control Ordinance), which is to applied to the construction and major alteration of transport routes, represents a new aspect relevant for the weighing process in city planning. This ordinance and the immission limit values determined therein are valid regardless of the type of procedure selected for traffic planning and therefore also in connection with legally binding land-use plans provided that they contain the construction and alteration of a transport route. This determines both the requirements for noise abatement measures in the context of a legally binding land-use plan and the method of calculation which is to be selected in the case of a new road for example.

In the context of urban land-use planning, the requirements within the 16th Federal Immission Control Ordinance represent minimum requirements for the protection from "harmful environmental effects" whose non-adherence may necessitate noise abatement measures. The immission limit values within the 16th Federal Immission Control Ordinance are therefore not qualified for representing an urban development principle within the meaning of the targets specified in DIN 18005-1 (principle of precaution). As several calculation directives coexist, it is recommendable with regard to the legal significance of the 16th Federal Immission Control Ordinance to always use this ordinance or the underlying RLS-90 as a basis for the calculation of traffic noise also in the process of a legally binding land-use plan.

The contents of the 16th Federal Immission Control Ordinance are significant for the weighing of noise abatement measures as the immission limit values therein represent another threshold, that is to say the limit of reasonableness without further provisions, which is reached when the "acoustic orientation values" within Supplement 1 of DIN 18005-1 are exceeded. The range between the acoustic orientation value according to DIN 18005-1 Supplement 1 which must possibly be met pursuant to the polluter pays principle on the one hand and the immission limit value according to the 16th Federal Immission Control Ordinance on the other hand provides the municipalities, as long as the reasons are plausible, with enough scope to fix the required presentations and designations in the many cases where an intended residential development comes close to existing transport routes due to a lack of appropriate areas.

It is also principally conceivable that the limit values are exceeded as the scope of the 16th Federal Immission Control Ordinance does not cover the case of a development approaching an existing road and there is a wide range of possibilities for city planning. In the case of a newly planned residential area only special reasons could provide the arguments for a noise exposure beyond the limits of "harmful environmental effects" which could withstand the process of appropriate weighing.