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Recommendations for Planning . |
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6.3.3 Traffic Traffic Planning Traffic planning measures such as the exclusion of through traffic from residential areas, bypass roads to relieve encumbered thoroughfares, speed limits, and support of public transit all contribute to the reduction of air pollution. The connection between speed limits and emissions produced by vehicles is dealt with in Section 2.8.2 Figure 6/25 emphasizes the criteria for traffic-calmed urban zones; namely, the bundled functioning of primary streets with bordering, shielding buildings and subterranean parking enclosures. Since limitations
of building use are to be expected in the vicinity of
heavily-trafficked roads, the planning or the corresponding site
plan establishment of roads with traffic counts higher than
10,000 vehicles/hour requires a report on the exhaust immissions
level for the areas near the road. The tools available for
immissions prognoses are explained in Sections
4.3.4 to 4.3.7. Evaluation of Exhaust Immissions Levels For the evaluation of calculated pollution levels on roads and their nearby areas, the previous pollution levels as well as the intended uses in the vicinity of the road are important. In the case of a planning situation in an existing central-city traffic network, one may come to a different evaluation than in the case of a planning situation for a new residential area and roads – for instance in the course of a future local bypass. The precaution threshold values published by the WHO should be employed especially for evaluations in the planning of new residential areas (cf. Section 2.9). Exceeding the immissions values of the TA Luft
or the 22nd BImSchV (Ordinance for Immissions Values)
can potentially come into consideration, however, as serious
air-hygienic findings in the context of zoning and planning.
Threshold value excesses in a planning area are thus possible in
justified cases. It must nevertheless be noted which measures
could be used to reach an improvement (both inside and outside
the planning area). A planning decision for future residential
use is, however, usually questionable under these circumstances. A likewise high level of pollution is marked by the so-called test values of the 23rd BImSchV (Ordinance for Concentration Values). Since the review of traffic-planning, traffic-redirecting, or traffic-limiting measures is supposed to eliminate the exceeding of these concentration values according to § 47 (2) BImSchG, healthy residential conditions in these areas must be considered. On the other hand, the law relates the redevelopment order expressly to road traffic, so that building and zoning restrictions for the adjacent uses do not have to be produced from the definition of the test values. When considering allowing residential use that is to be maintained or developed further in special residential areas (WB) or that is desired for city stimulation, the values of the 23rd BImSchV are, however, to be considered in every case in view of the required planning measures. . Immissions-Reducing Influences The pollutant concentrations caused by traffic typically decrease strongly with increasing distance from a road. This reduction is also the case (with conditions) for nitrogen dioxide. Since the noise pollution from a road also decreases with distance, sensitive uses (e.g. residential, recreation, etc.) should be secured with corresponding protective distances so that both the noise protection requirements and the immissions criteria from TA Luft and the 22nd and 23rd BImSchG are maintained as minimum requirements. In street canyons with buildings lining the road, there is no possibility for protective distances. Immissions protection mechanisms such as noise protection barriers and walls as well as dense plantings are quite effective remedies against exhaust pollution. Enclosed peripheral development produces a substantial reduction in pollution on the side of the buildings facing away from the street as well as in the area behind the buildings. As a rule, lower pollution levels are also present near the upper floors of peripheral buildings compared with the lower. To that extent, the possibility exists for allowing residences when limited to certain floors along main traffic streets. . Plantings as Immissions Protection The reduction in pollution through plantings of trees and shrubs occurs both through the filter effect of the plants themselves (i.e. their large effective surface area), which affects especially powder-forming pollutants, and through the alteration of the wind field from the plants. Wind tunnel studies (BRILON et al., 1987; ROMBERG, 1988) have indicated that, in order to obtain equally advantageous effects on the immissions situation of particles and gases, a broad planting (>10 m wide) is necessary, which creates intermediary space for wind to pass through. A mixed planting of leafy and coniferous trees is recommended, as depicted in Figure 6/26. The influence of
plantings on the improvement of the immissions situation with
pollutants on roads thereby distinguishes itself from the
possibility of reducing sound levels with vegetation along roads
(STAEDTEBAULICHE LAERMFIBEL, 1994). Legal Bases (Pollution Control) According to § 9 (1) 24. BauGB, a site plan can establish "protected areas to be kept free of development, areas for special facilities and precautions for protection from harmful environmental effects in the sense of the Federal Pollution Control Law, as well as for protection from such effects, or for avoidance or reduction of such effects from built and other technical precautions." According to § 9 (5) 1. BauGB, areas should be denoted in a site plan whose development would require special built precautions against external effects. Example of a regulation in accordance with §
9 (1) 24. BauGB: Another example regulation: Notation: |
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| Fig. 6/25: Traffic planning measures | |
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| Fig. 6/26: Planting of leafy and evergreen trees. A reduction of roughly 60% in immissions is generally possible. Very good filtering of dust in summer and winter. No increase of gaseous immissions in winter due to the mixed planting of evergreen and leafy trees; Source: MLuS-92 | |
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