A direct noise load of Metro 4 under construction will be experienced near the future stations, and in the phase of operation near the ventilation installations of stations and running sections, as well as around the depot. In the period of construction a direct noise effect appears along the routes used by transport vehicles, then following the putting into operation practically in the whole Capital City a positive change in noise pollution can be expected.
In respect of the direct noise influence of Metro 4, limit values provided in decrees should be fulfilled, which are more severe for the night period than for daytime. The limit values of construction noises depend also upon work duration; higher daytime noise levels are acceptable in the most noisy construction phases not taking more than one month in time, but night level requirements will be strict. The indirect noise impacts (caused by the change of the existing traffic) can be assessed on the basis of changes rather than on the basis of limit values.
Noise impact of constructions
As for the noise impact of Metro 4, the highest load on the environment and population is expected in the period of construction.
At the same time, when summing up noise protection issues it definitely confirms the concept that the noise emission of construction works can be maintained within acceptable limits by:
- Selecting an environment friendly building technology,
- Restricting surface works to as short as possible, then by proper screening of the construction site,
- Using up-to-date machines and installations with the lowest possible noise emission,
- Individual noise reduction of building machines,
- Acoustically delimiting the construction site (by decreasing noise loads),
- a számottevő zajkibocsátással járó munkák időbeli szabályozásával
- Regulating the duration of the works associated with considerable noise emission.
- However, unexpected situations can emerge because of technological, technical or safety reasons (which may or may not be forecast in design, but cannot be prevented), when limit values exceed admitted levels.
In such situations, special authorisation of the environment protection authority is required to approve exceeding limit values. In the application for such an authorisation the foreseen duration and extent of exceeding limits should be specified, the necessity of the activity causing higher limit values shall be justified, then the instructions, stipulations of the possibly obtained authorisation shall be fully observed. Of course, in the design of construction works one should intend to restrict such situations to the absolutely exceptional cases. With this in mind, exceptional care should be taken to the construction of stations that are located directly near residential areas (e.g. stations Bocskai út, Szt. Gellért tér, Fővám tér, Kálvin tér).
Direct impact of the operation
Concerning direct noise impact along metro route, only noise emission of ventilation installations need special attention.
These installations provide for two kinds of ventilation:
- Ventilation of tunnels and
- Ventilation of stations.
- The installation of ventilation of stations is equipped with acoustic absorbers both on the suction and the delivery side. By means of such noise reduction measures it is possible to maintain the limit value of 55 dB provided for the area of stations, as well as to restrict surface noise emissions overnight to 45 dB.
It is the motion of vehicles in the depot that can represent a considerable noise source concerning the noise load of this impact area, also possibly including some repair, washing and auxiliary activities.
The trains getting in and out of the depot usually move by a speed of under 30 km/h, thus, the resulting noise load can be under limit values.
A proper reduction of the noise emission of technological (mechanical equipment) and building engineering installations can definitely be satisfied by means of technical / architectural solutions, thus, the environmental noise emission of the depot is in agreement with noise protection requirements.
Indirect impacts to be expected
In the period of metro construction there will be no considerable increase in noise emission not even along the route used by material transporting freight vehicles, there will be a change within just 0.5 dB.
The increase of noise loads resulting from traffic change in the period of construction will not be significant, however, in order to release Pterffy S. utca and Garay utca, further diverting roads are suggested.
As a direct noise impact of the metro operation, only the noise load changes of transport origin related to traffic change should be discussed (out of a noise protection viewpoint).
Transport-related noise in the area concerned (except maybe for few roads) is higher than acceptable both at day and night.
Noise load is especially too high (daytime >74 dB, overnight >67 dB) around Budarsi t, Nagyszls utca, Bartk Bla t, Kossuth L. utca, Rkczi t, Kerepesi t, Mzeumkrt., Vmhz krt., Kroly krt., Hegyalja t, Ferenc krt., Alkots utca, Bajcsy Zs. t, Festetics Gy. t, Thkly t. In the areas listed, noise load is mainly a consequence of the intense traffic, and secondarily that of the high building density.
On a long term, an increase of the noise load by 0 to 4 dB with respect to the existing status could be expected (due to transport increase) in the area investigated. This means that the already rather high noise load could further increase.
Following the construction of Metro 4:
- An increase of the noise level by more than 2 dB is forecast along Rimaszombati út and Hamzsabégi út.
- A decrease of the noise level by more than 2 dB can be expected in Budafoki út and Fadrusz utca.
Noise level will increase in several streets only in a hardly perceptible manner (just theoretically), and in general it will not change in the most part of the area concerned.
At the same time, Metro 4 will result in a reduction of noise level in the over-congested area in Buda and the City centre (most of Budapest's territory) with high noise load, high building density with multi-storey residential and institutional buildings, which will not be considerable, but still relevant.
Thus, the effects of the Metro line out of noise protection viewpoints are significant, since the noise condition of areas with high noise level and building density may improve, mostly ensuring reduction where it is the most needed, while no other methods can yield such results.