SRM II
| The calculation method SRM II is part of the „Recommended interim computation methods“ according to ANNEX II of the EC-Environmental Noise Directive EU2002/49/EG-2002. The implementation of SRM II in CadnaA refers, therefore, primarily to the procedure described in the so-called EU-Interim Report INT-2003 and the EC-Recommendation L 212/49 VBEB-2003, and not to the original Dutch procedure SRMII-1996. |
The Dutch calculation method SRM II („Standaardrekenmethode 2“) calculates in octave band width and splits up the source into 2 or 4 sub-sources, located at different heights depending on the train category.
Dialog Railway (for SRM II): spectrum is linear, sum-level is A-weighted („Tot-A“).
Already within the calculation of emission, the portions of braking or not braking trains are distinguished. The emission level per unit length in octave band i is calculated by:
\(L_{E,i}^h = 10 \lg(\sum_{c=1} n * 10^{E_{nb,i,c}^h / 10}+\sum_{c=1} n * 10^{E_{br,i,c}^h / 10})\:in\:dB/m\)
Note
Since the „Number of Vehicles“ D/E/N refer to each daily period (and not per hour) the emission level LE also refers to that period.
with
- n: is the number of train categories using the railway line under consideration,
- \(E_{nb,i,c}^h\): is the emission term for non-braking units for train in each train category (c = 1 to n), in octave band i,
- \(E_{br,i,c}^h\): the emission term for braking units for train in each train category (c = 1 to n), in octave band i,
- and at assessment height h (h = {0; 0.5; 2; 4; 5} m, dependent on the train category).
The emission terms E calculate from:
- for braking trains:
\(E_{br,i,c}^h = a_{br,i,c}^h+b_{br,i,c}^h \log V_{br,c}+10 \lg Q_{br,c}+C_{bb,imc}\:in\:dB\)
- for non-braking trains:
\(E_{nb,i,c}^h = a_{i,c}^h+b_{i,c}^h \log V_c+10 \lg Q_{c}+C_{bb,imc}\:in\:dB\)
with
-
\(a_{i,c}^h,\:b_{i,c}^h\): emission terms for train category c in non-braking conditions, for octave band i, at height h (dB)
-
\(a_{br,i,c}^h,\:b_{br,i,c}^h\): emission terms for train category c in braking conditions, for octave band i, at height h (dB)
- Qc: mean number of non-braking units of the railway vehicle category concerned (h-1)
- Qbr,c: mean number of braking units of the railway vehicle category concerned (h-1)
- Vc: mean speed of passing non-braking railway vehicles (km/h)
- Vbr,c: mean speed of passing braking railway vehicles (km/h)
- bb: type of track/condition of the railway tracks (-)
- m: estimation of the occurrence of track disconnection (-)
- Cbb,i,m: correction for to track discontinuities and rail roughness (dB)
Train Classes
The existing categories provided in the Dutch emission database are differ by propulsion system and wheel brake system as follows:
| Category | Train description |
|---|---|
| 1 | Block braked passenger trains |
| 2 | Disc braked and block braked passenger trains |
| 3 | Disc braked passenger trains |
| 4 | Block braked freight trains |
| 5 | Block braked diesel trains |
| 6 | Diesel trains with disc brakes |
| 7 | Disc braked urban subway and rapid tram trains |
| 8 | Disc braked InterCity and slow trains |
| 9 | Disc braked and block braked high speed trains |
| 10 | Provisionally reserved for high speed trains of the ICE-3 (M) (HST East) type |
Train Units
The next figure shows side views of the train categories and specifies the number of individual units (i.e. locos, carriages or cars). One unit of any given category determines the sound emission. In the case of the trains drawn, the locomotives, carriages or cars act as individual units. In case of integrated passenger trains (category 9), each connected section (i.e. a railcar or a carriage) is regarded as a single unit.
SRM II-specific train categories (in brackets: number of carriages/cars per unit). For category 7 a single unit consists of a carriage with 3 bogies (i.e. 6 axles).
Note
In SRM II calculation method, the modification of the predefined train categories („train classes“) with regard to a real train composition with deviating train length, can just be corrected by using the number of units (i.e. locos/carriages/cars) within the periods D/E/N, but not by modifying the train length itself. The train length is not an editable parameter in SRM II.
Consequently, the figures „Number of Trains“ to be specified in CadnaA represent the number of individual units (locos/carriages/cars) within the periods D/E/N. For example, a high speed train of category 9 having 8 carriages and two railcars (locos) has to entered as
C09: 8
C09r: 2
With ten trains of this type passing during the daily period the input figures for column „Day“ would be:
C09: 80
C09r: 20
Emission Indices a, b
| category | octave band with centre frequency [Hz] | ||||||||
| 63 | 125 | 250 | 500 | 1k | 2k | 4k | 8k | ||
| index code | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | |
| 1 | a | 20 | 55 | 86 | 86 | 46 | 33 | 40 | 29 |
| b | 19 | 8 | 0 | 3 | 26 | 32 | 25 | 24 | |
| 2 | a | 51 | 76 | 91 | 84 | 46 | 15 | 24 | 36 |
| b | 5 | 0 | 0 | 7 | 26 | 41 | 33 | 20 | |
| 3 | a, v < 60 km/h | 54 | 50 | 66 | 86 | 68 | 68 | 45 | 39 |
| a, v >= 60 km/h | 36 | 15 | 66 | 68 | 51 | 51 | 27 | 21 | |
| b, v < 60 km/h | 0 | 10 | 10 | 0 | 10 | 10 | 20 | 20 | |
| b, v >= 60 km/h | 10 | 30 | 10 | 10 | 20 | 20 | 30 | 30 | |
| 3 motor | a, v < 60 km/h | 72 | 88 | 85 | 51 | 62 | 54 | 25 | 15 |
| a, v >= 60 km/h | 72 | 35 | 50 | 68 | 9 | 71 | 7 | -3 | |
| b, v < 60 km/h | -10 | -10 | 0 | 20 | 10 | 20 | 30 | 30 | |
| b, v >= 60 km/h | -10 | 20 | 20 | 10 | 40 | 10 | 40 | 40 | |
| 4 | a | 30 | 74 | 91 | 72 | 49 | 36 | 52 | 52 |
| b | 15 | 0 | 0 | 12 | 25 | 31 | 20 | 13 | |
| 5 | a, v < 60 km/h | 41 | 90 | 89 | 76 | 59 | 58 | 51 | 40 |
| a, v >= 60 km/h | 41 | 72 | 89 | 94 | 76 | 58 | 51 | 40 | |
| b, v < 60 km/h | 10 | -10 | 0 | 10 | 20 | 20 | 20 | 20 | |
| b, v >= 60 km/h | 10 | 0 | 0 | 0 | 10 | 20 | 20 | 20 | |
| 5 diesel | a | 88 | 95 | 107 | 113 | 109 | 104 | 98 | 91 |
| b | -10 | -10 | -10 | -10 | -10 | -10 | -10 | -10 | |
| 6 | a, v < 60 km/h | 54 | 50 | 66 | 86 | 68 | 68 | 45 | 39 |
| a, v >= 60 km/h | 36 | 15 | 66 | 68 | 51 | 51 | 27 | 21 | |
| b, v < 60 km/h | 0 | 10 | 10 | 0 | 10 | 10 | 20 | 20 | |
| b, v >= 60 km/h | 10 | 30 | 10 | 10 | 20 | 20 | 30 | 30 | |
| 6 motor | a, v < 60 km/h | 72 | 88 | 85 | 51 | 62 | 54 | 25 | 15 |
| a, v >= 60 km/h | 72 | 35 | 50 | 68 | 9 | 71 | 7 | -3 | |
| b, v < 60 km/h | -10 | -10 | 0 | 20 | 10 | 20 | 30 | 30 | |
| b, v >= 60 km/h | -10 | 20 | 20 | 10 | 40 | 10 | 40 | 40 | |
| 7 | a | 56 | 62 | 53 | 57 | 37 | 36 | 41 | 38 |
| b | 2 | 7 | 18 | 18 | 31 | 30 | 25 | 23 | |
| 8 | a | 31 | 62 | 87 | 81 | 55 | 35 | 39 | 35 |
| b | 15 | 5 | 0 | 6 | 19 | 28 | 23 | 19 | |
Emission Indices for category 9
| category | octave band with centre frequency [Hz] | ||||||||
| 63 | 125 | 250 | 500 | 1k | 2k | 4k | 8k | ||
| index code | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | |
| railcar (=loco) | |||||||||
| 9, 0 m | a | 7 | 14 | 57 | 52 | 57 | 66 | 47 | 71 |
| b | 27 | 28 | 12 | 18 | 18 | 15 | 21 | 5 | |
| 9, 2 m | a | 9 | 10 | 1 | 41 | 8 | 17 | 0 | 23 |
| b | 26 | 28 | 36 | 22 | 37 | 34 | 39 | 24 | |
| 9, 4 m | a | 5 | 11 | 13 | 56 | -27 | -19 | -37 | -12 |
| b | 27 | 28 | 31 | 15 | 50 | 47 | 53 | 36 | |
| 9, 5 m | a | 11 | 18 | 28 | 28 | -50 | -41 | -84 | -34 |
| b | 25 | 26 | 25 | 25 | 59 | 56 | 73 | 45 | |
| pushed/pulled units (=cars) | |||||||||
| 9, 0 m | a | 3 | 10 | 57 | 50 | 53 | 62 | 43 | 67 |
| b | 27 | 28 | 12 | 18 | 18 | 15 | 21 | 5 | |
| 9, 2 m | a | 3 | 10 | 57 | 46 | 47 | 55 | 37 | 61 |
| b | 27 | 28 | 12 | 18 | 18 | 15 | 21 | 5 | |
| 9, 4 m | a | 1 | 8 | 54 | 40 | 40 | 49 | 30 | 54 |
| b | 27 | 28 | 12 | 18 | 18 | 15 | 21 | 5 | |
| 9, 5 m | a | 3 | 10 | 54 | 0 | 0 | 0 | 0 | 0 |
| b | 27 | 28 | 12 | 0 | 0 | 0 | 0 | 0 | |
Breaking Correction
| octave band i | Cbrake.i.c(in dB) | |||
| cat = 1, 4, 5 | cat =2 | cat = 7 | cat = 3, 6, 8, 9 | |
| 1 | -20 | -20 | -8 | -20 |
| 2 | -20 | -20 | -7 | -20 |
| 3 | -20 | -20 | -20 | -20 |
| 4 | -2 | 0 | -20 | -20 |
| 5 | 2 | 1 | -20 | -20 |
| 6 | 3 | 2 | -20 | -20 |
| 7 | 8 | 5 | -20 | -20 |
| 8 | 9 | 5 | -5 | -20 |
cat: Train Category
Superstructure bb (Track Condition)
The correction factor Cbb,i as a function of structures above station compounds or railway track condition (bb) and octave band (i) is:
| octave band i |
Cbb,i (in dB) | |||||||
| bb=1 concrete sleepers in gravel |
bb=2 wooden sleepers in gravel |
bb=3 gravel |
bb=4 blocks |
bb=5 blocks and gravel |
bb=6 contr. rail fixation |
bb=7 contr. rail fixation + gravel |
bb=8 poured in railway lines |
|
| 1 | 0 | 1 | 1 | 6 | 6 | - | 6 | 5 |
| 2 | 0 | 1 | 3 | 8 | 8 | - | 1 | 4 |
| 3 | 0 | 1 | 3 | 7 | 8 | - | 0 | 3 |
| 4 | 0 | 5 | 7 | 10 | 9 | - | 0 | 6 |
| 5 | 0 | 2 | 4 | 8 | 2 | - | 0 | 2 |
| 6 | 0 | 1 | 2 | 5 | 1 | - | 0 | 1 |
| 7 | 0 | 1 | 3 | 4 | 1 | - | 0 | 0 |
| 8 | 0 | 1 | 4 | 0 | 1 | - | 0 | 0 |
Besides the track condition a roughness correction is applied which is a function of track disconnections. The wheel roughness depends on the type of brake system as a function of the wavelength (radiated frequency is speed related).
Note
The model of roughness correction applied in the original SRM II method is not dealt with here as it not included in the calculation of emission in both 2003/613/EC and in CadnaA.
Disconnections
The following types of disconnections are available:
- jointless rails
- rails with joints
- 2 switches per 100 m
- > 2 switches per 100 m
Speed (km/h)
SRM II indicates the following maximum speeds per category:
| category | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
|---|---|---|---|---|---|---|---|---|---|---|
| v [km/h] | 140 | 160 | 140 | 100 | 140 | 120 | 100 | 160 | 300 | 330 |
These train type specific speed limits are, however, not implemented in CadnaA for the time being.
When specifying a track-relevant maximum speed vmax the speed will be adjusted if necessary. In the calculation the smaller of both values is used.
Local Train List
Train Type
The SRM II specific train types are selected from a software internal list, i.e. the data not being available in the local or global libraries „Train Class“. This is due to the specific data structure not compatible with other railway noise standards.
Number of Trains Day/Evening/Night
number of units/vehicles D/E/N. For calculations for mixed evaluation parameters (such as Lden) see SRM II.
Speed v (km/h)
relevant speed of trains (km/h)
Percentage of breaking vehicles
percentage of all vehicles of a train category to be considered as braking vehicles
Note
The emission level LAE is not displayed in the dialog Train Class, but on the dialog Railroad (as not all correction factors are known with the dialog Train Class).