TNM

Note - The Federal Highway Administration Traffic Noise Model (FHWA TNMTM) is protected by U.S. copyright laws. The noise prediction methodology used in CadnaA has been designed to be consistent with version 2.5 of TNM. However, CadnaA has not been tested, evaluated, or approved for use by any Agency of the U.S. Government.

Emission Parameter

The emission parameter in TNM 2.5 („Traffic Noise Model“) is the A-weighted level L_traf,ref in dB(A) at a distance of 50 ft. (15.24 m) perpendicular to the axis of a road with infinite length with absorbing flat ground TNM-2.5.

In TNM, emission is based on A-weighted levels (expressed in energy form), while sound level computations use one-third octave-band data, converted to A-weighted levels for display and output.

Dialog Road (for TNM)

Vehicle Categories

The vehicle categories and their definitions available in TNM are listed in the subsequent table.

Note

For the time being, CadnaA does not allow for user-defined vehicle categories.

TNM-vehicle categories	Definition
autos	all passenger cars (2 axles, 4 tires), gross mass < 4500 kg (< 9900 lb)
medium trucks	cargo vehicles (2 axles, 6 tires), 4500 kg < gross mass < 12000 kg (9900 lb < m < 26400 lb)
heavy trucks	all cargo vehicles with 3 and more axles, gross mass > 12000 kg (> 26400 lb)
buses	all vehicles (2 or 3 axles) designated for transportation of 9 or more passengers
motorcycles	all vehicles with 2 or 3 tires with an open-air driver and/or passenger compartment

Emission Scheme

The emission for each category, pavement type and throttle setting, is represented by 17 constants (2*7+3=17, resulting in 17*(5*4*2)= 680 constants in total) applying the following equations.

The radiated energy E_A is:

$E_A(s_i)=(0.6214*s_i)^{A/10}+10^{B/10}+10^{C/10}$

converted to A-weighted levels per third-octave band:

$L_{emis,i}(s_i,f)=10 \lg E_A+\sum_{j=1}^{7}(X_1+0.6214*X_2*s_i)*\lg f^{j-1}$

with

$(X_1;X_2)=\{(D_1;D_2), (E_1;E_2),...,(J_1;J_2)\}$

with

s_i speed of vehicle type i (in km/h)
A1...J1, A2...J2 constants (see table 5 in TNM-1.0)
f frequency (in Hz)

Converted back to its energy form:

$E_{emis}(s_i,f)=10^{L_{emis,i}/10}$

The emission level L_traf,ref is not displayed in the TNM 2.5 software. Instead, the emitted energy E for each vehicle category can be exported to a csv-file using the procedure described below:

locate the file tnm.ini in C:\WINDOWS
open the file and add the section:

[Diagnostics]
emission=1

with each TNM-calc run a file emit.csv is written besides the .dat and .idx files
emit.csv lists the energy parameter E for each category and sub-source type
sum E for all categories and sub-source types gives after conversion

Specification of Emission

MDTD

CadnaA offers to introduce traffic data based on Mean Daily Traffic Data (MDTD), though not available in the original TNM. In this case, the number of vehicles per hour and the percentage trucks/buses is calculated according to the specifications in the Austrian road noise standards RVS 3.02 RVS-1997 and RVS 4.02 RVS-2006.

Note

For details (and tables) on the traffic count (veh/h) and proportion of heavy vehicles (%) for each type of road see Nordic Prediction Method 1996, MDTD.

In this case, the percentages of motorcycles and of heavy trucks and buses are, however, 0% for all road types as those vehicles types are not considered in the Austrian road noise standards RVS 3.02 and 4.02.

Exact Counts

This option enables to enter counts for the five TNM-specific vehicle types, comprising autos (cars), medium trucks, heavy trucks, buses, and motorcycles. As traffic data in TNM is specified in absolute figures for each vehicle type, while CadnaA uses - as the majority of road noise standards do - a scheme based on hourly overall traffic and percentage, the following transformations apply to convert absolute figures:

Input data	CadnaA Attributes	calculates from TNM-input data according to ...
number of vehicles/hour	MT, ME, MN	$n_{\text{autos}}+n_{\text{Medium Trucks}}+n_{\text{Heavy Trucks}}+n_{\text{Buses}}+n_{\text{Motorcycles}}=n_{\text{tot}}$
Percentage of Trucks/Buses (%)	PT, PE, PN	$(n_{\text{Medium Trucks}}+n_{\text{Heavy Trucks}}+n_{\text{Buses}})/n_{\text{tot}}*100\%$
Percentage of Motorcycles (%)	PLAT, PLAE, PLAN	$n_{\text{Motorcycles}}/n_{\text{tot}}*100\%$
Percentage of heavy vehicles: Heavy Trucks (%)	PLT, PLE, PLN	$n_{\text{Heavy Trucks}}/(n_{\text{Medium Trucks}}+n_{\text{Heavy Trucks}}+n_{\text{Buses}})*100\%$
- Percentage of heavy vehicles: Buses (%)	PLLAT, PLLAE, PLLAN	$n_{\text{Buses}}/(n_{\text{Medium Trucks}}+n_{\text{Heavy Trucks}}+n_{\text{Buses}})*100\%$

Note

A scheme using hourly traffic and percentages has the advantage that overall traffic figures can be changed without altering the traffic mix.

Example

Path: Examples\Sources\Road\Road\Calc CadnaA-figures from TNM-figures.xls

Ltraf,ref dB(A)

direct input of L_traf,ref in dB(A)

Diurnal Pattern

see Common Input Data, Diurnal Pattern

Source Geometry

Depending on vehicles type, sub-sources are located at different heights (at 0.1 m for tire, 1.5 m (5 feet) for engine, and 3.66 m (12 feet) for stack, all above ground).

Note

A height of 0.1 m for the tire source as in TNM 2.5 software is used, while the TNM 1.0 documentation states a height of 0.0 m instead.

Speed Correction

Traffic speed can be specified for "Autos" and - if activated - for "Trucks" separately (in km/h). The speed limit entered for "Autos" will be considered as limit for autos and motorcycles, while the speed limit entered for "Trucks" - if any - will be considered for medium and heavy trucks, and for buses. With the limit entered just for "Autos" (i.e. "Trucks" deactivated) the value applies to all types of vehicles (no intrinsic speed limit for trucks).

Note

Accelerating ramps and flow control devices are not available in CadnaA for the time being.

Button DEN

see Common Input Data, Button DEN

Road Surface

The following TNM-specific road surface types are available:

Attribute Value STRONR	Road Surface Type	Explanation
1	Average	i.e. average of DGAC and PCC
2	DGAC	dense-graded asphaltic concrete
3	OGAC	open-graded asphaltic concrete
4	PCC	Portland cement concrete

Note

FHWA states that the „average pavement type shall be used in the FHWA TNM for future noise level prediction unless a highway agency substantiates the use of a different pavement type for approval by the FHWA.“

Throttle

TNM has two kinds of operating conditions causing a different emission: „cruise throttle“ and „full throttle“. With the option „Throttle“ activated the respective road will be considered as a full throttle road.