appendix a - Velocidade

22
The effect of speed on noise, vibration and emissions
from vehicles
May 1998
Table 4: Summary of pollution benefits from installation of TCS, (Metz et al 1997)
Pollutant Change in emission
CO -24%
CO2
-21%
HC -30%
NOx
-4%
Particulates -36%
Notes: Negative values indicate a reduction in emissions.
The results of this study indicate that the secondary issue of the environmental effects of
installing the TCS have matched the safety function in their effectiveness.
2.4 EMISSION MODELS
Emission models can be broadly divided into two categories:
• Microscopic
• Macroscopic
Microscopic models consider the individual characteristics of vehicles in terms of their
acceleration and speed at small time steps (typically less than a second). Detailed emissions
data relating to these characteristics are required.
Macroscopic models use parameters such as journey length and average speed to produce
estimates of emissions for a journey. Emission data, such as that collected during the
MODEM project, can be applied according to the most appropriate driving cycle and
average speed of the vehicles in the section considered.
This review considers models which are commercially available and attempts to assess their
relative merits. The SMARTEST DGVII Fourth Framework project has produced a review
of current micro-simulation models (Algers et al., 1997) which contains more in depth
reviews of the modelling capabilities of some of the simulations discussed in the Appendices
A and B of this report.
2.5 EMISSIONS DATABASES
Three large European databases of emissions data have been identified. The MODEM (Jost
et al 1992) and HEB (see Shearn et al. 1997) databases appear more suited than CORINAIR
(Eggleston et al 1989) to the environmental assessment of schemes based on changes to the
speed profiles of vehicles travelling through the schemes. In developing an assessment tool,
it is recommended that the results from one or more of the above databases are used in
conjunction with or compared against the results of the micro and macroscopic models
which have been identified. These databases are described in Appendix C.