Environmental Engineering Reference
In-Depth Information
boot space of the vehicle with rubber foam used to provide shock dampening as
experience by
[20]
. Both sample lines were 2.66 m long, and made from an appro-
priate anti-static material to minimize the effect of the tubing walls
[20]
. The sample
line for internal measurements was threaded through the left corner of the parcel
shelf and the inlet was located within the breathing zone of the front passenger, and
fixed to the headrest. The sample line for external measurements was threaded
through the right corner of the parcel shelf and passed through the partially open rear
driver-side window and secured to the roof rack assembly using zip ties, 155 cm
from the road surface with the inlet directed forward. The rear window was sealed
using adhesive tape, and the lines secured with care being taken to avoid kinking.
The standard set up for ventilation inside the monitoring vehicle was as follows;
windows closed, vents open, fans set to 'recirculate' (level 2 setting) and air condi-
tioning off. To discount obvious non-combustion sources of particles both driver and
passenger were instructed not to make excessive or abnormal movements, which
could re-suspend dust particles from within the seats. As this was a fleet vehicle
there was no need to consider issues associated with smoking identified by
[21]
.
After each run the boot and all doors were opened to ventilate the car and bring
the internal environment back to background.
The route (Fig.
2
) chosen for this study was 4.2 km long and was selected to
facilitate efficient passage through both the east and westbound bores of the
Westgate tunnel whilst also providing a suitable location to stop and pre-condition
the cabin before each run. This was a small lay-by (marked as A in Fig.
2
) behind
a car park. All measurements from within the tunnel were taken from the right-hand
lane as it had been identified that pollution concentrations varied with distance across
the carriageway
[22]
. As well as the tunnel microenvironment, the route encountered
other urban highway features such as; open carriageway, covered carriageway
(bridges), slip roads and two busy gyratories.
Results and Discussion
Sampling was conducted on Tuesday 26th and Wednesday 27th June 2007, with
07:30-09:30 and 12:30-14:30 representing the peak and inter-peak periods respec-
tively. The duration of each sampling period was limited to 2 h as this was a con-
servative estimate of the lifespan of the battery powering the onboard computer
hardware. A total of 21 trips were completed, with 11 carried out during the peak
period and ten during the inter-peak period. All particle number counts (PNCs)
were measured in particles cm
−3
.
External concentrations:
Figure
3
shows external PNCs as recorded by the CPC
measuring air at the roof rack of the car. PNCs are presented in four groups; the first
group of data indicates averaged concentrations for the whole route, while the
second set indicated concentrations for the non-tunnel part of the route; and lastly
the third and fourth sets present concentrations in the East and West bores of the
tunnel. Concentrations in each set are separated for peak and non-peak periods.
