
7-5
The TDC Ultra is waiting for you to push a Count or Gap button, which
starts the study. The display in the lower left corner shows the current
time, so it is easy to synchronize the start of the study to the beginning
of the desired interval. You do not have to push the first button exactly
when the seconds roll over to zero. The analysis software rounds the
start of the count to the nearest minute automatically. However, when
starting a new study, always try to begin as close to an interval bound-
ary as possible, such as xx:00, xx:15, xx:30, or xx:45.
Press either a Count key or a Gap key and the TDC Ultra will begin
recording data.
When you push the first button
to start the study, the display
changes to show the amount of
time left in the present interval.
In this case, it starts at 15:00
minutes and counts down to
zero. At the end of each interval, the TDC Ultra beeps three times.
Normally you are not watching the display, you are watching the traffic.
The beeps remind you that the interval is over. This is only important if
this is the last interval and you are ready to quit; otherwise, just ignore
the beeps and keep counting vehicles.
There is no data stored in the counter until after the first interval. If, after
starting a study, you realize that you set one of the parameters wrong,
you can turn off the TDC Ultra and restart the study correctly. However,
once an interval has finished, the study is stored in memory. So, if you
realize after the first interval that you have made a mistake, you need
to either make a note to the person downloading the data to ignore that
study, or clear the TDC Ultra’s memory, as described on page 2-9.
The second and third lines of the display also change. They show each
direction with the current count values (N) and the times in seconds of
the current gap being measured (Gap).
Collecting the gap data is very easy. Imagine a line across the road
or lane that you want to measure. Press the Direction 1 GAP key (see
template on page 6-2) when a gap starts, i.e. the end of a car just passed
over the line, and there isn’t a car immediately behind it. Hold the button
Gap Study Int:001
Dir 1: N=002 Gap=00
Dir 2: N=004 Gap=00
08:01:23 Rem 13:37
Chapter 7 — Multi-direction Gap Studies
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