User`s manual

TDC Ultra User’s Manual
11-4
Preparing to do a
Roundabout Movement Study
Before you start a standard turning movement study, you must ask
yourself the following questions.
• Are the Bank 1 and Bank 2 keys going to be used?
• Can one person do the study, or will it require two or more, using
separate TDC Ultras?
• How is the TDC Ultra going to be oriented?
The answer to these questions depends on the experience of the people doing
the studies; there are no simple rules of thumb we can give you to help you
decide. The important thing is to use your knowledge of the people doing
the data collection, along with your experience with the traffic they are likely
to see in the field, to decide in advance what the best strategy would be.
Deciding on how the TDC Ultra will be oriented during the study depends
on where you will actually be located while doing the count. When the data
from the unit is downloaded to our software, the program assumes that the 1
through 4 keys were for the from north (southbound) approach, and the rest
of the keys are assigned accordingly. The TDC Ultra’s Roundabout overlay
has a North Arrow which suggests that you align the counter so that buttons
1 though 4 faces north while you are doing the count. It is not necessary to
always conform to this practice. Sometimes it is more convenient for you
to face another direction when you do the count, especially if you want to
be able to read the display.
The analysis software allows you to select which button was facing north
during the count; it just defaults to button #3. We recommend that (if pos-
sible) you use the default direction, since it eliminates one source of error
when you do the analysis. If you don’t use the default direction, it is im-
portant to note this. If you keep good notes in the field, you won’t have any
problems, no matter which way the TDC Ultra is aligned.