Ultra Start 15xx Bedienungsanleitung PDF herunterladen (Seite 71)

8-3

This manual does not attempt to explain what is meant by terms such as

saturation ﬂow rate, or arrival type. If you are not familiar with the terms

then you should consult a reference such as the Highway Capacity Manual,

published by the Transportation Research Board.

The procedure implemented in the TDC Ultra is based on accurately mea-

suring the time that events happen. This contrasts with most of the other

studies in the TDC Ultra which are based on counting the number of events

that happen in a relatively long time period. The events are timed to a res-

olution of 15.6 milliseconds. To perform this study correctly you have to

press the proper keys at exactly the right times.

Saturation Flow Rate studies are done at one approach to a signalized in-

tersection. You normally are interested in the critical lane or lanes, which

usually are the through movement(s). You can also measure Sat Flows for

a left turn lane as a separate study.

Your position at the intersection is very important as you need to be able

to easily see three events:

1. Phase changes on the signal.

2. Cars entering the intersection. You press keys when vehicles pass

over the stop bar as they enter the intersection.

3. Cars stopping during the red phase of the light.

The diagram below shows the position we recommend for doing the data

collection, although you can position yourself anywhere you feel we let

you easily observe the three events described above.

When you are in a good position, you are ready to start the study.

Chapter 8 — Saturation Flow Rate Studies

STOP

Stand Here

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Ultra Start 15xx Bedienungsanleitung Seite 71