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5-3

The TDC Ultra uses the term Classiﬁcation primarily for vehicle classi-

ﬁcation studies, but not exclusively. With the TDC Ultra, you can do three

types of classiﬁcation studies:

1. Vehicle Classiﬁcation using the Federal Highway Administration’s

vehicle classiﬁcation system (scheme F).

2. Vehicle Classiﬁcation using your own scheme.

3. Any type of classiﬁcation study you invent.

The ﬁrst two are very similar. They both involve assigning a vehicle type

to each button. The FHWA scheme F uses 13 different classes of vehicles,

based on the number of axles and the spacing of axles. It is designed to

be compatible with automatic trafﬁc counting equipment using road tube

sensors, such as the JAMAR TRAX series. Road tubes can only measure

the presence of an axle, so the automatic counters can only count axles and

measure the spacing between axles. The FHWA Scheme F does a good

job of discriminating most types of vehicles, but because it is designed

for automatic data collection equipment, it suffers from some limitations

when applied to manual counts. For example, it often is difﬁcult to tell at

a glance whether a truck has 5 or 6 axles, while it is easy to see the differ-

ence between two small cars following one another closely and a four axle

truck, a situation which often confuses automatic classiﬁers.

Manual classiﬁcation schemes can use criteria other than axle number and

spacing. With the TDC Ultra you can design your own scheme using up to

48 different types of vehicles. You can also deﬁne schemes in 2 or 3 direc-

tions with up to 16 classes per direction. In these cases, each key on the

TDC Ultra can be a different class, and multiple directions are classiﬁed by

using the BANK keys. For example, Key 9 might be a city bus. If the bus is

going north, you just press Key 9, if a bus is going south you press BANK1

and Key 9. In this way you can do a bi-directional study.

A common User-Deﬁned scheme is to have 4 vehicle types deﬁned: bikes

& motorcycles, cars, trucks, & buses. Four approaches to an intersection

can be counted with one counter without using the BANK switches.

The third type of classiﬁcation study supported by the TDC Ultra is a User-

Deﬁned study that can have any kind of classiﬁcation criteria, and count

Chapter 5 — Classiﬁcation Studies

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Ultra Start 15xx Bedienungsanleitung Seite 49