LESSON 1/TASK 1
Data is recorded as to how drivers complied with the signals. Field sheets may be produced locally.
Samples of such field sheets are in FM 19-25. The MP observing traffic record the number of vehicles
that enter the intersection on the three different colors. They also record which direction they turned, or
if they went straight ahead. This data may then be analyzed and compared with other information.
Intersections that have a high level of noncompliance, more than 4%, are considered problem
intersections. This information can be used for selective enforcement and/or to educate and inform the
public. It may also indicate that there may be a problem with the timing of the signals or some other
physical problem. For example, the sun at certain times of the day may reduce the visibility of the
signal.
Origin-Destination Studies
The PM is responsible for the installation traffic circulation plan. In order that traffic may flow as
smoothly and safely as possible, it may become necessary to collect data as to where the traffic came
from and where it is going. That is the purpose of this type of study. The information gathered may be
used to modify the circulation pattern or assist in other long range planning activities. These studies
are time consuming and rather complex. They also require the cooperation and assistance of the
public. There are five different methods of conducting origin destination studies that are outlined in FM
19-25.
Vehicle Occupancy Studies
Vehicle occupancy studies are often used in conjunction with volume studies. The study is conducted
by observing the number of people in each vehicle as it passes a given point. They can be used to
determine the need for car pools. The data can also be used in public information programs to
encourage the use of car pools and thus reduce traffic volume. They may also be used to determine
the need for mass transit, as well as parking facilities.
Speed Delay Study
A speed delay study is conducted by having an unmarked vehicle enter the flow of traffic during
different time periods. It then follows a prescribed route and notes the time it takes to get from one
landmark to another along the route. More than one vehicle can be used. The route is traveled
repeatedly and at different times. The results of
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