TRAFFIC STUDIES (CH.4) Flashcards
(28 cards)
is the most basic data needed for any traffic studies
TRAFFIC VOLUME
are conducted to obtain factual information on the number of vehicles and/or persons that pass at a specified point on the highway system.
Volume Studies
Types of Volume
- Annual Traffic
- Annual average daily traffic
- hourly traffic
- short-term count
is used for determining annual travel, estimating expected highway user revenue, computing accident rates.
Annual Traffic
is used for measuring the present demand for service by the road, programming capital improvements.
Annual average daily traffic (AADT)
is used for evaluating capacity deficiencies, geometric design or improvement of streets and intersections.
HOURLY TRAFFIC
is used to estimate maximum flow rate and determine the characteristics of peak hour volumes.
SHORT-TERM COUNT
Tapes of Data Collected
- MID-BLOCK COUNTS
- DIRECTIONAL COUNTS
- TURNING MOVEMENT OR INTERSECTION COUNTS
- CLASSIFICATION COUNTS
- CORDON COUNTS
- SCREEN LINE COUNTS
are used for preparing traffic flow maps and determining trends
MID-BLOCK COUNTS
are used for determining directional distribution for capacity analysis,
signal timing, justifying traffic control, etc.
DIRECTIONAL COUNTS
are used for signal timing, designing or
improving geometry of intersection, planning turning prohibition, analyzing high
accident intersections.
Turning movement or intersection counts
are used for determining modal split, estimating effects of heavy
vehicles on capacity, determining correction factors for automatic counts.
Classification counts
are used to determine the number of vehicles and/or persons entering and
leaving an enclosed area.
Cordon counts
are classified counts taken at some points along a line that bisects a given area.
Screen line counts
Abnormal conditions are usually avoided unless the purpose is to obtain information
concerning those conditions. These would include
a. special occasions such as public holidays or fiestas
b. days with abnormal weather conditions
c. strikes or demonstrations.
This is the simplest and sometimes most practical in the absence of any mechanical or automatic counting device.
By tallying
is a mechanical device useful when volume is high. Counters may he of single or multiple type.
manual counter
When traffic count of very long duration is required, automatic counters through
the use of detectors may be used
Using automatic counters
may be used to take footage of the traffic flow
video cameras
has been a common measure of daily traffic at a given location
annual average daily traffic or AADT
ADT is obtained by conducting traffic volume counts over a number of days at least ___ days and less than _____ days.
2days, 365days
The period during which speeds are measured depends on the purpose of the study.
time of study
When such instrument is available, the use of radar is very convenient way of conducting spot speed studies.
Radar speed meter
A very useful and less expensive way of conducting spot speed studies is called the
trap length method
