Traffic studies Flashcards
(46 cards)
the most basic data needed for any traffic studies.
Traffic volume
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
a. Annual daily traffic/Annual traffic
b. Annual average daily traffic (AADT)
c. Hourly traffic
d. Short-term count
used for determining annual travel, estimating expected highway
user revenue, computing accident rates.
obtained by conducting traffic volume counts over
a number of days at least two days and less than 365 days.
Annual traffic
used for measuring the present demand for
service by the road, programming capital improvements.
Annual average daily traffic (AADT)
used for evaluating capacity deficiencies, geometric design or
improvement of streets and intersections.
Hourly traffic
used to estimate maximum flow rate and determine the
characteristics of peak hour volumes.
Short-term count
Types of Data Collected
a. Mid-block counts
b. Directional counts
c. Turning movement or intersection counts
d. Classification counts
e. Cordon counts
f. Screen line counts
used for preparing traffic flow maps and determining trends.
Mid-block counts
used for determining directional distribution for capacity analysis,
signal timing, justifying traffic control, etc.
Directional counts
used for signal timing, designing or
improving geometry of intersection, planning turning prohibition, analyzing high
accident intersections.
Turning movement or intersection counts
used for determining modal split, estimating effects of heavy
vehicles on capacity, determining correction factors for automatic counts.
Classification counts
used to determine the number of vehicles and/or persons entering and
leaving an enclosed area.
Cordon counts
classified counts taken at some points along a line that bisects a
given area.
Screen line counts
The time and duration of a traffic volume study depends on the type and application of the
data to be gathered. Some of the typical counts are as follows:
a. Twenty-four-hour counts from midnight to midnight
b. Sixteen-hour counts from 6 AM to 10 PM to represent most of daily flow, including evening
traffic
c. Twelve-hour counts from 6 AM to 6 PM to cover most of daytime traffic
d. Peak period counts from 7 AM to 9 AM, 5 PM to 7 PM, or other time intervals corresponding to
very high level of traffic volume
e. Short counts of about one hour or less with intervals of 5-15 minutes to analyze
characteristics of peak hours.
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.
Methods of volume studies
A. By tallying
B. Using manual counters
C. Using automatic counters
D. Using video cameras
This is the simplest and sometimes most practical in the absence of any mechanical or
automatic counting device.
Tally sheets are used to record the number of vehicles.
The method may be
used when traffic volume is generally low or when observing a particular turning movement whose
volume is relatively low.
tallying
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, ____________ through
the use of detectors may be used.
automatic counters
The simplest type of an automatic counter is a
___________ laid transversely across the road.
More sophisticated detectors make use of ultrasonic waves or
inductance loops.
pneumatic tube
may be used to take footage of the traffic flow.
Video cameras
Presentation of Traffic Volumes
a. Variations
b. Flow Maps
c. Intersection Diagram
has been a common measure of daily traffic at
a given location. At a given point along a particular highway, it is estimated as the total volume
counted over one year divided by the number of days in the year,
annual average daily traffic or AADT
