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Back to the Traffic Count Map
Table of Contents
Please let us know if the questions and answers are helpful and if you found
the answer to your question. To forward a comment or question to the
staff e-mail your questions to atb@tricon.net.
What is the definition of "ADT"?
ADT stands for average daily traffic. On any given day this would be the
average number of vehicles traveling on a particular road. Back to top
How is traffic count data collected?
Vehicles are counted by the Tennessee Department of
Transportation (TDOT) in all 95 counties in Tennessee, each year.
Mechanical traffic counting devices are deployed along the roadside
(usually secured to a utility pole) and a rubber “road tube”
is placed across each traffic lane. Pressure from vehicles
crossing the rubber tube is detected by the mechanical counter (a small
box comparable in size to a car battery) and electronically stored by
the counter. The “road tube counters”
are placed on a section of highway for a minimal 24-hour period then moved to
another location. The collected data is then sent to TDOT central
offices in Nashville
for processing. The raw counts are then adjusted using a formula to
calculate the Average Daily Traffic. This
adjustment takes into consideration weekday and time of year variations.
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What are the counts used for?
Traffic count data is used by state and local
transportation officials in the planning of road improvements and
monitoring of traffic conditions. In the private sector - realtors,
bankers, developers, economic development agencies, as well as
citizens also use traffic count data for a a variety of purposes. This
information is provided via this web site as a service from the
Tennessee Department of Transportation in partnership with the
University of Tennessee Transportation Center and the Johnson City MPO.
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How often will the counts be updated?
As mentioned earlier, TDOT has an established
program for counting traffic in each Tennessee county every
year. In the Johnson City area this is usually done in the fall (October
or November),
depending upon the statewide schedule. By the time the data is
processed and transmitted back to the MPO staff, sometimes a new calendar year has
started. So the counts may have taken in November of 2002 would
likely not be ready for web posting before spring or summer of 2003.
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What is a traffic count station?
TDOT has 186 annual count locations in Carter and Washington Counties
for which data is obtained and monitored. A traffic count station
is a designated location for traffic data to be collected each
year. The numbers on the map indicate station numbers from the
Tennessee Department of Transportation's numbering system. The detailed traffic sheets have a street name or
highway number along with 2 intersecting roads to help you locate that
station. The table also includes the individual station numbers
listed below the map if the map link to the data is not working
properly. Back to top
Why do the traffic counts seem to vary so much from year to
year?
The traffic counts only indicate traffic detected during the week the
counters were placed at a given location each year. During the
course of a year most roadways experience a range of values depending
upon land use activities in the area. The counts for a given year
may be affected by road closings or detours from another route or a
variety of conditions that may occur. A more important indicator
of long term traffic patterns would be the trend line located at the
bottom of the information page. Variations of 10% to 20% of
an increase or decrease would not be uncommon from year to year.
The Johnson City counts are taken when East Tennessee State University
is in session which is an important factor in local and regional travel
patterns. The Johnson City MPO staff is working on an
Intelligent Transportation Systems project in which permanent electronic
count equipment will provide automated counts at several key locations
continuously for ongoing traffic monitoring purposes. Back
to top
Why is data not provided for some locations shown on the map?
Traffic counts are provided to the MPO by TDOT for both Washington
and Carter Counties, not
just Johnson City. The MPO staff feels it is important for all the
data to be accessible by the web, even though we do not have an interactive map for the
counties at this time. Occasionally, there is a count station with no
detailed traffic count sheet. This station has been retired. This could
be due to a new road replacing the older road, or a new alignment, or it
was decided traffic counts were no longer needed, so the station number
was retired. Back to top
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