Boone County Public Works Department

Traffic Safety Manual - Boone County, Missouri



Traffic count data is used to determine the frequency of vehicles on county maintained roads.   Counts will be taken on roadway segments between intersections or other pertinent structure that may significantly affect the flow of traffic.   The traffic count data will include, at a minimum, locations, volumes, times, and dates.   Upon implementation of the GIS system, the traffic count information will be posted on a digital map of the County.

10.1  Procedure to Obtain a Traffic Count

There are four situations that may require the County to complete a traffic count on a certain road.   Within each situation, a procedure is outlined to provide traffic count information and/or to complete a traffic count study.   Traffic counts will not be taken during the winter months due to snow removal operations.   These situations and procedures are as follows:

1.   Yearly Scheduled Counts:   Traffic counts will be completed on all County maintained arterial and collector roads once every three years; the traffic counts will be completed on rural roads with a current average daily traffic (ADT) greater than 200 vehicles per day once every three years; and the traffic counts will be completed on the rural roads with an ADT less than 200 vehicles per day once every six years.


2.  Citizen Request:   A citizen will be supplied with the of the most recent traffic count, the date of the traffic count, the location of the traffic count, and the anticipated year of the next count for the particular road requested.   This information will be supplied, in writing, to the citizen.   If the citizen feels that the traffic volume has significantly changed since the date of the latest traffic count, the citizen may request, in writing, for the County to complete a new traffic count of that particular road.   The written request must include the reason the citizen believes the traffic volume has significantly increased since the most recent traffic count.   The County will review the request and if deemed applicable will complete a new traffic count and supply the citizen, in writing, the information of the new traffic study.   If the County does not agree with the citizen’s request, the County will supply, in writing, the reason that the County does not deem the traffic study necessary.


3.   Engineering Safety Study:   A traffic count may be required in conducting an engineering safety study of a road.   The traffic count procedure will follow the requirements of the particular safety study.


4. Joint Boone County/City of Columbia Study :   A traffic count may be completed to assist the City of Columbia on a thoroughfare study.   The traffic count will consist of a 24-hour count on hourly intervals to determine the ADT of County maintained roads near the city limits.   This joint traffic count is completed once every three years.  

10.2   Completion of a Traffic Count

In most situations, the traffic counts will be taken on a seven-day interval and from that information an ADT volume will be derived.   The traffic count information will be recorded on an hourly basis unless the study requires the information to be recorded on the quarter hour basis.   On certain occasions, a 24-hour or a 48-hour recording period with the data recorded on an hour or quarter hour basis may be used.


The tube type counters can be used to determine ADT and, if desired, speed or type of vehicle counted.   The traffic count equipment will be placed near the intersections of roads or in the vicinity of structure anticipated to cause a wide variation in traffic counts.   The equipment will be placed such that it can be secured to a permanent fixture near the roadway.   Consideration should be given to anticipated movement of the vehicles and structures that may affect the traffic flow (i.e. business, subdivision).   A summary of the weather for the week of monitoring should also be recorded.   A map of the area should be sketched.   The map should include, at the minimum, the follow items:


1.   Road names and numbers,

2.  Physical locations of the counters,

3.   GPS locations of the counters,

4.  North arrow, and

5.  Any other structures that may affect the flow of traffic.


The vehicle magnetic imaging (VMI) counters can be used for engineering studies that require more information than provided by the tube type counters.   The VMI counters record the volume, speed, vehicle length classification, road surface temperature, road surface conditions (wet or dry), vehicle presence, and road occupancy.   The VMI counters will only be used on paved roads and the road lanes need to be designated prior to placement of the VMI counters.   As with the tube type counters, the VMI counters should be place near intersections or near structures that are anticipated to cause a variation in traffic flow.   A map, as discussed above, should be used to record the field information.

10.3  Data Output

Once the traffic count information has been obtained, the ADT should be recorded in yearly traffic count database and the information should be updated in the GIS system.   All other information should be used and recorded as needed for the various traffic studies.   A paper copy of the map, the data collector output, and any related correspondence should be placed in the Traffic Count File.

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Last Updated: August 17, 2015