A Team: What are those black cables in the middle of the road?
Q: What are those black tubes that I sometimes see on highways?
A: They are portable traffic counters, placed by the South Carolina Department of Transportation for research purposes. To accommodate various studies on road use and traffic patterns, the DOT manages more than 12,000 traffic counters across the state, most of them portable pneumatic rubber cable.
Many of the tubes are placed in the same location each year, providing a count of the average number of vehicles using that specific location. By using the same location, DOT planners are able to identify changing trends over the years — patterns that are valuable in resolving congestion issues, identifying need for wider roads, or road redesign. The information is essential to long-range traffic planning.
The cables placed in the same location each year are designated as "count stations," DOT spokesman Pete Poore said. Results of the traffic counts are posted on the DOT website and can be accessed by the public.
In addition to the designated stations, the department counts traffic at random locations in an effort to identify new problems.
Single-tube counters, which are less expensive and easier to install, are used most often. They measure the number of vehicles over a 24-hour period.
At times, two parallel cables are deployed. That enables the DOT to determine the speed and type of vehicle (car, bus, or 18-wheel truck). The two-tube counters, also known as Continuous Count Stations (CCS), count vehicles 24 hours a day, 7 days a week.
Nationally, some form of traffic counters have been part of traffic planning since 1937. In the early days, people were paid to manually count the number of cars passing by.
From the DOT's counter data page, visitors can access historical averages at any station.
Here is a link to the South Carolina DOT traffic count page:
Reporters Georgie Silvarole, Abe Hardesty and Mike Ellis make up the A Team. Their weekly column is dedicated to answering any and all of our readers' questions. To submit a question, email firstname.lastname@example.org or send a letter to the Independent Mail at 1000 Williamston Road, Anderson, SC 29621. The question-and-answer articles will appear in print on Saturdays.